CHAP. 1. Of the Anatomy of the Brain.

THE topmost part or Olla of the Cranium be­ing removed, the first part of the Brain that comes in view is the Dura Mater, which, with the subjacent Pia Mater, is accounted only an im­proper part of the Brain, strictly so called, however of great use in many respects to it.

'Tis by Spigelius and other Anato­mists reckon'd, and I think not unde­servedly, the thickest and hardest Membrane of the whole Body, enclo­sing the whole Brain, properly so called, somewhat losely, sticking al­most [Page]inseparably to the Basis of the Cranium, and to the top and sides, un­der the Coronal, Sagittal, and Lam­docid Sutures, very fast by the Sinus's whose description will come in ano­ther place.

In some places of the upper part of the Cranium, which on each side of the Sagittal Suture or Vertex are called Ossa Bregmatis, it adheres not to the Bone, notwithstanding the positive Opinion of Van Roonhuyse, Roonh. p. 149. in his Lei­ter to Du Foy, to the contrary, who for that very reason would fain take away in a great measure the use of the Trepan and Trefoyne, and altogether the use of the Instrument called De­cussorium, which skilful Surgeons do often make use of to make room for the discharge of subsided matter below the fractur'd place in many Accidents of the Brain.

'Tis very discernably double, as Columbus and several others formerly, Col. p. 348 and Vieussenius lately, have observed, having very strong and large Fibres on the inside, but very small, Vienss. p. 3. and hardly visible, on that side next the Skull; as appeared to me, after ha­ving first let it lye a little time in bol­ling or at least very scalding Water.

But as to the distribution of the double sort of Fibres on each side this Membrane, I could not by any means find them agreeing with the descripti­on Vieussenius hath given of them, as running in an oblique semicircular manner, externally from before back­wards, and in the same figure internally from behind forwards; but far other­wise, on the inside, where they are very strong, they seem manifestly to have three originals from the top part of the Processus Falcatus, before, be­hind, and in its middle; those before running in a curved manner back­wards, half the length, and a great width of the Dura Mater, and those behind running after the same man­ner forwardly with this difference, that a great number of them bend soon after their rise from that process in a kind of a semilunary way to it again a little on this side the rise of the middle Series of Fibres, others of them making a bigger arch after having stretched themselves wider upon the Dura Mater, bend back again to, and terminate in the Falx a little beyond the rise of the aforesaid middle Series of Fibres.

Those from the middle part of the Falx run backwardly, but less curved than the rest, terminating as the Fi­bres which arise backwardly do, at some distance from the Process in the inward Superficies of the Dura Mater.

As to those belonging to the exer­nal side or second Lamina of the Dura Mater, they are extream small and obscure, running from behind for­wards.

Besides these, there are no less re­markable ones belonging to the Falx it self, of two sorts of Orders, the one running streight about half the length of it, on its upper part, from before backwards, the other transverse, from the inferiour or fifth Sinus to the su­periour or third, on the hinder part of the Process, and are most conspi­cuous there, as the other are towards its foremost part.

As to the Use of those Fibres, it may be remembred that this Mem­brane consists of two Lamina's, be­tween which the Veins which reduce the Blood from the Arteries, which furnish the whole Brain with it, run for some space after the manner of the Ureters in the Bladder, in large [Page 5]Trunks, before they enter the Sinus; so that the Fibrous Constitution of this Membrane here, where the Blood­vessels are largest (together with the curved entrance of them into the Si­nus, especially in an erect position of the Body) do the office of Valves, support the weight, and promote the ascent of the Blood. But that which is most considerable, is this, That if the inward Lamina of this part, which makes the inferiour and lateral part of the Sinus, was not in some mea­sure furnish'd with additional strength on this side suitable to that which it hath on the other, by reason of its cohesion to the Skull, the Blood which is continually running through it with no small rapidity, especially in great plenitude of the Vessels or preternatural Ebulitions, would fre­quently burst out, or at least cause such distentions as could not but be very injurious to a part so very exquisitely sensible; yet notwith­standing, tho' Nature seems plainly to have made a double provision against such Accidents, by the transverse Li­gaments within the Sinus, and these strong and numerous Fibres without, I have rarely open'd any strangled [Page 6]Body, where some such Rupture, or at least Distention, hath not hapned.

This Membrane hath plenty of Nerves from the foremost Branch of the fifth Pair, and is thereby made very sensible, so that from any mo­lestation given it by the ill Crasis or undue motion of the Blood, it be­comes accordingly affected. And as the various distribution of Fibres be­fore described serve in a natural estate to give a kind of springiness to the Vessels, whose Coats are extended by the Blood as they run between the Laminae of this Membrane, to the end the same may be the more readily circulated through them; so in a preternatural estate, no doubt, they are subject to Spasms, which may re­tard the course of the Blood in such sort, that in some kind of violent Headachs, where the Membrane is affected through overfulness of Blood, and particularly in those which are wont to proceed from Vapours (so called) or Convulsive Motions of Nervous parts, we often observe a fix­ed ruddiness in the Face, attended with a kind of stiffness and soreness in the Eyes, proceeding doubtless from a stagnation in some measure of the [Page 7]Humours in those parts, through the too slow passage of them into the re­ductory Vessels or Sinus's. And to this preternatural affection of the Si­nus's may certainly many other ill Symptoms of the Brain be imputed, and not to any irregular Syslole and Diastole of the Membrane it self, oc­casion'd through any convulsive or paralytical state thereof, as that cu­rious Speculatist Dr. Mayow hath affir­med, Mayow. Tr. 4. p. 49. seeing not any living Dissection hath ever been found to give Autho­rity to any such Hypothesis.

The First Process of the Dura Mater.It hath two Processes, the first of which arises from that part of the Os Ethmoeides, called Crista Galli, and is extended from thence backwards, as far as the concourse of the four grea­ter Sinus's commonly called Torcular Herophili, in the figure of a Sicle, whence it hath that denomination of Falx, and by reason of the strict con­nexion it hath by certain Membra­nous Fibres with the Cranium in those places which are immediately under the Sutures, and with the Brain it self, by the intervention of the Pia Mater, (to which it is joyned both by the in­tervention of large Blood-vessels, pro­pagated thence to the longitudinal [Page 8]and lateral Sinus's, and certain car­nous Adnascencies, as it descends down betwixt the two Hemispheres of the Brain, and afterward at its approach to the back of the Corpus Callosum, (over which that Membrance is loose­ly expanded) both by continuity of its Membranous Substance and Rami­fications of Blood-vessels, terminating in the fifth Sinus, at the bottom of the Process, so that in a Diseased Brain I once saw it drawn up the length of an Inch from the said Corpus Callosum, in the exact form of a membranous thin Production, continued to the fifth Sinus running at the bottom of this Process,) it keeps the Brain suspended in such a natural confor­mation, that it needs not, to that in­ternal part by the Ancients call'd For­nix, nor that by Vieussenius of late subslituted in the room of it, call'd Corpus Callosum, for its support.

Another Use it hath is, partly to defend the Cerebellum from Compres­sion, to which, by its connexion with the Galli Crista, it doth not a little contribute, but chiefly the two He­mispheres of the Brain from the like Injury from each other, upon its vari­ous position in Sleep or otherwise; [Page 9]and therefore is wanting in many other Creatures, as Calves, Sheep, &c. which not only Sleep less, but for the most part in a less injurious posture.

The Second Process of the Dura Mater.The second is that which arising so forwardly as from the hindermost Process of the Wedglike Bone, which composes the back and uppermost part only of the Sella Equina; it passes up betwixt the Cerebrum and Cerebellum, all the way adhering to the internal Eminencies of the Ossa Petrosa to the lateral Sinus's, by which means not only the Cerebel­lum immediately, as is commonly observed, but consequently all the Parts from the beginning of the fourth Sinus, or the Glandula Pinealis, to the last Foramen of the Skull, (viz.) the Caudex Medullaris, with its Appendi­ces the Nates and Testes, (which be­ing placed upon the upper part of the Medulla Oblongata, make a sort of an Isthmus betwixt the Cerebrum and Ce­rebellum) together with the Nerves proceeding out of it, are defended from the injurious pressure of the hin­der Limbs of the Brain.

CHAP. II. Of the Pia Mater.

THE Second Integument of the Brain, commonly called Pia or Tenuis Mater, by Galen and many others, Choroeides, from its likeness in substance and ramification of Blood-vessels to that Membrane of the Se­condines call'd Chorion, with much more reason than Vesalius, on behalf of the Plexus Choroeides it self ad­vances against it; was by all the An­cients look'd upon as its only other Integument, being a very thin and pellucid Membrane, co-extended with the Brain it self, not only in its out­ward but inward structure too, as likewise through all its Plicatures, In­terstices, and Cavities, even over the Corpus Callosum it self, tho' loosely, as hath been already observ'd, not­withstanding the great Vesalius af­firms the contrary: Ves [...]al. p. 778. par. 2. Which Membrane also a chance cut in pareing the top­part of the Brain down to the lateral Ventricles with a Razor, in a Body I lately had, gave me an opportunity [Page 11]of showing as fair in those Ventricles as the largest Membrane of the whole Body, to several who stood by, no­withstanding Molinetti, Mol. p. 7 [...]. who laughs at all that pretend to have found any such thing, affirms the contrary.

But this is to be enquir'd for either in recent Bodies, or such who have before death been, thro' some Disea­ses, fill'd with extravasated Serum, as Dropsies, Stoppage of Ʋrine, some sort of Apoplexies, or the like: That way which in want of the other opportu­nities discovers it best, is the separa­ting the Septum Lucidum near to its rise, which is just from the Fornix, where it arises from its two Roots, near to which place the Medulla of the Brain begins to advance into the Corpora Striata; for from thence for above half way of its passage back­ward toward the hinder limbs of the Brain, it continues hollow, and, I am apt to think, is but a Duplicature of this part, tho' it may be somewhat medullary, and therefore, by reason of its transparency, hath the Name of Septum Lucidum.

This Opinion of the Ancients, of its being the only other, and that a single Integument of the Brain, was [Page 12]equally receiv'd for Truth by the late two learned and curious Anatomists Willis and Vieussenius, together with all the other modern Writers, except Bidloo and Bohn, both which affirm, Bid. Tab. 8 f. 5, g. Bohn p. 333 they have found another distinct membranous Integument of the Brain coming betwixt the other outward Dura, and inward Pia Mater, the one three hours, the other fifteen days after death; and by them both recko­ned the original of the second pro­per Integument of the Spinal Mar­row which Tulpius first discovered, Tulp. cent. 1 obs. 29. Vienssen. p. 143. par. 2. and Vieussenius supposes to be a Dupli­cature of the Pia Mater in that part only.

Now, that there was a middle Membrane in some parts of the Brain, and particularly at the Basis of the Cerebellum, from whence it's conti­nued down to the Spinal Marrow, constituting the second proper Inte­gument of that part as afore-mentio­ned, I had long since-observed; but whether it be another absolute di­stinct Membrane from that other sub­jacent one, by the aforesaid Authors properly named the Pia Mater, and common to the Spinal Marrow with the Brain it self, like as is this other [Page 13]second middle one too, or only one and the same Membrane double, as consisting of two Lamina's, may well be doubted of.

Wherefore, for satisfaction concer­ning this difficulty, I have lately made the strictest enquiry possible, and that in a subject most likely to afford a decision in such a Controversie, and this was an Human Brain extreamly hydropical, where there was no Ca­vity or Interstice, without abundance of Water extravasated, insomuch that where ever, according to the natural construction of Parts, there was any larger than ordinary duplicature of this Membrane, as there are at the end of the Calamus Scriptorius, be­twixt the superincumbent Cerebellum and Medulla Spinalis, in the Isthmus or space betwixt the Cerebrum and Cere­bellum, upon the Processes called Nates and Testes, in the depressed part also of the Brain, between the beginning of the Annular Process, and the first appearance or coming out of the Ol­factory Nerves, by Vesalius taken notice of and called a Process of the Pia Mater, Visal. p. 794 there was found a great deal of Water distending this Dupli­cature much beyond its natural li­mits; [Page 14]so that by way of consequence, if these Cavities were only Interstices of two different Membranes distinct­ly investing the Brain, and not a Du­plicature only of one and the same, the Water would then probably have insinuated it self betwixt them, and made them to have appear'd far diffe­rent from what they did, agreeable to what it hath often been found to do in some Dropsies of the Belly, where the Water hath been found so to have divided or parted the double Mem­brane of that Region call'd Perito­neum, as to have render'd it capable of containing the quantity of fifteen Gallons of Water, and upon a dis­charge of the same after death, by cutting the external Lamina of that Membrane, the other inward one be­ing yet (unknown to the Dissecter) left whole, to have imposed upon the Spectators, and those very sagacious ones, so as that at first sight, till after having recollected themselves, Job Mei [...]r. Obs. 52. and divided the other second Lamina too, they thought the Bowels of this part to have been wanting; but contrary to this Event, in this Subject I found this Membrane entire, and free from any divulsion throughout its whole [Page 15]circumference, excepting the places afore taken notice of. However, sup­posing the like conformation here in this with the Membranes of the other parts, I attempted to divide it, and did so successfully in many parts of it, but most readily in the beginning of the superficial Plicatures of the corti­cal part of the Brain, where there are naturally small Interstices, betwixt which many of the Blood-vessels creep into and immerge themselves in the cortical and medullary parts thereof: So that I think there cannot remain any further scruple of its being only a double, and not two distinct Mem­branes of the Brain.

Bidloo very truly observes this first or middle Membrane, by him so cal­led, by me only the first, or one La­mina of a double Membrane, to be thinner than the Dura Mater above it, and thicker than the other Membrane or Lamina under it; which last most properly it is that insinuates it self through all the close Plicatures of the Brain, and that, as by frequent inspe­ction I have often observed, not in a continuous, but rather retiform con­texture, and so, by such as love hard words, or terms of Art, may be [Page 16]called after the same name of that Membrane investing the crystalline Humour of the Eye, Arachnoeides.

The Advantages accrueing to the whole through such a disposition of this part, as hath already been obser­ved, are very considerable, inasmuch as that thereby first of all it becomes not only an Integument of inclosure, on behalf of the Brain, and the Blood-vessels belonging to it in general, but of expansion for Strength too, where the peculiar structure of Parts, in such places as were before mentioned, re­quire it.

As to the first, the Brain is not only kept more warm, close, and compact, and better defended on its depending part from the asperity of the Bone it lies upon, but the Vessels hereby more strongly supported, and it self secured from being broken or torn, whilst between its duplicature they climb up into the Brain, whose deli­cate tender Fibres must otherwise of necessity have suffer'd violence by the largeness and pulsation of the Arteries, together with the weight of them, and the other reductory Vessel, from which the Sinus's meet them.

Nextly, as it is an Integument of Expansion in the places before men­tion'd, that tender small part the In­fundibulum, where it quits the Brain, in order to its passage into the Glan­dula Pituitaria, by the circumtension of this outward Lamina, is fortified upon any violent Accident from dis­ruption, and the Brain and Medulla Oblongata, in those places where they are only loosely contiguous, are bet­ter preserved in their natural due connexion; all which Advantages, inasmuch as they may more reasona­bly be ascribed to one double Mem­brane than two single ones, tho' of the like strength when joyned fast together, may not unreasonably be thought to argue for the duplicature of this Membrane exclusively, to the introduction of a third or new one.

Lastly, as to what concerns the Glandes and Plexus's which Dr. Wil­lis affirms to be scatter'd all over this Membrane; as to the former, Will. p. 26. col. 1. I could never see them, but I have seen the external Superficies of the cortical part of the Brain, in strangled Bo­dies, appear glandulous very plainly, through this transparent Integu­ment, which upon bare inspection, [Page 18]without further enquiry, might easily impose upon the less cautious Spe­ctator.

As to the latter, the Plexus's, and distribution of Blood-vessels from them, after a separation of the serous gross part of the Blood in the afore­mentioned supposed Glandules, (ac­cording to that learned person's con­jecture) into the substance of the Brain, in order to produce the finer Animal Spirits; I cannot but look upon it altogether conjectural, till such time as not only the Glandes, but their excretory Ducts also, together with the Emunctories where the sup­posed excrementitious Juice is eli­minated, (lymphatick or reductory Glandes (if they could be found) ne­ver having been by Nature designed to any such use) be first discovered.

Blood-ves­sels of the Pia Mater.This Membrane hath Blood-vessels of two sorts.

Of the first are these properly be­longing to the Brain it self, which, as it hath already been observ'd, it doth as it were conduct through its Dupli­cature, in their passage allowing them thereby the opportunity of growing extreamly fine, after many serpentine twinings towards their capillary Ex­tremities, [Page 19]before they are protended into the Brain it self, Bid. Tab. 8. f. 5. l. M and those are chiefly spread all-along upon the un­der or second Lamina of this Mem­brane. Ib. l. G.

The second are those which be­long to this part it self, for its own nourishment, and these I found upon diligent inspection, whilst I separated its second Lamina spread plentifully upon the inside of the outermost or first Lamina, and both these you will find very well delineated in the places quoted in Bidloo.

This Duplicature is also very plain­ly communicated to all the Nerves both within and without the Cranium, making by its outward Lamina a se­cond Integument under the first from the Dura Mater to the whole [...]ascicu­lus of Nerves, and a third by its in­ward Lamina, which yields an involu­crum or covering to each single Fi­brilla, which collectively make up the whole Nervous Body it self, thro' the admirable fineness of which Mem­brane investing those medullary Fi­brils, altogether insensible of them­selves, it happens there is such a nimble consent betwixt part and part, and betwixt all and the Brain it self.

CHAP. III. Of the Vessels belonging to the Brain in general.

THE Vessels belonging to this part in common with the rest of the Body, though in reality but one continued Canal variously modified, yet, through the diversity of Fluids they contain, go common­ly under the denomination of Ar­teries, Veins, Sinus's, and Lymphae­ducts, and not without good reason, perhaps, the Nerves may be in some sence of the same kind too.

The two first of these may, with relation to their different distributi­on, be deservedly consider'd in a two-fold respect, either as they be­long to the first Integument of the Brain, or the Brain, properly so called, it self.

The Arteries therefore belonging to this part called Dura Mater, or first Integument, are three fair Bran­ches on each side.

The first and foremost of which are sent out from the Carotid Arte­ry, whilst it remains in the fourth hole of the Cranium, FIG. 2. hh. and are pro­pagated chiefly through the fore­most part of the bottom of the Dura Mater, as in the Figure delineated, but greatly mistaken by Dr. Willis, Willis p. 2. col. 2. wepf. p. 10 [...] par. 2. perhaps taking it upon trust from Wepfer, equally with himself there­in mistaken; who describes it for a small branch of the Carotid Arte­ry, that runs betwixt the two first Lobes of the Brain, which instead of coming out of the Bone of the Forehead, as he would have it, goes into it without lending any branches to this Membrane at all, being truly delineated and described by the aforemention'd accurate Vieussenius. Vieuss. Tab. 17. dd, bb. p. 32. par. 4. Wepf. p. 101

And that this Artery was not on­ly mistaken by, but unknown to the aforesaid Wepfer, is plain, seeing he says, that from the very styliform Process, where the Carotid Artery does indeed enter the long Canal, to the place where it perforates the Dura Mater to enter the Brain, there is not one Branch sent out from it; which Error, by injecting with Wax, which keeps longer in, [Page 22]and shews the Vessels much better than small tinged Liquors, had very easily been avoided.

The second Branch of Arteries ascend into the Dura Mater by the sixth hole of the Cranium, FIG. 2. ll. together with a Branch of the internal Jugu­lar Vein, and are dispersed laterally all over the fore-part of this Mem­brane, as far as the very Sinus Lon­gitudinalis, (which nevertheless it enters not, as there will be occa­sion to take notice of hereafter) as in the Figure delineated.

The third Branch of Arteries climb into the Dura Mater by the eighth hole of the Calvaria, toge­ther with a small reductory Branch of the Vertebral Vein, FIG. 2. kk. where the lateral Sinus's enter the internal Jugular (which occasion'd the Inge­nious Highmore erroneously to be­lieve it enter'd the very lateral Si­nus it self) and the eighth pair of Nerves pass out of the Cranium, Highmore, p. 206. par. 1. which passage of this Artery is not hitherto described by any that I know of; neither have I ever seen it figured, Vieuss. tab. 1 kk. but in Vieussenius's first Cut, and there but very faintly.

It arises from the external Bran­ches of the Vertebral Artery, Vieuss. tab. 8. f. i. c. Barthol. p. 431. par. ul [...]. accor­ding to Vieussenius, but Bartholine makes it to be a slip of the Carotid Artery, calling it the lesser Branch thereof; wherein he is mistaken.

The Veins of the Dura Mater.As to the Veins, Riol. p. 252 par. 2. Will. p. 2. col. 2. par. 6. Riolane, and af­ter him Willis, seems to say this Membrane hath none; for tho' the latter hath this obscure expression of them, Tam crebris Venarum propagi­nibus quam Arteriarum nusquam con­sita est; speaking of the Crassa Me­ninx, by which we might guess he thought it had some, Will. p. 22. col. 1. par. 4. yet in another place he plainly substitutes the Si­nus's for the reductory Vessels, as well on behalf of this Membrane as the Brain it self; as appears plain enough in the Page noted.

Vieussenius indeed allows Veins to this part, and says, Vieuss. p. 31 par. 3. they all-along accompany the Arteries, and after­ward terminate, according to Veslin­gus, Vesling. p. 210. Vieuss. p. 4. par. 2. in the internal Jugular; yet in another place he says, some of the Venal Branches discharge the Blood into the Sinus Longitudinalis. Which last is a flat contradiction to the place foregoing, inasmuch as in that he says, they accompany the Arteries [Page 24]all-along after the same manner of distribution or ramification; which, if so, who sees not that they must needs grow capillary towards the Sinus, and consequently be uncapa­ble of reducing the Blood into them, all reductory Vessels being always capillary in the place from which, and not to which, they bring that which they contain.

Now therefore, neither what the one nor the other says can possibly be true; for, as to the former the learned Dr. Willis, if his Assertion was good, it must of necessity fol­low, that all the Arteries dispersed thro' this Membrane must terminate in some of the Sinus's, otherwise there will want a reductory Vessel; the first of which is contrary to ocu­lar demonstration, the last to com­mon reason.

As to Vieussenius the latter, be­sides what hath been already said against him, if what he says in the place aforecited be true, that the Veins of the Dura Mater run con­comitantly along with the Arteries, then they must of necessity answer the ends of other Veins throughout the whole Body, in reducing the [Page 25]Blood adduced by the Arteries, un­less the Arteries they accompany dis­charge their Blood into the Sinusses, (which, as hereafter shall be shown, they plainly do not) for otherwise, seeing they both grow capillary in their ascent from the Basis of the Cranium, they must necessarily be both adductory Vessels, than which, by the Laws of Circulation, there can be no greater an Absurdity.

Wepfer not knowing of these Veins, was forced to think, and consequent­ly to affirm, That the Arteries leave the Dura Mater in their extremities, and terminate in the Pia Mater, and so have their Blood reduced by the Veins there; but this is evidently not so to the Eye of any who heedfully separates this Membrane from the other.

Before therefore I proceed to the description of the Blood-vessels be­longing to the Brain it self, which by the exactness of method I ought to do, I hope it may be pardonable, if I make a short enquiry after the unac­custom'd distribution of Blood-vessels Nature hath furnish'd the Brain in general with, and the Reasons of its procedure therein.

The Truth then concerning this affair, is, That contrary to what hath hitherto been observed, the Blood-vessels belonging to this part in gene­ral, as hath already been observed, are of two sorts, the one belonging to the Brain it self, the other to its out­most Integuments.

Now, as to the first, 'tis observa­ble, that the Veins enter not the Brain, nor run concomitantly, like as in other parts of the Body, with the Arteries, (the carotid entring at the fourth hole in the Basis of the Skull, and the internal Jugular at the eighth; the Vertebral Artery at the last and largest hole of the Skull, and the Vertebral Vein at the ninth (which Vieussenius mistakenly calls the tenth) thro' which it runs into the internal Jugular, Vie [...]ssen. p. 163. par. 3. at that Veins entrance into the round hole at the bottom of the Skull, under the Styli­form Process, where the Sinus Latera­lis meets it) where after having ad­vanc'd into certain venous producti­ons called Sinus's, they descend from thence in large Trunks, growing ca­pillary all-along in their passage till they meet the Extremities of the Ar­teries, and are indeed no other than [Page 27]meer Branches of the Sinus's, and consequently I look upon the Si­nus's themselves no other than large Veins.

The common reason all modern Authors give for this different distri­bution of Blood-vessels belonging to the Brain, from the other parts of the Body, is, that it may receive an equal warmth at the top as at the bottom, as being thereby very much assisted in the production of Animal Spirits in an equal proportion all over; and that it is so may very well be granted: but, that Nature had yet another provident Intention, will be as evident, if we consider, that if the Veins had ascended with the Arteries thro' the holes in the bot­tom of the Cranium, upon all great Ebulitions of the Blood, the pulsation of the Arteries would in that Stricture of the Vessels made by the Bone, of necessity hinder the freedom of its return by the Veins, and consequent­ly occasion a stagnation of Blood through the whole Brain, to the ut­ter subversion of all its faculties, no­thing being more certain, than that upon any considerable abatement of circulation there presently happens [Page 28]by way of restagnation, a secession of the watery and thin from the more gross and red part of the Blood.

The other way of the Veins en­tring the Brain ( viz. those appertain­ing to its outward Integument, one at the sixth hole of the Basis of the Cranium, the other at the eighth, as aforesaid) is, their ascent with the Arteries after a quite different man­ner from the former, even to their capillary Extremities; a manifest in­dication that they serve for the re­duction of so much Blood from the Dura Mater as the aforesaid sort of Vessels, the Arteries, have brought thither; and although by reason of their smallness Nature seems not to have been so sollicitous in avoiding the Inconvenience supposed to have follow'd, upon the Artery's entring the same hole with the Veins, taken notice of in the preceding Case, where they are very large, and consequent­ly the Effect might prove much more injurious, yet Nature hath not been wanting in providing a Reme­dy against it; as will plainly appear in the following Pages.

From this manner of their entring the Brain at the same inlet of the Skull with the Arteries, may, for ought I know, be very rationally accounted for that violent trouble­some Noise which many, in Distem­pers arising from the turgescency of the Blood, causing a preternatural beating of the Arteries, do so much complain of; a Symptom happening from the Stricture before mention'd which the unyielding circumference of the Bone occasions upon the dif­ferent Blood-vessels entring at one and the same Foramen, to which effect also the nearness of the Os Pe­trosum, through which the Hearing Nerves do pass to this hole, which is in that part of the Wedglike Bone that joyns to, or is conterminous with it, does not a little contribute.

To the same cause, in some measure doubtless, may be ascribed the fre­quent Headachs happening in Fea­vers, the Artery then so swelling and compressing the Vein against the edges of the Bone, that the Blood can­not be returned back through it in a due proportion, and consequently by its stagnation the Membrane be­comes inflamed and painful.

So that conformable to what hath already been taken notice of concerning the wise contrivance of Nature, in ordering the different distribution of the Blood-vessels, so as to avoid the Inconveniencies which might accrew to the Brain by compression of the reductory Vessels, occasion'd through their entrance at one and the same hole with the Arteries; it seems very much worth our observing, that be­sides the Veins of the Dura Mater, which enter the Cranium together with the Arteries, as hath before been mention'd, there are also seve­ral others belonging to this Mem­brane, having their rise at, and their descent after a very remarkable manner, from a Vein hereafter to be describ'd on each side of the Longi­tudinal Sinus, as you may see in the Figure, FIG. 4. dd, nn, &c. and consequently must grow capillary in their descent down from it, after a quite contrary man­ner to the other; and these do visi­bly inosculate with some of the Ex­tremities of the aforesaid capillary Arteries, after the same manner as those larger Veins belonging to the Pia Mater do with the Arteries [Page 31]belonging to the Brain and it, by which means it so falls out, that a considerable part of that Blood brought up by the Meninx Arte­ries, is carried back by these Veins, to the end that, especially in all preternatural swelling of the Blood, the inconvenience of Compression and all its ill consequences happen­ing, by reason of an overfulness of these Vessels, may be in a great measure avoided.

CHAP. IV. Of the Veins belonging to the Brain it self.

AFTER this short digression, by order of Method, the Blood-vessels belonging properly to the Brain it self, fall under consideration.

The curious Anatomist Malpighius, Malp. de Cereb. p. 6. par. 2. De Cort. Cereb. p 81 par. 2. in his Letter to Fracassatus, says, they bear a third proportion to those of the whole Body; and for what rea­son, seeing, seeing the part it self bears not the same proportion to the whole, it is so, it will be worth our while to enquire hereafter.

These are either Arteries or Veins. The former go under the name of Carotid and Vertebral.

The first of which, after a curved passage (which is very well expressed in a Fig. Willis p. 29. Fig. 1. of Dr. Willis) from the place where it begins to enter the Basis of the Cranium (which is from the Styli­form Process of the Os Petrosum) to the place where, on the inside, they pass through the Dura Mater, and ascend into the Brain, (which is at the [Page 33]foremost internal Process of the Os Cuneiforme) there is very near an inch and an half distance. I say, after this crooked passage into the Brain, they are propagated quite through its sub­stance, having first divested them­selves of that thick Coat borrowed of the Dura Mater during their stay in the passage aforementioned; but not without the mediation or interven­tion of the Pia Mater, which Mem­brane all the Branches of the aforesaid, as well as the Vertebral Artery, more or less first prop themselves upon, be­fore they enter on and disperse them­selves through the substance of the Brain it self, and is very finely expres­sed in a Cut of Placentinus, Sig. p. 179 Mol. p. 77. Marchetti, p. 191. par. 5. at the end of Spigelius; insomuch that Molinetti (with whom also agrees Marchetti) looks upon it as only a production of those numerous Vessels; whereas all those little ramifications both of the Carotid and Vertebral Arteries, viz. those: from the carotid Artery, which as soon as it gets through the Dura Mater, and parts with its bor­rowed Coat, are sent to the Vieussen. p. 35. par. 1. p 34. par. 6. Infun­dibulum, Tab. 17. c c. Olfactory, and Ib. g g. Optick Nerves, together with those other of the Vertebral Artery which accom­pany [Page 34]pany the Vicussen. p. 35. par. 1. third, Ibid. fourth, Tab. 17. p p. 35. par. 1. fifth, Tab. 17. TT. Tab. 4. sixth, h. p. 35. par. 1. seventh, Tab. 17. Fig. 2. Tab. 4. h h. eighth, Ib. Fig. 2. ninth, and Tab. 4. h h. tenth pairs of Nerves, inasmuch as they en­ter not the Brain it self, are altogether exempt from that Membrane; any of which now-mention'd Blood-vessels you either find delineated in Vieusse­nius's 17th Table, or mention'd in some other place of his Book, by those Directions here placed in the margin; all which, tho' existent in Nature, are nevertheless there painted too stiff and formal (I am afraid by guess) inasmuch as that without an injection of Mercury (except those two which belong to the Olfactory and Optick Nerves) they do rarely come to sight in any form at all, Wax being over gross a body to en­ter such minute Vessels as those are; whereas by an injection with Mercu­ry I find scarce any Nerves but what hath some such small ramifications of Blood-vessels in them.

To go about to describe distinctly the whole ramification of Arteries through this part, which as was be­fore noted, is here more remarkable for number and size than in any other part of the Body, would not only be to do what in a great measure hath [Page 35]been already done by Vieussenius, in his sixth Chapter, but seem to have also in it much more of oftentation than use.

I shall therefore only take notice of such propagations of them, as are either remarkable for magnitude, some curiosity of Structure, or useful design of Nature.

And of this sort may well be estee­med the Vertebral Artery, next after the Carotid, which hath already been described, as entering the Brain at the last and largest Foramen of the Skull, contrary to what Dr. Willis, Willis, p. 29. col. 1. par. 2. and before him Wepfer, affirms, coming thither on each side out of the hole in the transverse Process of the first Vertebra of the Neck, after a very remarkable curved manner, as you see in the Figure, Fio. 1. E [...] (and by no means like to the delineation and de­scription given by Dr. Lower and Dr. Willis,) ascending laterally upon the Medulla Oblongata as far as the beginning of the Processus Annularis, where they meet together in one single Trunk continuing so the length thereof, Vieussen. Tab. 4. bb. by Vieussenius call'd Arteria Cervicalis, after which they either send forth two Branches, or re­ceive two from the carotid Artery, by [Page 36]means whereof there is a communica­tion betwixt these two large Blood-vessels, and that of great use and bene­fit to the Brain, for by this means it happens, that if even three of the four great Arteries which furnish this part with Blood, were totally obstructed, there would yet be a way left for a competent supply from the other un­obstructed fourth. These I call the Communicant branches, very ill pointed in Bidloo's ninth Table, but very well in Vieussenius's fourth; as may plain­ly appear here in the Figure taken exactly from Nature it self. FIG. I. dd

The structure and sinallness of these Arteries seem to suggest two, yet fur­ther, provident Intentions of Nature.

The first is the same it hath ex­pressed in several other places, as in the ascent of the Blood by the Carotid Arteries, both which enter the Brain in a crooked line, the first at the fourth hole of the Basis of the Skull, the second from the hole in the transverse process of the first Verte­bra of the Neck, after the manner already in both places described. So in the like manner here, by the nar­rowness of these Branches, the Blood is in a great measure retarded in its [Page 37]motion to the carotid Artery, and by consequence to the Brain it self, which, for Reasons hereafter to be given in describing the Sinus's, would other­wise be in great danger of being over­flowed with extravasated and restag­nant Blood.

The second is, a forcing the Blood more plentifully into the Spinal Ar­tery, with which, tho' through the conical structure of the Arteries in common it cannot be altogether un­furnish'd, yet by its perfectly-reflexed position, would have it very scantily, were it not that by reason of the nar­rowness of the aforesaid Communicant-branches betwixt the two great Ar­teries, the Blood was driven back in a sort of a retrograde motion.

'Tis true, there is a conformation of Arteries something like this, tho' not altogether in the mammary and epigastrick Branches; but 'tis worth noting, that in both these places the main Artery from which these Bran­ches spring is much more taper or conical, Ibid. p. c c and the succeeding export­ing Vessels far less both in number and size than those of the carotid Ar­tery here, whose foremost and hin­der lateral ramifications between the [Page 38]Lobes of the Brain, bear an over-proportion to the Trunks from whence they come, and consequently must, according to the aforesaid ob­servation of Malpighius,) in his Letter to Fracassatus, receive the blood brought thither far more freely and plentifully.

Besides, the Cervical Artery here is so far from being Conical, that be­ing made up of two vertebral Arteries joyning together, it is much wider than either of them single, as appears plain­ly in the Figure, FIG. 1. g. and consequently would have carried away the Blood forwardly from the Spinal Artery more freely, had not Nature order'd the Structure of Vessels after another manner here than it does in other parts of the Body, where there is not the same necessity of contrivance.

One more Branch I take leave to mention only upon the score of its never hitherto having been taken notice of by any, and that's a small Artery attended with a Vein passing through the lateral part of the Os Cu­neiforme, (which constitutes the back part of the Orbite of the Eye, just under a very little Process of that Bone, (which either by reason of its [Page 39]size hath escaped being seen, or in­considerable use, was never before, as far as I know, thought worth the mentioning;) and this, upon raising the fore Lobes of the Brain, offers it self to the Eye of any heedful Ob­server.

CHAP. V. Of the Sinus's belonging to the Brain.

A Third sort of Vessels offer them­selves next to our considerati­on, under the general name of Si­nus's.

These formerly were reckon'd only four, to which Vesalius added a fifth at the bottom of the Falx, Vesal. p. 758 Fig. 3. F. by him only call'd a Vein, which tho' fre­quently found, yet in some Subjects is wanting. Bourd. p. 105. par. 2. Bourdon mentions two more at the bottom of each side the side the second Process of the Dura Mater, [Page 40]under the lateral ones, which I never saw but once, and I am apt to think with Vieussenius, are most commonly wanting.

Vieussenius describes four more, Vieuss. p. 6. par. 5. Fall. tom. 1. p 114. Vid. Vid. p. 117. cap. 10. p 310. cap. 11. which I find long before taken notice of, and exactly describ'd by Falloppius, and after him, tho' but rudely, by that laborious Collector Vidus Vi­dius.

I think I can shew one more, but be their number what it will, I judge it reasonable to look upon them no other than Veins, whether we consi­der them in respect to either Office or Structure. All the business is, to consider and shew for what end they appear as such large Channels into which all the Veins of the Brain, like so many small Rivulets after an unusual manner do empty themselves; and that I will endeavour to do after having first shown their several re­spective situations.

The first two are called Laterales, FIG 4. BB. which run within a strong duplicature of the hinder Process of the Dura Ma­ter, down upon the Os Occipitale over the Cerebellum, till in their further de­scent, after a tortuous manner, upon the lower production of the Ossa Pe­trosa [Page 41]they wind under them in order to their passage out of the Cranium at the eighth hole, FIG. 2. CC. common to the eighth pair of Nerves going out, Ibid. bb. the third Branch of Arteries belonging to the Dura Mater, and the internal Jugular coming in, which is through two round bony Cells in the Os Pe­trosa, Ibid. L. just under the Styloeid Processes into the internal Jugular Vein, into which, together with the Vertebral, all the rest of the Veins and Sinus's belonging to the Brain discharge the refluent Blood.

The next is called the third or longitudinal one, FIG. 4. AA, &c. from its rise at the bony Process called Crista Galli, and progress the whole length of the Brain to the hinder and somewhat declining part of the occipital Bone, where it seems to be cleft into the two lateral ones.

Into this third Sinus not only the internal Veins of the Brain it self are inserted, but also some of those be­longing to its outward Integuments, which Falloppius first, Fallop. tom. 1. p. 82. par. 3 Vitus. p. 10. par. 2. Weps. p 42. par 2. one of the Lu­minaries of Anatomy, observed; and after him Vieussenius, which are by Wepfer mistakenly taken for Arteries, who nevertheless, for ought I know, [Page 42]may be in the right, in assigning the overcloseness of the Pores of the Cra­nium (by what Accident soever hap­pening) thro' which the refluent Blood is transmitted to the Sinus, for a frequent cause of inveterate ob­stinate Headachs.

The fourth, FIG. 4. C. which from its situa­tion may not improperly be called the Internal Sinus, comes from the under part of the falcated Process, at that point where it becomes con­tinuous to the second Process of the Dura Mater, Ibid. II. and a large double Vein belonging to the Plexus Choroeides, together with the fifth Sinus, Ibid. K. (when there is one) enters it at an Interstice made between the end of the Corpus Callosum, the Nates, Testes and Cere­bellum, from whence having first pas­sed over the Cerebellum, it at last ar­rives with the other three at that place of union, which from its Author hath ever since retain'd the Name of Tor­cular Herophili. Ibid g.

The four others of Falloppius and Vidus Vidius, or Vieussenius, by this last called Superiores and Inferiores, the ^dd first two of which being longer and narrower, are call'd Superiores, are on the Basis of the Brain FIG. 2. dd., arise, [Page 43]according to him, from the Recepta­cula Sellae Aequinae, by the same Au­thor so named, (hereafter to be descri­bed, though more truly, from the ^ee circular Sinus, Ibid. EE as I hope in its place to make appear, running down from thence upon the internal Process of the Os Petrosum, and terminating in the Sinus Laterales, where they be­gin to be declive and λ tortuous in their passage to the internal Jugular. Ibid. λ.

The other two, called ^ee Inferiores, Ibid. ee. which are much shorter and wider than the others, descend from the same place as the former, between the Os Petrosum and Occipitale, down to the aforesaid eighth hole of the Cranium, where the Jugulars come up into the Brain, and end there.

Another I discover'd by having first injected the Veins with Wax run­ning round the Pituitary Gland on its upper side forwardly within a du­plicature of the Dura Mater, back­wardly between the Dura Mater and Pia Mater, there somewhat loosely stretched over the subjacent Gland it self, and laterally in a sort of a Canal made up of the Dura Mater above, and the carotid Artery on each out­side of the Gland, which by being [Page 44]tasten'd to the Dura Mater above, and below at the Basis of the Skull too, leaves only a little Interstice be­twixt it self and the Gland, thereby constituting a Cavity communicating with the two foremention'd forward and backward ones, from whence the abovemention'd four small Sinus's do descend, by a visible continuity, on each side from a little beneath the hinder Process of the Sella Turcica: FIG. 2. EE and this from its Figure may not un­fitly be called the Circular Sinus.

Vieussnius, it may be, saw some part of this Sinus where the other four small ones enter it, which is at the hindermost part of his Receptacula Sellae Equinae lateribus adjacentia, so called, and from thence thought those Receptacles to communicate with and to be capable of performing the office he assigns them, ( viz.) of bringing back Blood from the nou­rishment of the subjacent Bone call'd Cuneiforme, together with the Water separated from the Pituitary Gland, into these four inferiour Sinus's.

Now, as concerning these Recepta­cles of his, 'tis certain that they are not any where existent in Human Brains, (according to the description [Page 45]he gives of them in the place here noted) seeing both the third, fourth, Pag. 16. two foremost Branches of the fifth, as well as its third hindermost one, together with the sixth pair of Nerves, do not only run out of the Brain en­closed in so many distinct little Cap­sula's or Coverings made of the Dura Mater, during their passage through that part of the Basis of the Cranium by him call'd Receptacula, &c. but even the whole Dura Mater, together with its Membranous Productions constituting the aforesaid Coverings of those Nerves, in that place sticks close to the Basis of the subjacent Bone, (viz.) the External Process of the Os Cuneiforme, on its under side, and to the Carotid Artery (which also both above and below (as was before noted) by its borrow'd coat sticks close to the Dura Mater,) on that side towards the aforesaid Gland, leaving no room at all for either Blood or Serum to be contain'd there, as he would have it; tho' in the same place which he describes for his Receptacles I have in several injected Bodies observ'd two very fair and large Veins, one coming into the Cranium at the second Foramen from [Page 46]the Orbit of the Eye, (and possibly may be a Reductory Vessel to that part) and so climbs up on the side of the lateral Process of the Wedglike Bone, almost up to the Circular Sinus; the other at the fifth Foramen, which climbs up upon the same Bone till it meet and joyns with the other, from whence they make one short Branch, which enters the Circular Sinus very near the place where the two other inferiour ones on each side descend down from it; which if they should chance to be cut by accident in any enquiry made into that part, might cause an appearance of Blood, and thereby become an occasion of the aforesaid erroneous Hypothesis.

Neither is it possible (granting there were any such Receptacles as he mentions) they should serve to the end he assigns, Vituss. p. 55 seeing the Glandu­la Pituitaria is on all sides enclosed by both the Dura and Pia Mater; which first (notwithstanding what he says to the contrary) is on all sides of this Gland of a very strong and equal thickness; yea, in that very part where (as hath been before ta­ken notice of) there is a kind of a Chase made by a certain duplicature [Page 47]of the Dura Mater, constituting the foremost part of the Circular Sinus.

And if this also was granted, yet would the manner he describes of the Serum or Water getting into these Receptacles (which is by transcola­tion) render his Supposition very un­probable, seeing 'tis by no means conformable to the Custom of Na­ture in all other parts of the Body that Arteries should depose a Serum, or any thing else but Blood, (except what goes for Nourishment to the Part it self) in any Part, without be­ing furnish'd either with its Excreto­ry or Secretory Ductus, neither of which was ever pretended to have been found here.

And as a thorow confirmation of all this, said in opposition to the afore­said Hypothesis, I shall only add this, and conclude, that in several Injecti­ons made use of in order to find out the use of Parts, I never found one drop of the tinged Liquors on that side of the Carotid Artery, where he hath made the situation of these Re­ceptacles.

The use of this Circular Sinus is in common with the rest to reduce Blood returning from all the adjacent parts, as the Pituitary Gland, the [Page 48]Wedglike Bone also, and it may be from the Rete Mirabile, which in Brutes is very large, and therefore seems to require the Service of this Sinus, either mediately or imme­diately, for reducing a share of its Blood, seeing the Glandula Pituitaria appears no where furnish'd with Veins terminating any where else sufficient to carry off the refluent Blood from this Plexus, notwithstanding Vieusse­nius saith on the contrary it hath no Veins, and therefore is forc'd to have recourse to those small Branches of Veins which accompany the Bran­ches sent out by the carotid Artery, before it perforate the Dura Mater, with the Optick Nerves, or those which go to the Gangliforme Plexus of the fifth Nerve, or those coming out of the Wedglike Bone, for redu­ctory Vessels to this Part; but with what probability I know not.

CHAP. VI. Of the Motion of the Brain and Sinus's.

TO these Sinus's, especially the Longitudinalis, and by way of consequence to the Lateralis also, most if not all the Ancients, as well as Moderns too, particularly Willis and Vieussenius, Vitussen. p. 14. par. 3. have unanimously ascrib'd Pulsation, after the manner of Arteries, by reason of some Arteries (as they thought) from the Dura Ma­ter terminating in them: of the truth whereof being somewhat doubtful, I resolv'd to make use of such an Ex­periment as might remove all future Scruples, and most satisfactorily put an end to the Controversie; which was as follows.

I took off the upper part of the Skull of a Dog alive, by which means the Dura Mater with its third Lon­gitudinal Sinus lay bare to the Eye and Touch, to neither of which Senses, at first, either any beating of [Page 50]the Membrane in general, or of the Sinus, was the least discernable. After some pause, by chance the Si­nus it self, which I design'd to have open'd with a Lancet, being touch'd with a cauterizing Iron (which in making the Experiment there was occasion to make use of) pour'd out the Blood very violently, and at first without any very remarkable pulsa­tion, but alter some time discernable enough, both as to the Blood and Membrane too.

I cut this Sinus through almost the length of it, to see whether any Ar­teries (whereof many, according to Vieussenius, which was also long afore affirm'd, and that upon Experience too, by the learned Wepfer, did ter­minate in it, and so occasion its beat­ing, Wepf. p 116 par. 1.) would discover themselves by throwing out their salient Blood, but no such Sign appear'd.

After all which 'tis manifest the Sinus's themselves have no pulsation, other than what is communicated to them from the subjacent Brain, which contrary to what Bourdon affirms, hath an evident pulsation through the multitude of Arteries dispersed thro' Bourd. p. 196. par. 2. [Page 51]it so forcible as to create a sensible Systole and Diastole in its outward coverings.

'Tis worth noting, that while the Blood-vessels are all full, so as to keep the Dura Mater upon its full stretch, the pulsation is not vi sible at all, or at least very faintly; but after a de­pletion of the Vessels, so, as that grows somewhat more lax, the beating be­comes very visible, equally in the Sinus and Membrane too.

After having made this Experiment I found one Author of the same opi­nion, and that is Falloppius, who in vindication of Galen against Vesalius, his Contemporary, says, all I have said upon the foregoing Experiment, and all the great Vesalius was able to answer in his own vindication in his ingenious Book call'd Anatomicam Gabr. Falloppi Observat. Examen, falls very short of its aim.

As to the Transverse Ligaments which are in some places Fig. 4. r. round, cordal, and in others Ibid. x. broad or membranous, in the Longitudinal Si­nus chiefly, both serving for Strength and (in concurrence with the cruci­form ligamentous Fibres, taken no­tice [Page 52]of by Vieussenius, on the under and outside of this Sinus, from whence the Fibres belonging to the falcated Process aforemention'd seem to have their original,) Elasticity to this part for its more vigorous reduction of the Blood passing through it, together with its blind Cavities or Diverticu­lums serving to moderate the over-swift or violent motion of the Blood; seeing I find them so exactly describ'd by Vieussenius, to whom the Reader may have recourse, I think their de­scription need take up no room here.

But as to the manner of the Veins entring this Sinus, I find it far diffe­rent from that which is describ'd by Lower first, Low. fig. 4. h h. Vituss. tab. 2 D D, &c. and afterwards by Vieus­senius, both whom make them enter with their Orifices from behind for­wards, (two or three only excepted by Vieussenius) and that for some other useful purposes than what have hitherto been taken notice of.

And this is as follows, Fig. 4. dd, &c. (viz.) About one half of them (tho' intermixedly) (but all, after having first upon their ari­val at the Sinus insinuated themselves for some space alter the manner of [Page 53]the Pancreatick Duct or Ureters first taken notice of by Lower, Ib. dd, &c. betwixt the Duplicature of the Dura Mater) from behind forwards, the other half from before backwards, as in the Figure.

Now, by this contrivance 'tis plain, that first of all there are made two contrary Torrents in one and the same Channel, by which means the refluent Blood, made poor by the vast quantity of its richest parts drawn off as it were into Animal Spirits, thro' a collision of Parts, which by this contrivance must needs fall out, is preserv'd in its due mixture, which when at any time lost through the languishing of its intestine motion or elasticity, retards even its circular or progressive motion, which when it happens but in some degree, is the cause of many Distempers; and when altogether, of Death it self.

In the next place the circulation is at all times not only somewhat re­tarded, and the Blood hinder'd, (toge­ther with the help of the bony Cell at which the internal Jugular Veins enter the Sinus's) especially in an erect posture, from descending with that rapidness and weight it would [Page 54]otherwise have done upon the descen­ding Cava to the Heart; but also much more so retarded in a supine position of the Head, a posture most natural and ordinary for Mankind to take their rest in, through which con­trivance, in concurrence with that of the Lateral Sinus's, (whose structure is such, that in the aforesaid posture the Blood is forced to climb upwards before it can arrive at the place of its descent into the Jugular Vein) there is made a more plentiful gene­ration of Animal Spirits, one chief Cause of the great refreshment and vigorous disposition of the whole Body we find after Sleeping.

As to the other manner of the Veins entring this Sinus, ( viz. from before backwards) it from thence happens, that in a prone Position of the Brain, a posture not uncommon amongst Men, the Blood is help'd forward in its circulation through the Sinus; the truth and design whereof are at once both evident and pointed at by Nature from the Structure of this part (and which therefore shews the great usefulness of Comparative Ana­tomy) in Brutes, who by reason of [Page 55]such a Position, which the necessity of Feeding almost always keeps them in, have always such a disposition of this Part, to assist the Blood in its heavy circulation.

The design of Nature in making these Channels so wide on a sudden, in respect to the Branches of Veins lately treated of terminating in them, seems to correspond with the con­formation of the Parts just now trea­ted of, and with that it had in ma­king the Ramifications of Arteries afore taken notice of so large and unproportionable to the Trunks from which they spring, which is a flower than ordinary circulation of Blood through the Brain, in order to make a still more copious production of the Animal Spirits so called. Which pro­fitable Design and End of Nature had nevertheless been attended with a very great Inconvenience, (viz.) an extravasation of too much Serum, the usual effect or consequence of a slac­ken'd Circulation, had it not been for another provident Contrivance of Nature in the two Communicant-branches, betwixt the Carotid and Vertebral Arteries aforemention'd, [Page 56] p. 36. by the narrowness of whose Channel the influent Blood is in some measure represt in its motion, and an overcharging the Vessels with Blood prevented.

These Sinus's differ in structure one from another, the Longitudinal and Lateral ones having many trans­verse Ligaments which the other have not, and the Longitudinal having ma­ny small Cavities or blind Diverticu­lums, as aforesaid, which the Lateral have not; the use of them all being for strengthening and defending them from giving way to the violent ir­ruption of Blood into them, against which sometimes notwithstanding they are not able to defend them­selves; as I have seen in many Skulls ni which the Blood hath burst open the sides of the Sinus's and found its way between the Duplicature of it, so as even to have made a Fovea or Cavity in the Cranium it self, as was before noted, one of which I have now by me.

CHAP. VII. Of the Plexus Choroeides.

THIS Plexus is an aggregate Body made up of Arteries, Veins, Membrane, and Glands, double on each side, (which hath not before been taken notice of) and conse­quently having two Originals.

The first Original is from the fore­most Branch of the Communicant Artery, FIG. 1. ee. which running backward up betwixt the hinder Lobes of the Brain, (in which for some part of the way it is immerged, and to which it gives many large Branches) and the Medulla Oblongata at length arrives at the Lateral Ventricles, FIG. 5. ee. and makes one part of the Plexus on each side.

The second Original is from the hindermost Branch of that Commu­nicant Artery, FIG. 1. second ee. which running more backwardly, ascends betwixt the hin­der Limbs of the Brain and the Ce­rebellum, till it comes to the Isthmus, [Page 58]where communicating with the first Branch abovemention'd, they make a reticular broad Expansion, which co­vers both Nates, Testes, and Glandula Pinealis, FIG. 5. GG and constitutes the second or other part of the Plexus Cho­roeides.

The first Branch begins to divide it self into divers Network Fould­ings, interspersed with Glands some­what what before it enters the Ventricles, Ibid. 5. and continues such to its Extremity on each side, where they both under the Fornix wind cross the third Ven­tricle into a mutual inosculation.

The second begins to assume the same shape or contexture as soon as it begins to enter the Isthmus, conti­nuing such throughout its entire abovemention'd Expansion.

These two on each side are joined together by a twofold connexion, the first is by an Artery running un­der the Bombyces, intervening betwixt them, which could not be here inser­ted so as to come in view.

The second is by a production of the Pia Mater, which is extended all over these parts of the Lateral Ven­tricles, and the third Ventricle which [Page 59]lyes betwixt the first two parts of the Plexus forwardly, and down to the other two hinder parts of the Plexus backwardly under the Fornix and Septum Lucidum; so that whatsoever Water is transmitted out of these Ven­tricles, must slip down not only un­der the Fornix, but that Membra­nous Production it self; from which kind of structure and position of this Membrane may probably be under­stood how there might happen such an Hydrocephalus as the learned Tul­pius mentions, Tulp. lib. 1. cap. 24 in which there was found above two pounds of Water in one Ventricle, without any at all in the other: and such another as Wepfer mentions, Wepf. p. 69 where the Water causing the Hydrocephalus in an Hei­fer, was found contain'd in a Cystis, and that only in the left Ventricle too: for, supposing this membranous production of the Pia Mater to be double here, as it certainly is in all other places, 'tis not difficult to con­ceive, that the Water which is ex­travasated must needs insinuate it self betwixt the two Lamina's, till by a continual encrease it extends them into the shape of a large Bladder, [Page 60]such a one as the latter found there and drew out with his Fingers; and that which seems to put out of all Controversie that it was so, is, that in those places, both above towards the Corpus Callosum, and below on the Basis of the Ventricle, he found some sort of Asperities as though the Blad­der fill'd with Water had been cove­red with some small Protuberances not much unlike to White Poppy­seed, in those places where it was contiguous to them; which Protu­berances doubtless were the small Glands interspersed quite through this Plexus.

How this Distemper came to be on one side only, though sometimes it is on both, as you may see in ano­ther place of the aforesaid Tulpius, may likely enough be from an Ad­nascency of both the Lamina's of this Membranous Production, Willis p. 10 col. 2. par. 1. in that place where the Septum Lucidum sinks down from the Fornix, occa­sion'd by some small sort of pressure of the superincumbent Brain. Be­sides these Veins, which are very truly describ'd by Willis, I have al­ways found two more meeting the [Page 61]foremost Extremities of this Plexus, from between the two first Lobes of the Brain, where it seems to end un­der the foremost part of the Corpora Striata, by which it is there fixed and as it were kept in its due situa­tion: and from these Branches are on each side sent forth many more little ones to the Corpora Striata, and se­veral other parts adjacent.

To this Plexus belong also Veins, which from the Extremities of that part of it in the Lateral Ventricles begin to come into two distinct pret­ty large Trunks, FIG. 5. hh. running down thro' the middle of the third Ventricle, as far as the fourth Sinus, and there re­ceiving some Branches from the other hinder part of the Plexus spread over the Isthmus, discharge the refluent Blood into that Sinus.

But besides this sort of Reductory Vessels, Ibid. qq. it hath also another, (viz.) Lymphaeducts, which I first discover'd in the Brain of a strangled Body, and shew'd to several then present, run­ning in different ramisications amongst the reticulated Vessels and Glands of this part: Which Observation being added to that of the great Anatomist [Page 62] Anthony Nuck, who in that curious Piece call'd Adenogrophia says, Nuc. p. 150. he saw one coming from the Glandula Pinealis, and that his Friend another Anatomist, whose Name he mentions not, (but I know it was one Bodivol, whom I had the Happiness to be very well acquainted withal, now dead) sent him word, he saw another not far from the aforesaid place; may be of sufficient authority to evince the real Existence of these Vessels hitherto so much enquir'd after, in the Brain as well as in other parts of the Body.

The Glands belonging to this Plexus are very many, but very small, and their Use, according to all the Moderns, especially Willis, Duncan, and Vieussenius, to carry off the re­dundant watery part of the Blood, but that without ever shewing by what rational contrivance of Structure it can be done, seeing none of them ascribe a Secretory Duct, which must always be in readiness when any unprofitable part is to be discharg'd.

Since therefore this part is found furnish'd with Lymphaeducts, 'twill be no hard matter to conceive the ge­nuine use of the Glands, which is, to [Page 63]separate a rich nutritious Juice from the influent Blood, and by the Lym­phaeducts to refund it to the refluent, after the loss of its noblest parts left behind in the Brain in its passage to the Heart again.

It may also, for ought I know, ac­cording to the Opinion of Willis, serve to warm its neighbouring parts the Internal Superficies of the Brain, which being purely medullary, hath not so plentiful a share of Blood-ves­sels dispersed through it as the rest, and consequently, to maintain an equality of warmth conducing so much to the conserving the Spirits in their due vigour and exercise, must borrow an additional supply from hence. It is situated upon the middle of the Thalami Nervorum Opticorum, all-along them length way, and, con­trary to what Willis says, is, by vertue of several Blood-vessels, join'd to that medullary part of the Brain so call'd, immediately lying under it.

CHAP. VIII. Of the Rete Mirabile.

NOtwithstanding the Opinions of the late Wepfer, Willis, and Vieussenius too, (which two last in­deed, tho' but now and then, are wil­ling to allow it an existence only in Men, (who nevertheless, if the Suppo­sition of Willis be true, viz. That such cannot but be Fools) had better be without it, Willis p. 2 [...]. col. 2.) together with almost all the Ancients, as Vesalius, Columbus, &c. to the contrary, I have never found this Rete wanting, or with any diffi­culty discoverable in Men, springing from and lying on the inside of each Carotid Artery, in that place of the Circular Sinus chiefly which looks in­to the four abovemention'd inferiour and superiour Sinus's in the Basis of the Brain, and in some measure also the whole length of the Sella Turcica, on each side, between the Gland and the Carotid Artery.

And that it is so small in them with respect to what it is in Brutes of several kinds, is no way surprizing, when consideration is had to the Use and Service of it in those Creatures, [Page 65]who, by reason of their prone Posi­tion, would otherwise be in danger of having their Brains deluged as it were with an over-great quantity of the Influent Blood, and of a Rupture of the Vessels, by its violent ingress, and this Danger so much the more threatned by how much the same Cause which brings it into the Brain with that force is equally as great and effectual to hinder its proportionable return; for the relief of which In­conveniency Nature hath contriv'd a means of its more easie and safe de­scent into the Brain, by turning that one large Stream of Blood, (which through its being penn'd in one Channel, becomes so rapid) into ma­ny more, (by which means the Ca­rotid Trunk above the Dura Mater in those Creatures is very small to what it is beneath, whereas that Ar­tery in Men, &c. hath the same big­ness on both sides that Membrane,) and they not only reticulated and contorted for the more slow and la­borious (which Contrivance the Ancients thought was only for a more exact preparation of the Blood for Animal Spirits) descent of the Blood, but also many of them by their insertion into the Glandula Pi­tuitaria [Page 66]attended with small Veins issuing thence, to take off some part of the burden too.

This last contrivance of Nature methinks may be sufficient to render that Controversie of Vieussenius with Willis (which, before them, Vieuss. p. 16 pat. 2. was be­wixt Waleus and Rolfincius) the two latter on each side denying this Rete to have any Veins, very needless; feeing that if the Pituitary Gland have any, which I am confident it hath, (notwithstanding the positive Asser­tion of Diemerbroeke, Diemerbr. p. 364. par. 3. in order to serve his own most unprobable Hypothesis, to the contrary) as having seen them plain injected with Wax; then this part of the Blood in some of the Bran­ches of the said Rete, which are plainly inserted into the Gland, is equally capable of being reduced by those Veins without any necessi­ty of having recourse to those re­mote Branches Vieussenius hath been forced to seek for, Vieuss. p 45 par. 2. as if it had had them of its own.

And that to the aforesaid Position of different Creatures ought chiefly to be ascrib'd the variety of Magni­tude of this Rete in several of them, its size in Dogs seems highly to evince; [Page 67]in which, by reason of their Hori­zontal Position, being neither so prone as several Brutes who seed on Grass, nor so erect as Man, that Rete is found smaller than in the first, and larger than in the last.

Another Use it hath been thought to have, is, to carry off a considera­ble quantity of a dull watery part of the Blood, in order to the producti­on of the finer Animal Spirits; and this it is thought to effect by means and help of the Pituitary Gland, be­twixt which and it self there is con­stantly observ'd a greater affinity, the one being either greater or lesser in proportion as the other is so, and be­twixt, which there are in all Crea­tures, but more remarkably in those where they are both large, a distri­bution of several Branches coming from the aforesaid Rete. And this is look'd upon by Vieussenius so consi­derable an office of the Glandula Pi­tuitaria, that in those Creatures where it is but small, as in Men, Horses, Dogs, &c. he hath sub­stituted many, Vieus. p. 102 par. 3. but particularly two Cavities, for that use in the Wedglike Bone, just under the Sella Turcica, in which he supposes that [Page 68]part of the aforesaid Serum, which by the smallness of the Rete can­not be return'd that way, is re­mitted by several little Arteries slipt off from the Carotid, whilst under the Sella Turcica, terminating in the two abovenamed Cavities, there either deposing a part of the Serum to be carried off by a strange way he there mentions, (viz.) by two holes, into the Nostrils, and thence into the Fauces; or else by certain Veins meeting them in that place, as their proper Reductory Vessels, Vieuss. p. 9. par. 2. to the Heart.

Now, as to this office of the Glan­dula Pituitaria, I cannot easily be perswaded it is either design'd for, or capable of it, till such time the Abet­tors of this Opinion can be able to show me it furnish'd with an Excre­tory Duct for this purpose.

And if they offer, that the Veins are such, I reply, That (besides its being very unprobable that so vast a quantity of Blood as continually is brought by the Carotid Arteries to the Brain, should be able to get rid of any considerable quantity of its Serosity, by so small a part as the Glandula Pituitaria is;) 'tis not the [Page 69]usual way of Nature to part with any Share of its Juices out of its Vessels, when so unactive and unpro­sitable as this is, and immediately to receive it in again, seeing it is pro­vided of Emunctories enough to con­vey it away by.

Moreover, granting (which by no reasonable means is to be granted) it were so as they would have it, yet nevertheless, in conformity to Na­ture's proceedings in all such-like case, there ought to be an interme­diate passage by way of a Secretory Duct, which none hath been able hitherto to discover.

And so far as Vieussenius seems to be of this opinion, Vieus. p. 102 par. 3. which in one place he plainly is, making it of so gross and viscid a nature, as is only sit to be discharg'd at the Emunctory of the Nose; the same Reply is satisfa­ctory: But when by way of flat con­tradiction to himself he comes to make the same gross Humour a per­fect fine Lympha, the Answer is then, Vieuss. p. 54. par. 1. That there is no need of parting with it beforehand, seeing we find that Liquor only separated by the Lymphaeducts of the Brain afterwards.

Seeing therefore there is such an affinity as before mention'd, between the Rete Mirabile and Glandula Pitui­taria, and taking it for granted, that the office of the Glandula Pituitaria is not what it hath generally hither­to been believ'd, to the end we may attain a more exact knowledge of what it really is; it seemeth not al­together immethodical to take that part into consideration in the next place, together with the Infundibu­lum, which last hath not only as near a relation to the Gland as the Gland hath to the Rete, but such a close communication with it, that it seems in a manner almost impossible to treat of one independently on the other.

CHAP. IX. Of the Glandula Pituitaria, and Infundibulum.

THIS Gland is seated in and fills up in a manner all that space contain'd within the Sella Tur­cica (Vessels only excepted).

'Tis cover'd on all sides with the Pia and Dura Mater, excepting that part on its upper Superficies, in which there is a little round hole, by which the In­fundibulum descends slopingly into it, being at its entrance inviron'd with a Production of the Pia Mater, for its more firm connexion with that part, as was before noted.

But as to the Dura Mater, it en­compasses it after a far different man­ner than what Vieussenius hath de­scrib'd, Vieuss. p. 51 par. 5. not suspending it in Man as it doth in Brutes, so as to hinder it from touching the bottom of the Sel­la, and that forasmuch as there is not the same reason for its so doing in one as there is in the other, for in [Page 72]Brutes the Rete Mirabile is not only situate on each side this Gland, but: runs quite under its hinder part, by which one side of the Rete commu­nicates with the other, a Disposition of this Part which Vieussenius was al­together unacquainted with; whereas in Man, inasmuch as there is not that sort of Structure in the one ( i. e. the Rete) 'tis not nccessary it should be requir'd in the other.

However, in neither one nor the other is the Reason which Vieussenius gives for Nature's contrivance of this affair of any weight, seeing neither the Rete Mirabile, Vieuss. p. 50 par 1. much less the few small Veins belonging to the Bone beneath, could possibly any way be compressed by this Gland, though superincumbent, because it is so firmly knit to the Dura Mater, ly­ing above and upon it, which is sup­ported by the two foremost and hin­dermost Processes of the Sella Turcica, in such a manner as is sufficient to sustain and keep from pressing upon any subjacent part ten times a grea­ter weight than the Glandula Pitui­taria is.

Moreover, the Dura Mater is so far from suspending it from that [Page 73]Bone, that it is, together with the Gland, fixed to that very Bone it self.

The substance of this Gland is far differing from that of all the rest, which I have often upon this account particularly examin'd; in consistence indeed 'tis the same with most of the Conglobate kind, if not somewhat harder, but then being pressed or squeezed, it emits much more Water than any of them.

As to the Conglomerate sort, it hath not the least resemblance to any of them, and consequently cannot be suppos'd, as it hath hitherto been by all, to carry off any excrementitious or unprofitable pare of the Blood.

Now, if we consider this part, to­gether with the appended Infundibu­lum, we shall certainly find a confor­mation far different from any other part in the whole Body of Man, in­asmuch as that which this Gland receives by the Infundibulum, or which is the same, what this Infundibulum conveys to it, is not separated from the mass of Fluids by any visible Secretory Duct, which in its ordina­ry method Nature is observ'd con­stantly to make use of, whensoever [Page 74]it parts with any part of the Blood, whether excrementitious or reductitious, throughout the whole compages of the Body.

Nor hath the manner of Nature in transmitting a certain Liquor to the Gland been less abstruse in carrying it off from that part again, the re­ductory Vessels from the Gland be­ing equally conceal'd, as the addu­ctory to the Infundibulum; that way of Transudation, according to the invention of Vieussenius, being to the greatest degree improbable, as having no resemblance to the course of Na­ture throughout the whole Body.

Nay, even a possibility it self seems hardly allowable, if we take but no­tice of that part in Brutes in whom its Integuments are extraordinary dense, the Dura Mater, as he truly observes, investing it close on every side, (and which he perceiving, and consequently foreseeing what might from thence unanswerably be objected against him) was forced to make them much more than in Men; in which last indeed there is seemingly. some reason for its being so, Vieuss. p. 52 par. 2. inas­much as the Rete lies in a Duplica­ture as it were of the Dura Mater, on [Page 75]each side of the hindermost part of the Sella Turcica, as tho' one Lamina of it was spread upon the subjacent Bone, and the other over the Pitui­tary Gland, (a disposition contrary to that in Brutes, as hath already been taken notice of) but neverthe­less there is no necessity that it should be so divided in this place, nor doth the said Author ever offer a Reason for its being so, (which looks as though his Assertion was only a Guess) seeing this Membrane can send out new Productions as well double as single, as we find in its two eminent Processes before de­scrib'd, and Sinus's; agreeable to what it also therefore may and does do here, where the Integuments of this part appear plainly to be of too thick a consistence to admit of his imaginary way of transudation, which is manifest not only by sight and secti­on, but in that by the greatest force made use of in compressing and squee­zing it between ones Fingers, we find it impossible to force out the least appearance of Humidity through its aforesaid Inclosure or Integuments,

Being therefore very inquisitive after the true use of this part, and [Page 76]despairing of ever attaining to such a Knowledge without first knowing the exact Structure thereof, besides all other means commonly made use of in all Anatomical Enquiries, I made use of all sorts of Injections serviceable to such an end, as of tinged Li­quors, Wax, and Mercury, but all with little, if any, success according to my expectation, the Wax not pe­netrating its Texture at all, the tin­ged Liquors but very superficially, and the Mercury, (where my chief Hopes were) always by its weight (do what I could to the contrary) either breaking through the sides of the Infundibulum, where it leaves the Brain, or else falling down in greater Globuli than the extream narrow Passages were capable of ad­mitting. and by this means became altogether useless.

Being compelled therefore for the present to leave off a little while a further enquiry into the Structure of this part, by reason of the great mist it is involved in, and to gain a little more Light for our Gui­dance in searching after Truth, (which like many other things of greatest value lyes deep, and is [Page 77]with great difficulty accessible) it may not be amiss to see what Assistance can be had, by making diligent Scrutiny into the Structure of its Appendix the Infundibu­lum.

The Infun­dibulum.This is a thin medullary Duct, covered with the Pia Mater, de­scending from the internal Concave Superficies of the Brain, to which, by reason of its wideness towards one end, and narrowness towards the other, in resemblance to a Tunnel, as well as by reason also of the parity of their Uses, the Ancients gave the Name of Infundibulum.

In Man it is closely inverted with the Pia Mater at its very entrance into the Gland, and from that place hath not any manifest Cavity I could discover by blast or style, but is altogether of a medullary substance, contrary to what it is in Sheep or Calves, in which last Creature, where the Parts are lar­ger, by inserting a Blow-pipe into that part of the Infundibulum, next to the Gland, I have seen its further Tract or Passage on the upper part thereof a little puffed up, and a con­siderable [Page 78]quantity of Water regurgi­tate, as though it had lain contain'd either in some Pipes or Porulous Sub­stance of that Gland.

This Difference is not take no­tice of by Vieussenius, and therefore what he says of this part seems chie­fly in this respect, if not altogether, applicable to the Structure it hath in Men.

Those two Divisions or Ramifica­tions of this part the said Author men­tions, Vieussen. p. 49. par. 3. one forwardly, and the other backwardly, in Sheep, Calves, &c. I have always found correspondent to the Descriptions he there gives of them; but whether the first be protended so, and terminate after the manner he there describes I somewhat scruple, seeing I have al­ways observ'd the Extremity of that part in Brutes, towards the foremost part of the Gland, sinking as it were into the very Substance thereof, and afterwards becoming presently altogether imperceptible, and in Man the termination thereof just after the same manner, save only that in the last it happen forthwith upon its approach to the Gland, [Page 79]without being protended either back­wardly or forwardly.

The Use of this part is certainly to convey some sort of Humidity from that great concamerated Cavi­ty within the Brain, resulting from its inward complication of parts, to the Pituitary Gland, and the office of it is to receive and carry off this transmitted Humidity; but as to how either this Humidity is collected in the aforesaid Cavity, or how, when convey'd into the Gland, it is carried off, we are still as much in the dark as ever.

I know very well there is nothing more easie with the Visionary Philo­sophers than such a Knack as this; and now I think on't, the great Wil­lis makes nothing of turning a Vein into a Lymphoeduct in the Glandula Pinealis and Plexus Choroeides, Will. p. 46. no less than which does also the accu­rate Vieussenius, Vieus. p. 110 par. 3. in the Plexus belong­ing to the fourth Ventricle; but how consonant this is to the rational stru­cture or mechanism of parts, neither the one or the other have been so kind as to explain.

Now, as to the Plexus and Glands before mention'd, 'tis evident by what hath been already discover'd and ac­cordingly given an account of in the preceding Pages, they are furnish'd with Lymphoeducts, as proper redu­ctory Vessels; so that so far the Pro­phecy is vanish'd.

But as to the remaining Gland, I am not so fond of guessing to say it hath any, and consequently all I can say is, that as I look upon the In­fundibulum to be no more than a large Lymphoeduct variously ra­mified through the Glandula Pitui­taria, discharging its Liquor by those many small Branches into the Veins dispersed through that part to be reduced after the manner 'tis in all other Secretory Glands back to the Blood gain.

And that which seems most to fa­vour this Conjecture, is the extraor­dinary humidity of this Gland, especially in Brutes, above the rest of the whole Body, as serving not only to export what Lympha is separated from several Arteries dispersed thro' it, but that also which it is charged with from the Brain it self.

And to this twofold manner or double office of Secretion is owing the two distinct Substances it seems to consist of, the one being accom­modated to that part of the Lympha coming from the Brain, and is there­fore whitish, the other to that sepa­rated immediately out of the Blood, and is therefore reddish.

Lastly, As to the manner how the Lympha passes down thro' the Infundi­bulum passes down thro' the Infundi­bulum from the Brain to the Glandula Pituitaria, I look upon it to be in the form of condensed Vapours arising from the Arteries of the Plexus Cho­roeides, emitted thence for the keep­ing moist and in good order that in­ward Production of the Pia Mater, spread all over its Parietes, which being a membranous dry part of it self, might otherwise become inju­rious to that fine medullary part lying under and being contiguous to it; in which there is a continual mo­tion of Animal Spirits, whose Tracts, and consequently they themselves, through any the least intemperance of this Membrane, would be in great danger of either some obstruction or disorder.

And that this Lympha is only the result of the aforesaid Vapours, I am the more readily enclin'd to believe, because I never saw Water in that part of any sound Brain, nor unsound neither, where the Plexus Choroeides was firm; and there was no reasona­ble ground, by the extravasation of Serum in some other remote parts of the Brain, to believe it had its rise from thence.

CHAP. X. Of the Glandula Pinealis.

THE Gland call'd Pinealis, from its Figure, is about the bigness of an ordinary Pea, prefix'd to the two Prominencies call'd Nates, here­after to be describ'd, at the end of the third Ventricle, immediately un­der the broad and hinder part of the Fornix, (with which nevertheless it hath no connexion, Vieuss. p. 71. as Vieussenius saith it hath) and over that part of the Rima in the third Ventricle call'd Anus.

'Tis joyn'd to the Nates by seve­ral Fibrous Roots, and becomes a sup­port to that part of the Plexus Cho­roeides there situate.

In an hydropical Brain of a stru­mous Boy, I have seen it swelled to a size of three times its ordinary mag­nitude, and by reason of the abun­dance of stagnate gelatinous Lympha contain'd in it, perfectly transparent.

Hence it most plainly appears that this part is a meer Gland, and, by what was said before conformable to what hath been observ'd in this hy­dropick Brain, of the Conglobate or Lymphatick kind, and by consequence a very unfit part to be made a Re­ceptacle of Animal Spirits, Vieus. p. 71. as Vieusse­nius makes it, and much more a place of residence for the Soul, according to Des Chartes.

'Tis true, there are two fair me­dullary Tracts arising seemingly from the two Roots of the Fornix, stretching length-way upon the Tha­lami Nervorum Opticorum, as far back as this Gland, (by Vieussenius called as this Gland, Vieuss. p. 6 [...] par. 3. (by Vieussenius called Tractatus Medullaris Nervorum opti­corum Thalamis interjectus, as though it was only one, and accordingly is so delineated by him, Tab. 7. GG, but indeed is two, one on each side) about which place they turn in, and by a transverse bending kind of a Process (by the same Author call'd Tractus medullaris natibus antepositus) unite, as he hath exactly observ'd: Willis, p. 9. col. 1. par. 1. And this, doubtless, gave occasion to the Error of Des Chartes, as Willis tru­ly thought, (whose sublime and most [Page 85]deservedly-admir'd Philosophy had doubtless been much more useful, had he convers'd more with Dissecti­ons, and less with Invisibility) and Vieussenius too, Mural. p. 508. Will. p. 10. col 1. par. 3 (with whom in the same Mistake doth agree Mu­raltus and Willis) for upon a more heedful inspection (as was most evident in the Brain afore­mention'd) it will be found that no part of the Process aforesaid, however near it comes to this Gland, does in any wise become con­tinuous to it.

Dr. Wharton also stumbled upon these medullary Tracts, Whart. p. 141. placing them amongst the Nerves them­selves, and ascribes the same un­reasonable use to them as he does to the Nerves in many other Parts of the body, (viz.) of separating a superfluous Humour from the Cruca Medulla Oblongata, or Tha­lami Nervorum Opticorum, (being the same Part, and only on the other side or upper part of the Brain, under another denomination) which he supposes to be the Commune Sensorium.

It hath Arteries and Veins in common with other Glands, the Veins ending in the fourth or in­ward Sinus; as may the Lym­phaeducts too, when they are con­spicuous.

CHAP. XI. Of the Brain in general.

THAT part of this Treatise relating to the Vessels, being dispatch'd, I shall in the next place proceed to an account of the Brain it self, under which term are gene­rally comprehended the Cerebrum and Cerebellum, and Medulla Oblon­gata, which Parts being in many respects so different one from ano­ther, may justly challenge a distinct and orderly description.

The Brain then, in the first place, as distinct from the other two, is that large and almost spherical Body which comes first to sight in the old way of Dissection, filling the grea­test part of all that space contain'd in the Cranium, consisting of two different Substances (first taken no­tice of by Archangelus Piccolominius) both in Colour, Consistence, Piccolom. p. 252. and Office, the one being more com­pact, [Page 88]white, medullary, or fibrous, the other softer, greyish, and glan­dulous.

The utmost Malpighius (by ver­tue of his Microscopes) could do, Malp. De Cereb. Cort. p. 78, 81. par. 3. was to discover the Cortical part to consist of Glands of an oval depres­sed Figure, and in his Opinion, of the Conglomerate kind, (but that how properly, as also his calling the Nerves their Excretory Ducts, I leave to the Judgment of others) and the Medullary part to consist of various Fibres immerged in and having their original from the aforesaid Glands, deriving from them a certain Liquor call'd Nervous Juice, concerning the Existence of which, in the usual sence 'tis taken in, as a fluid body, contain'd and running continually in the Channel of the Nerves, as Water in Wooden or Leaden Pipes, for either Nutrition or Censation, is a thing somewhat improbable, it be­ing not only possible, but very easie to resolve those two Phoenomena's, the first from the Blood, and the other from the Natural Tenseness of Sensible Parts maintain'd by the sup­ply of a proper Liquor from the [Page 89]Blood, both in their Originals and continued or elongated Productions; inasmuch as it doth as certainly cir­culate in them as in any other parts of the Body. And as to the manner how this is done, it will appear very plain and intelligible, after the in­nate Structure of the Part hath been more accurately enquired into.

The Curious Lewenhoeck made a far deeper scrutiny into these two Parts, Lawenh. de Struct. Cereb. p. 37. being very probably assisted by better Glasses, and from what occurr'd to his view, called the cor­tical part a pellucid Vitrious Oily Substance, (the seeming oiliness of which Substance I attribute only to the stagnating of the pure Liquor, growing cold after death of the Creature,) from such a close and regular Position of the Globuli swim­ming therein, as allows the Rays of Light to pass them without refra­ction, contrary to what they do in the other or medullary part of the Brain, in which they are so dispos'd that the Light cannot pass them in right lines, and consequently being a little distorted, makes them appear [Page 90]white, notwithstanding Malpighius on the contrary neither allows the Parts of the Brain to be diaphanous, Malpig. de Cereb. p. [...]. nor the Animal Spirits to be any thing a-kin to Light.

'Tis true, even by his own con­fession, that his most nice and dili­gent Inspections could not free him from many Scruples about what he saw; yet some things to our pur­pose were plain enough, as Reticu­lar Bodies of a red colour, which being larger in the Cortical Parts than Medullary, helps to give it that greyish or subrunneous colour, as he calls it.

Nextly, a transparent Vitrous­colour'd Substance contain'd in most minute Vessels; whence 'tis plain there are two sorts of Liquors in this Cortical Part, one of a red co­lour, or Blood, contain'd in larger Vessels, whose Globuli, which give it its redness, either by reason of their size or figure, cannot enter those small Vessels which with the Fluid contained in them constitute this transparent, cineritious, or cortical part of the Brain.

The other a transparent Liquor, contained in most minute Vessels, as aforemention'd; from whence I am induced to believe this Cortical part to be only an Aggregate of different Vessels, (as also I do of all the rest of the Parts of the Body) containing different sorts of Fluids.

Of these Vessels some contain a more compound Liquor, commonly call'd Blood, which whilst in that state, by reason of the Globuli swimming on it, looks red, and by reason of a tubulous Pore of a pro­per size and figure so continued to the Vessel we call a Vein, that it undergoes a continual quick circu­lation.

Another sort of Vessels there is which receive and contain a more simple fluid body, of a thin tran­sparent nature, which when in some parts of the Body, gives the name of Lymphaeducts to the Vessels that it runs in; but when in these Ves­sels, which are discover'd to make up the great Substance of the Brain, whether Cortical or Medullary, may be allow'd the name of Fluidum Ani­male.

And this last sort of Vessels I look upon to be either a certain Protension of an Artery, by its smallness render'd capable of hold­ing such a sort of Liquor only as the last spoken of, or else such a tubulous production of the Artery as by its Orifice of Pore answers to the figure and size of the Fluid it is by Nature intended to receive.

Upon the same exact Enquiry made by a Microscope, the medul­lary part of the Brain appears to be of the very same constitutive parts, ranged only after a somewhat different manner, which makes this part appear more white, as was before observ'd. But over-and-above (if it may be allowable to make a Conjecture) I am enclin'd to think the Whiteness of this part may be owing in some, if not the greatest part, to such a narrowness of the Vessels discover'd here, containing the pellucid Substance aforemention'd as will not entertain any Fluid what­soever, without its being first re­duc'd into very minute Particles, or Septometry so called: Which last Vessels I therefore suppose to be [Page 93]only yet more Capillary Producti­ons of the aforesaid Cortical Ves­sels, as they are of the red or Blood-vessels indu'd with such a Pore as fits them only for the re­ception of a most subtile, fine, soft Liquor, which I esteem the true Medullary and Nervous Juice, which being contained in its proper Cap­sula, and many of them collected into one Fasciculus, at its egress out of the Brain, being there wrapped up in more thick and strong Cove­rings made of the two outward Membranes of the Brain, do consti­tute that part we call a Nerve, which having all its Integuments or Membranous Inclosures always kept turvid and tense by its contain'd Fluid, after a slow and leisurely manner continually dispensed from the Fountain, and by its growing more taper towards the place of its termination, by which means it ac­quires a greater streightness or nar­rowness of its Pores ordinarily call'd Fibrillae, it so falls out that all inward Impressions, upon all occasions, are the more easily and speedily trans­mitted through it.

The very same notion also con­cerning Nutrition (which in the truest sence is only an apposition of Parts nourishing to Parts pre-existent to be nourished) in the rest of the Parts of the Body, I have thought reasonable to entertain ever since, by assistance of the Microscope I have plainly discern'd the Veins to be only continuations of Arteries, and the Blood to run in the same Channel variously modified, without the least suspicion of Extravasation, (viz.) a continual transmission of Nutritive Juice out of the Pores of Arteries, after many windings like Tindrils of Vines ( Analogus to which the red Reticular Bodies of Lewen­hoeck seem to be in the Brain,) grown very capillary into certain Tubuli's or Pores of a corresponding bigness and figure, making up the whole fleshy part of the Body, whose Substance, when 'tis freed by wash­ing or injection of Water, we see to consist only of large and small Blood-vessels and Fibres; which last, whether Nervous or Membranous, or such as relate to Muscular Mo­tion, commonly called Carnous, I [Page 95]suppose to be full of minute distinct Vessels for the communicating and receiving their proper Liquors or Fluids after the manner already ex­press'd, which as contain'd in the said Tubuli or Pores, whilst they re­tain their Natural Constitution and Proportion, I presume it is which keeps the Habit of the Body plump and vigorous, the more thin and languid being perpetually carried back by the Lymphatick Vessels, and a great part wholly extermina­ted by meer simple Transpiration; which I adventure to think is not only superficial from the Sudorifick Glands in the Skin, but also through the whole Substance of inward parts, through small Canaliculi's or Mean­tus's in even the Viscera themselves; by which, not unlikely, we may guess at the Meaning of Hippocrates, when he said, All things were conspi­rable and transpirable.

The minuteness of Vessels is that which hath so embroil'd the Thoughts of Naturalists upon this Subject, and set Realities so remote from the Un­derstanding, otherwise 'tis no Para­dox to affirm the Existence of Vasa [Page 96]Vasorum almost to Infinitum, some containing Liquids in a continual more nimble circulation, others in a gentle protrusion only: Which will appear altogether unsurprizing, if it be consider'd that the afore­mention'd Ingenious Author hath computed, that even the 64th part of a Miriad (i. e.) of a Ten hundred thousandth part of any Substance but as big as a small grain of Sand, Leweth. p. 46. cannot, especially if of a rigid or in­flexible nature, enter those little Ves­sels, which are seen in a retiform manner distributed amongst, and fix­ed to the aforesaid pellucid Globules, which swimming in those little Ves­sels, are discover'd to make up both the Cortical and Medullary part of the Brain. As also further, that even the tender Coats of the smallest of those Vessels which contain the afore­said most minute Globular Fluid Bo­dies, Lewe [...] are also full of yet far more minute Vessels than they themselves are.

Nay, I am so far from being sur­priz'd at this kind of Vascular Consti­tution of Parts, that I apprehend not how Nature could otherwise have [Page 97]acted without the consequence of a boundless Accretion, inasmuch as that when any parts of a Fluid become extravasate, they necessarily lose much of their progressive motion, and if of a gross consistence, are either pro­scrib'd by the wider passages, or of a finer, through those more straight and elaborate (viz.) by Transpiration; so that what Particles of Matter so­ever continually arrive, for either the augmentation or reparation of the Parts, must (unless the ruine of the Subject do not first happen, as we see it often does in Diseases proceeding from such Causes) needs (if not confin'd in Vessels) ad­vance into a monstrous preternatu­ral accumulation, as being, by reason of their gross consistence, altogether uncapable of being carried off proportionably to the measure of their aggestion, in the form of subtile Steams or Exhalations.

Besides a rational explication of the natural Functions which this Hypo­thesis furnisheth us with, it also, seems to clear a great many Difficulties which have hitherto puzzel'd the most refined Physiologists relating to [Page 98]the Animal Faculty, such as are Sen­sation and Muscular Motion; of which last here in the next place, the other being reserv'd for the last Chapter, which treats of Sensation and Motion in general.

CHAP. XII. Of Muscular Motion.

TO recite the Opinion of others upon this Subject would be a thing altogether useless here, seeing an Abstract of them is already ex­tant in the Philosophia vetus & nova by Mr. Colbert; and besides, the most correct of them are not only very unprobable, but absolutely re­pugnant to plain Reason and Matter of Fact too; an Instance whereof you may have in Dr. Willis's Tendi­nous Reservatories of Animal Spirits, Willis de Mot. Musc. p. 35. Mayow de mot. musc. p. 73. in Dr. Mayow's Twisting or Fiddle­string Fibres, with whom of late Mr. Regis agrees, by which the Muscle must needs lose a great deal of its thickness, than which nothing is more contrary to Experiment; in Duncan's first and second Element of Des Chartes, Dunc. p. 90 which he makes the Animal Spirits to consist of, contrary even to the very Principles of that great Man's Philosophy, which al­lows [Page 100]no Elasticity to those Bodies themselves, though the Authors of it in all others; likewise in Dr. Croon's making the Blood it self, Croont, p. 23, 24, 25, 33. Philos. c [...]. p. 23. as well as the Animal Spirits, to be mov'd by the power of the Soul to any Muscles; as likewise the extravasa­tion of those two Liquors first into the spaces betwixt the Fibres, and then their introvasation into the Fi­bres themselves again, in order to make inflation, an Error incident to the Immortal Borellus also, Borel. de mot. Ati [...]. p. ult. prep. 23. & [...] ­ribus [...]l [...]s loci [...]. whose ima­ginary Discourse upon this Subject seems of a very different Thread from the rest of his Excellent Works.

If therefore what hath been alrea­dy said about the Structure of Parts be remembred, (viz.) That the Me­dullary Part of the Brain is only a Contexture of Vessels; that its Ner­vous Propagation or Nerve is also a Compages of Vessels, formerly call'd Filaments, much more narrow than those of the Brain it self; and, that these Nerves produce, or at least terminate in the Fibres of all sorts of sensible Parts whatsoever, though of a different texture, as [Page 101]well as those carnous ones of Muscles, which last are tubulous, 'twill not be in the least unreaso­nable to inferr, That these Bo­dies being kept continually turgid with the contained Fluid, are equally capable of transmitting or receiving Impressions of the Object, as if they were stretched longitudinally like a Bow-string from each Extremity, according as Borellus hath obser­ved.

And as to Muscular Motion, allow­ing only what may directly be in­ferred from what hath previously been said, (viz.) That the Nervous and Carnous Fibres are only a con­geries of Fluids contained in certain Vessels communicating with each other, that by reason of a Plenitude in the aforesaid Fibres, the whole Machine is in a constant Equili­brium, it will necessarily follow, upon the common Postulatum, (to which all Mankind must be behold­den upon all such Explications as these to the World's end) viz. that the Sensative or Rational Soul can command the Animal Spirits (which I call only a Nervous Fluid) into a [Page 102] Primus Impetus, or local motion, that a part of that Liquor, when­ever a Muscle contracted is trans­mitted through the Vessels which contain it from the great Reserva­tory thereof, the Brain, to its Car­nous Fibres, into whose Vessels, be­ing so much narrower than those of the Nerves, even by vertue of the same force which moves it from the Brain, that Liquor is driven after a most rapid manner, (which Effect, to any acquainted with the nature of Fluids and mechanical Laws of Mo­tion by Projection, needs not any demonstration) causing the Intume­scence or Inflation of the Muscle, the same Liquor at the same time being driven back again with an equal speed from the Antagonist Muscle into the room of the first, which was transmitted from the Brain to the contracted one, in or­der to maintain the same Plenitude or (which is the same thing in the sence of the old Philosophers) to avoid a Vacuum. And if any object the wideness of the Passage it is to come back by from the reflexed Muscle, as an impediment to an [Page 103]equivalent speed in that Liquors re­trocession, I have to answer, that the Emptiness being made first, is a sufficient recompence for that.

And here I cannot but take no­tice, that all they who contend for Animal Spirits, analogous to those we see produc'd from various Sub­jects by Fire, as the only adequate medium for all sorts of Muscular Motion, have been forced to have recourse either to certain Tracts or Interstices betwixt the Filaments of the Nerves continued from the Brain, or the Original of the Nerves through their whole Productions to the Muscle, of which sort are the Cartesians, or else to a certain Ner­vous Juice, for their place of resi­dence, of which sort are most of the Moderns, and particularly Vieus­senius, by which Passages, or out of which Juice these fine invisible things are either voluntarily, by the com­mand of the Soul, or inadvertently, from several either inward or out­ward impressions, transmitted, in order to produce Motion: which if true, and the only ways of pro­ducing Muscular Motion, I beg leave to ask, how it comes to pass, by [Page 104]either of these ways, that when ano­ther person bends my Arm, and that againfl my Will too, the bending Muscles of the Arm become as tu­mid as when voluntarily or inad­vertently contracted at any other time; which hath been truly observ'd tho' not satisfactorily accounted for, by Dr. Croone, Croone, p. [...] or any other I know of.

But how this or any other sort of contraction of a Muscle happens, does by the other afore-mention'd Hypothesis become explicable, with­out any manner of difficulty at all: For when the Cause of Contraction is from the Command of the Soul, the pressure is first from the Fluid in the Brain, by which all the inter­jacent or continued Fluid slows to­wards the Part to be moved, the same proportion of Fluid being at the same instant transferred into its room from the relaxed Muscle; and when the contraction of the Muscle is from the above-mention'd external force bending the Arm against my will, then the Liquor contained in the relaxed carnous Fibres or Vascula is transmitted through the whole con­tinuity of Fluids, to that which is contracted, and all this without being [Page 105]beholden to the wild Conceits of a dry and moist part of the Nervous Juice, blind Passages, invisible Tu­buli betwixt the Antagonist Muscles or Valves in the Nerves, by a meer Aequilibrium of the Fluids contained in the Vessels the Parts consist of.

At the same time I am not in­sensible of the Solution some have given this Instance of Involuntary Motion upon another Hypothesis, (viz.) by supposing an equality of Tension or Elasticity in all the Muscles of the whole Body; by which means it falls out, that when any new additional force (though never so small) is added to the Fi­bres of any Muscle, as in voluntary motion, or the power of Elasticity in the Antagonist Muscle, overcome by outward force, as in the afore­mention'd Instance of Involuntary Motion, the other Muscle then be­comes contracted.

Now, that this is one concurrent Cause in both sorts of Instances, as being confirm'd by the Experiment of cutting a Muscle through, either towards the Extreams or in the mid­dle, by which the Fibres, by their [Page 106]natural Elasticity, are found to con­tract either to one or the other, or to both Extreams, is allow'd to be true; but to be the only Cause, is altogether as false.

For, in the first place, as to the case of voluntary Contractions, it is allow'd to proceed from a transmissi­on of Spirits from the Brain into the carnous Fibres, (that Hypothesis of Steno to the contrary having been convicted long since by Borellus, in his Book De Motu Animalium) though not without the concurrence or sym­praxis of the natural Elasticity of the Fibres belonging to the Muscle to be contracted.

So likewise, without the trans­mission of Animal Spirits from some force or another, I deny even the pos­sibility of that stiffness or hardness which is easily preserved in all con­tracted Muscles, feeling and seeming as though they were indurated and swelled out, as really they are, whe­ther it be in the case of voluntary or involudtary motion; in confirmation of which, I affirm, that though by the cutting of the carnous Fibres of any Muscle through, which way so­ever [Page 107]it be, the contracted part may, and doubtless does, grow thicker by the shortning of its Fibres, yet by that means only it does not become stiffer and harder, so as we find Muscles do when contracted by any natural Cause, nor is there any ne­cessity it should do so, according to any Rules of Mechanism, seeing the Fibres shortning only by their own elastick force, when they find the circumambient space give way have no necessity of subintration of parts, which is always requisite to procure a stiffness or hardness to a part al­tering its dimensions as Muscles do, from a longer and thinner to a shor­ter and thicker circumference; and upon this it must needs follow, that in a Muscle contracted by involun­tary force (in which Action the Brain is altogether unconcern'd) that stiff­ness or hardness then perceivable in it, must needs be owing to the Fluid or Spirits in the antagonist Muscle, after the manner already explained, transmitted to it.

Now, to define what sort of thing this Animal Fluid (so called) is, I see no occasion to frame any other Idea of it than what we ordinarily have of the purest Liquors, seeing the Nerves are a Substance which (to the Senses of either Smell or Taste dis­covers very little else than what is insipid) are always reckon'd amongst the least hot parts of the Body, and doubtless far less warm in Fishes than us, who yet have as great a stock of Animal Spirits as any other Crea­tures. And this Consideration may be it was that occasion'd an Author to give the Animal Spirits the Epi­thite of Frigidiusculi. Du His. T. l. p. [...]

'Tis plain enough, that the Vessels which contains this Fluid are extream minute, and consequently the Con­tent must needs be of a very fine and depurate consistence, though without much resemblance to either the aforesaid nimble, saline, or sul­phurous Productions of the Fire.

'Tis in a continual, gentle, direct motion, though perhaps contained in curved or reticulated Vessels, from its original source to the ends of the carnous Fibres, from whence [Page 109]it is convey'd into the Membranous or Tendinous Productions, according as the Fibres terminate, and it may be by filtration only; in which, as in other, and particularly in Glandulous Parts not subservient to Muscular Motion, where Nervous Ramificati­ons are very copious, whether it be of any other use than to keep the Parts in their proper tone, in order to their regular discharge of the office of Secretion, must still remain a Con­troversie, notwithstanding all that hath been yet advanced against it, inasmuch as wastings and numbnesses of Parts, the common Symptoms of obstructed or divided Nerves, (which doubtless by their hastening through such Causes to Muscular Parts, gave the first rise to that Conjecture about the Existence and Use of that Juice throughout the whole Body) are equally explicable by the want of Tone, as of that supposed Liquor.

To the proof of all this an Ex­periment frequently made does not a little contribute, and that is the injecting the Arteries of a Dog, or any such Creature, when dead, upon which there immediately hap­pens [Page 110]a contraction of the Muscles, according to the different strength of them, (viz.) of the Extenders in the hinder Legs, and of the Ben­ders in the fore Legs, though the In­jection be only of cold Water, the reason of which effect in particular, if it be remembred what hath been before observed, (viz.) that the Blood-vessels do most certainly enter the composition of the Nerves them­selves, will not only become very easily explicable, but the whole Hy­pothesis at least very highly pro­bable.

If it be said, That this speedy in­stantaneous reflux of the Animal Fluid is opposed by the aforemen­tioned constant direct motion it hath from its Source to the parts to be moved, 'tis easie to reply, That its slow direct motion that way is casily overcome and repel­led by the violent impulse of the forcibly-relaxed Muscle the other way.

If further it be demanded, by what means it so happens that in the Instance before us of an Arm bent by force, that the refluent Ani­mal [Page 111]Fluid is rather towards the Muscle, which by that means then proves contracted, than towards any other whatsoever, to all which it may indifferently have access, I think the Solution seems not difficult, if it be consider'd, that at the same time that the one Muscle is forced from, the other is forced into a contracti­on; from whence it so falls out, that the carnous tubulous Fibres of the last, which by being extended un­der the state of relaxation, did lose their cavity, must needs by their natural elasticity, when freed from the preponderant force of its Anta­gonist, acquire it again, by which means a space being made, the re­pelled Fluid, by the Laws of Libra­tion, (to say nothing of the habitual motion of the Animal Spirits, or Liquor, by most Authors, especially Borellus, urged as a Reason for this effect) must needs be driven thi­ther.

In fine, though I am not averse to think most of the Phoenomena relating to Sensation and Motion may be solved by this Theory, tho' of so small an apparatus, yet I am so [Page 112]far from being fond of it, that I have reserved a far greater share of Friend­ship for any other that may seem but of never so little more a kin to Truth, and submitting all I have said on this Subject to the candid Sentiments of the more judicious Proceedee in de­scribing the other parts of the Brain as they offer themselves in the usual modern way of Dissection.

CHAP. XIII. Of the Brain in particular.

THIS Part being already de­scrib'd and consider'd in ge­neral, as consisting of two different Substances commonly called its Si­milar Parts, and the Source of all Sense and Motion, comes now to be taken notice of in a more particular manner, with respect to its dissimi­lar parts or conformation; and this I think may best be done first accor­ding to its outward, and next to its inward appearance.

Outwardly 'tis convex and corti­cal, exactly divided into two Hemi­spheres by the first Process of the Dura Mater called Falx, from the bony Process called Crista Galli for­wardly to the very hindermost part of the Cranium, where these two Di­visions are stretched over the Cere­bellum, from which part also 'tis per­fectly separated by the second Process of the Dura Mater, to the end it [Page 114]may not cause any prejudicial com­pression upon that part, either by its weight or pulsation.

The foremost Division is made on­ly as deep as the Corpus Callosum, the latter to the very Medulla Oblongata it self.

'Tis further imperfectly divided into four Lobes, two whereof (which being the less) are forwardly, and two (which are much bigger) backwardly.

These Divisions appear best in the inverted or Varolian Dissection, being marked out as it were by four Bran­ches of the Carotid Artery, two be­fore, and one on each side.

These I call Imperfect Divisions of the Brain, because though the Pia Mater runs betwixt them, together with the aforesaid Branches of the great Artery, yet they adhere by several Fibres, both of that Mem­brane and the Blood-vessels them­selves.

'Tis also imperfectly divided thro' all its external cortical part by the Pia Mater, though not so profound­ly, to the end the Blood-vessels may penetrate this part in more sine and reticular Ramifications; and that by [Page 115]the pulsation of the Arteries the in­terjacent cortical Glands, (or rather Vessels) may more freely make their proper Secretions.

Nextly, it may be consider'd in its inward appearance, which is con­cave and medullary, taking its origi­nal from the Extremities or Apices of the Medulla Oblongata, (or rather a little more forwardly from the fore­most part of Vieussenius's oval Center) commonly called Processus Lentifor­mes, or according to Dr. Willis, Corpora Striata.

From hence 'tis presently reflected back on each side in the form of a Vault, very near as far as the Nates and Testes, a little below which on each side 'tis joyn'd with the Crura Medulla Oblongata on their under side, being continuous there to those Parts commonly call'd the Crura For­nicis.

The middle and uppermost part of this Medullary Substance, by the Ancients always called Corpus Callo­sum, is therefore by Vieussenius cal­led Fornix Vera, Vicus. p 61 par. 1. in his Opinion sustaining that Office (though I see not that it does, or for the Reasons [Page 116]before given in the description of the Dura Mater and 'its Processes, needs to do any such thing.)

This is that part which, as was before noted, was thought (but mi­stakenly) by Vesalius and others to escape the covering of the Pia Mater and in it are not visible any bloody Specks, as in most other parts of the Medulla Cerebri.

'Tis the medium uniting the me­dullary part of each Hemisphere or Division of the Brain, famous for the transverse Stria running through it from each side of the aforesaid Hemispheres, the Septum Lucidum only coming between.

In this large or principal Cavity are contained the three Ventricles, the Fornix, the Septum Lucidum, Corpora Striata, Thalami Nervorum Opticorum, the Roots of the Fornix, the Tractus Intermedius of the Corpora Striata, the Tractus Medullaris Tha­lamis Nervorum Opticorum Interjectus, (which last has bin already described) the Vulva, Anus, and Rima or Passage to the Glandula Pituitaria by the In­fundibulum, and Glandula Pinealis, (which also hath already been descri­bed) of all which briefly in their order.

The three Ventricles, FIG 5. AA by cutting asunder the Fornix near to its Roots, and turning it backwards over the Nates, The three Ventricles. Testes, and Glandula Pinealis, appear to be but one, those on each side it being called the Laterales, in which are the Corpora Striata Tha­lami Nervorum Opticorum and Crura Medulla Oblongata, that Rima, so far as 'tis covered with the Fornix and parts the Crura Medulla Oblongata, being the third.

From the extream Limits of these two side Ventricles, Vieuss. T. 10 AA, &c. from before to behind, Centrum Ovale. does arise that medullary space called by Vieussenius, Centrum Ovale, in his Opinion the great Dispensatory of Animal Spirits, the fore part whereof Willis calls Limbus anterior corporis striati. Will. De An. B [...]ut. p 42. T. 8. F.

The Fornix is a medullary part arising from two Roots in the fore­most part of the Basis of the Brain, The Forix. FIG. 5. AA, bb. lying betwixt and upon the upper­most parts of the Thalami Nervo­rum. Opticorum, which Roots come out of the foremost part of the Geminum Centrum semicirculari, so called by Vieussenius, like two large [Page 118]Nerves, and afterwards joyn toge­ther, constituting a broadish medul­lary Body, which after having first projected it self for some space for­wardly betwixt the Corpora Striata, and afterwards run the length of the third Ventricle, growing all the way broader and broader, and towards its edges (by Vieussenius called Fimbrae) thinner; Vi [...]ussu Tab 6. D and being reflected backward towards the hinder part of the lateral Ventricles, like two Arms, commonly called Crura Fornicis, the beginnings whereof on each side are by Auran­tius called Hippocampi and Bombyces, Aura [...]. Anal. O [...]. p. 45. (from whence, I know, he had chiefly observ'd this part in Brutes, in which, by vertue of the hinder part of the Fornix, in that place growing somewhat thicker, and running over the hinder and upper parts of the Th. Nerv. Opticorum, which are more pro­minent in them, as in Sheep, Calves, &c. than in Men) it is made to appear on each side like the bending Crest of the Sea-horse, and is in colour much like the Silk-worm. certain minute Stria's, Malp. de C [...]r [...]b. p. 5. which Malpighius calls Fi­brae, crossing them like Rings ob­liquely, contrary to what the same [Page 119]Author's Account is of them, who says those Fibrae or Striae run upon them otherwise, viz. as they do on the Septum Lucidum ( i. e. longitudi­nally) and embracing the Th. Ner. Opt. on their upper part on both sides, but adhering close to them as one con­tinued Substance on their under part, (in which place they are called, by Vieussenius, Vieus. p 61. Posteriores veri fornicis (viz. Corporis Callosi) Columnae) be­comes there continuous with the hinder part of the Corpus Callosum, where it winds down upon the sides of the Crura Medulla Oblongata, Ibid. and makes up that undermost space or cavity of the two side Ventricles, by the said Aurantius called Ventri­culi Hippocampi or Bombycini, and Vieussenius called the hinder part of the Centrum Ovale, which by that kind of curved passage loses some­thing of its oval figure.

The Sep­tum Luci­dum.The Septum Lucidum some of the Moderns think to arise from the Fornix, thence ascending to the in­ternal Superficies of the Corpus Cal­losum; others from this last descen­ding down to the Fornix, but most [Page 120]likely from this last, where towards its foremost part I have always sound it double, (first taken notice of by Sylvius de le Boe) and as Vieusse­nius truly says, Sylv. dele Boe Disp. Med. p. 19. par. 1. Thes. 13. often with Water in its duplicature.

'Tis a very thin, medullary, transparent Body, intermediate to the Corpus Callosum and subjacent Fornix, by means whereof the two lateral Ventricles are in that place separated one from another.

The Corpora Striata, The Corpo­ra Striata, FIG. 5. I 1, &c. or Processus Lentiformes, are two Prominencies situated something higher than, and in Men a great part of them on each side (though Dr. Willis says, where the Corpora Striata ends the Thalami Nervorum Opticorum begins, which is only so in Brutes) of the Thalami Nervorum Opticorum, or Juga Crurum Medullae Oblongatae, and are so called from the many white Streaks ap­pearing in them, descending oblique­ly to the Medulla Oblongata, with Cineritious Substance coming be­twixt them when they are cut ho­rizontally.

They run down on each side the Thalami Nervorum Opticorum as far as till the Corpus Callosum be­gins to wind back upon the Crura Medulla Oblongata, towards the hin­dermost part thereof.

I have got them delineated here exactly true, (tho' by neglect without the Striae) finding all the Cuts of them in Willis to be from Brutes, except one, which is done very ill, and those in Vieussenius very false, unless in Fi­gure the 8th, which also wants the Striae.

The Thala­mi Nervo­rum Opti­corum.The Thalami Nervorum Opticorum are two prominent Bodies, more purely medullary on their outward Superficies than within, which meet­ing together like the two topmost stroaks of a Y inverted, constitute the uppermost part only of the Crura Me­dulla Oblongata in that form, the other or undermost side being quite of another figure; and seeing they are the immediate continued Pro­ductions of the Medulla Globosa Cere­bri, (which contrary to the old Opi­nion of Praxagoras and Philotimus, asserting the Brain to be only a Ger­mination [Page 122]of the Dorsal Marrow, of late reviv'd by Bartholine, Causab. [...]n Athan. p. 137. (if any prece­dency of Parts as to time may be al­low'd) I look upon to be rather the original than the production of the Medulla Oblongata and Spinalis too) and may more properly be called Capita than Crura of the Medulla Oblongata.

The Tops or Juga do, FIG. 5. cc. as already observed, encline close, yea, joyn together, as Vieussenius hath rightly observed contrary to Willis, (whose Figures of that part are utterly false) unless where the Rima ad In­fundibulum parts them, leaving like the Corpora Striata an obtuse angle between them.

Betwixt these two last mention'd Bodies there is a medullary space on each side, which in a bending man­ner encompasses the Thalami them­selves, and receive the Extremities of the Striae in the Corpora Striata, as they descend from the afore­mention'd Centrum Ovale, and is therefore by Vieussenius called Gemi­num Centrum Semicirculare, Vieus. p. 67. par 2. Willis de An. Brut. p. 42. T. 8. [...]. by Willis Limbi Posteriores Corporum Stria­torum

The reason why they are called Thalami Nervorum Opticorum, is from certain Fibres supposed to be in them, arising both from their true medullary Superficies (by Vieussenius call'd a Medullary Membrane) and some from within their own Sub­stance, which at last, towards their foremost part meeting together, make up the Bodies of the Optick Nerves.

Willis says nothing of these Fibres, though in his Opinion Galen did not improperly give them that name. Vieussenius paints them very strong.

As for my part, I never could find any Fibres at all appearing in their external medullary part, those within are very small at best, and scarce discernable.

On the outside of these I have al­ways found and often showed a very fair medullary Tract, A Medul­la [...]y Tract. Tab. 5. mm here descri­bed, running all-along betwixt the Corpora Striata, &c from the very hin­dermost extent of the Corpora Stria­ta forwardly, down to the very Roots of the Fornix, to which they seem to be continuous.

The Passage into the In­fundibulumWithin this Cavity of the Brain are likewise two passages into the Infundibulum, and so on to the Glan­dula Pituitaria, the foremost of which is called by the odd Name of Vulva, The Vulva. and the hindermost of Anus, The Anus. from their situation, which with the Rima betwixt them, is cal­led, as was before noted, the third Ventricle.

The places whence all this Water issues are commonly by the latter Anatomists described under the name of Tria Foramina, Tria Fo­ramina. situated so as to give passage from all the eminent Regions of the Brain, from whence there can be access had to them for the Water (or rather the Lympha, properly so called) to fall into the aforesaid Infundibulum, the first where­of is behind the Testes, under the Val­vula major, (hereafter to be descri­bed) the other just under the Pineal Gland, or the beginning of the Rima, which two meet in an Aperture, under the Nates and Testes, Vieus. p. 73. par. 3. by Vieus­senius call'd Aquae Emissarium, having a steep descent into the Infundibu­lum; and the last at the end of the [Page 125] Rima, or just under the Roots of the Fornix, and all ending at length (tho' by two different passages) in the In­fundibulum.

It may not be unseasonable in the next place to take notice of two remarkable very fair Processes, The Nates and Testes Tab. 7. CC called Nates and Testes, by former Anatomists so named from the re­semblance they had to those parts; but it is plain from thence they were only used to dissect Brutes, in which they have such a proportion as is betwixt them; whereas in Men 'tis plain they are very near of the same size, and not very different in form, being oblong and accumi­nated towards their Extremities; but in Sheep, Calves, and most other Creatures the Nates are round and large, and the Testes oblong, somewhat accuminated, and very small.

Before these Natiform Proces­ses, under the Glandula Pinealis, runs a transverse Process before taken no­tice of Pag. 84, Vieussen. Tab. 8. f by Vieussenius called Processus Natibus Antepositus, and Nervuli Aemulus, which upon fur­ther enquiry, by drawing the Thala­mi [Page 126]Nervorum Opticorum still wider, appears to be rather Nervi than Ner­vuli Aemulus, being as thick as that behind the Roots of the Fornix, to which in situation 'tis just opposite, and seems to joyn the Thalami Ner­vorum Opticorum together, as that does the Corpora Striata.

In what rank to place them 'tis hard to say, as being neither proper Appendices to either the Brain or Ce­rebellum, properly so called, and being divided from the Medulla Oblongata in some measure by an In­terstice commonly called Ductus ad Infundibulum by the Moderns, but by the Ancients a Passage for the Animal Spirits to the fourth or noble Ven­tricle.

They are situated upon that part of the Medulla Oblongata which is be­tween the Cerebrum and Cerebellum, The Is­thmus. which space was before called Isthmus, opposite to that part called from its Author Pons Varolii, and by many Authors, as Bartholine, Spigelius, Highmore, &c. thought to be the two hindermost Roots of the Spina­lis Medulla, which much more likely Riolanus makes the Processes of the [Page 127] Cerebellum to be, Visalius p. 766, 767. fig. 10. AA, I, K. & fig. 11. GG. and with him the great Vesalius, who paints them so.

From this intermediate situation Dr. Willis thought sit to make them as it were an Intelligence Office be­twixt the Cerebrum and Cerebellum, how rightly, I refer to the Judgment of others.

'Tis certain they are medullary Bodies, and contribute to the ma­king the Animal Fluid or Spirits so called after the same manner as the rest of the Brain does; for in cutting them through, (after having taken the reticular expansion of Blood­vessels off from them, which is very large here, and eminently conspicu­ous in injected Brains) I find them of the very same substance with the Processus Annularis and the Thalami Nervorum optici, partly cineritious, and partly medullary, and in fresh Brains somewhat, but very faintly, striated.

I know not of any part within the Brain, properly so called, that is not already described, except a certain Medullary Chord at the end of the third Ventricle, and the Valvula [...]ajor.

Commis­lura Cras­sioris Ner­vi Ae nula of Vieusse­nius. The first of these is a Medullary Process, Willis p. 43 col. 2. Vituss. p. 83. which joyns the Corpora Striata together, according to Dr. Willis, by Vieussenius called Comissu­ra Crassioris Nervi aemula; and ac­cording to him is the Medium or Commissura by which his Geminum centrum semicirculare intervening be­tween the two Corpora striata, supe­riora anteriora & posteriora, and his Tractus medullaris transversus & ob­liquus intervening between his two Corpora striata inferiora anteriora and posteriora, have a communication with each other.

Dr. Willis places this Chord or Commissure under the Roots of the Fornix, but it is always behind it, Willis, p. 6. col. 1. tho' contiguous to it.

The second is the Valvula ma­jor, The Val [...] ­la major. so called by Vieussenius, Vieus. p. 76. Willis, p. 49 col. 2. pat. 2 but plainly enough discovered by Dr. Wil­lis long before, and its proper use described.

It is a thick (especially in Men) medullary Membrane, adhering for­wardly to the inferiour part of the Testiforme Process a little be­hind that transverse medullary Process from whence the pathe­tick [Page 129]or fourth Pair of Nerves arise, laterally to the Process ascending from the Nates to the Cerebellum, on its hindermost Expansion, to the foremost Vermicular Process of the Cerebellum, and no where that I know of to any part of the Pous Varolii, as Vieussenius will have it, Vieussen. p. 76. Id. p. 73. par. 3. (who seems to have mistaken another part for that Process) unless just where the second Process of the Cerebellum comes out from thence, which jointly with its fellow Process on the other side, when they meet together, after their transverse descent on the back­part of the Medulla oblongata, do really make up that part which by Willis is call'd (and that no doubt from Varolius) Protuberantia Annu­laris, and by others, from its true Author, Pons Varolii.

By raising up the foremost above-mention'd Vermicular Process of the Cerebellum with the Finger, it rarely fails to come in sight; but if not so, 'tis easily shown, by blowing into the Foramen situated under the Pineal Gland.

Its use, according to Vieussenius, Vieus. p. 110. par. 2. is to hinder any part of that Water which falls into the hindermost Fo­ramen [Page 130]behind the Testes, from run­ning into the fourth Ventricle, or Vice versa from the fourth Ventricle into it, or from getting out on each side of the Medulla oblongata, over the afore-mention'd Processes, so as to fall down upon the Nerves arising thereabouts below from the Medulla oblongata: Which last use is evidently most true, (whether it be understood of Water preternatu­rally or accidentally collected there, for I must needs confess I could never find any there, any more than I could in the third Ventricle in Subjects free from those Diseases incident to that part, as hath before already been re­marked p. 82) but as to that relating to the passage from the Cerebellum to the last or third Foramen, I much doubt the Truth of it, for many Rea­sons, of which this is one, viz.

That the Plexus Choroeides in the fourth Ventricle, together with the adjacent Parts, being of the same Texture as the other are in and about the two lateral ones of the Brain, renders it as reasonable to suppose that Water may be collected there as in other parts of the Brain, (nay, that it is so, he himself also allows as Mat­ter of Fact) and consequently as ne­cessary [Page 131]to have a place of vent for the Water whenever it happens to gather there, as it was for that which was at any time got into the other Ventricles. And consequently,

In the next place, I do not see how this tender Film can be able to intercept a passage of so search­ing a body as Water at any time forced against it (notwithstanding the supposed declivity of this Part, which in Man, by reason of the largeness of the subjacent prominent annular Pro­cess, is very inconsiderable) which by Pulsation must needs happen whenever we suppose that Cavity filled with it.

And, in the last place, notwithstan­ding all the Contrivance the afore­said Author hath shewn in conveying the gross part of the Water (which, as was before noted, he grants may be, nay, constantly is deposed there from the Glands of the Plexus Choroeides here situate) by the Extremities of Veins, out of this Ventricle, Vieus. p. 111 I am suspi­cious, if there was no spedier reductory passage found out, there would fre­quently happen very great Mischiefs to the Medulla Spinalis it self, and the Nerves springing from it, seeing the Extremity of that Ventricle cal­led the Calamus Scriptorius is there [Page 132]parted from the Spinal Marrow be­hind it, but only by the Pia Mater, which notwithstanding it is there dou­ble, as it is also quite down the whole Spine, lest perhaps the Water should fall down upon the Nerves which arise from it too readily, yet upon such an occasion may be easily suppos'd subject to violation. Not to say any thing of the high improbability of any such Conveyance at all by the Veins, seeing that in a natural state they are always, as hath been already observ'd, conti­nuations only of Arteries.

'Tis true, this may binder the fall of Water into the fourth Ventricle, by reason of a Passage under the Nates before mention'd, by Vienssenius call'd Aquae Emissarium, so near at hand to receive it when it finds its further pas­sage that way obstructed by the in­terposition and resistance of this Valve. And for the same reason doubtless it was, that in Vieussenius's Experiment which he brings for a Proof of his Opinion, no Water was found in the sourth Ventricle, Vieus. p 110 par. 2. it ha­ving got a passage immediately, upon its non-admittance by that Valve, to convey it another way, which by rea­son of the steepness thereof, is done much more read [...]ly.

CHAP. XIV. Of the Cerebellum.

THE Cerebellum falls next in order to our consideration, in describing of which I hope a great deal of pains may reasonably be spa­red, seeing all that hath been alrea­dy spoken of the cortical or cineri­tious part of the Brain, as also of its medullary part, is equally applicable to the Cerebellum. Nor is what hath been said already of the Plexus Cho­roeides in the Ventricles of the one part less applicable to that Plexus in this.

The Plexus Choroeides of the Cerebellum.This Plexus Choroeides in the fourth Ventricle begins to be glan­dulous just under the Eighth Pair of Nerves, from whence it runs up on the side of the Caudex Medullaris to the chordal or third Process of the Cerebellum, and from it enters the fourth Ventricle, Aurant. Anatom. Obs. p. 48. by Aurantius called [Page 134] Cisterna Spirituum, (which Ventri­cle, conformably to what that Au­thor hath in the aforesaid place ob­served, I always find broader than long, and double, though not divi­ded by any intervening Body, as the two lateral ones of the Brain are;) not lying loose therein, nor at the bottonn of it, as the Plexus does in the Ventricles of the Brain, but quite contrariwise, (and which hath not heretofore, as I know of, been taken notice of) adhering close to the top of this Ventricle, or the bottom of the superincumbent Cerebellum, then running transverse just at the end of the Calamus Scriptorius, there be­comes continuous to the Plexus of the other side; as hath been observ'd of the Plexus in the lateral Ventricles of the Brain.

This Plexus arises from a ramifi­cation of the second or backwardest Branch of the Cervical Artery, as one part of the other Plexus of the Brain mention'd in that Chapter where the said Plexus is treated of, doth) and another smaller Branch of the said Artery about the place where it ascends from the Verte­brals, [Page 135]which last Branch turns in­to a reticular Expansion first, FIG. 1. q and then a little space further meeting with the other, constitutes this Plexus.

This part differs from the Brain in its cortical structure, inasmuch as its Interstices are here eliptical or pieces of imperfect Circles, growing shor­ter towards those two Productions of the Cerebellum, before and behind, (which by reason of certain annular depressions occasion'd by Bloodvessels there embracing them, seem as tho' they were wrinkled like Worms, and therefore called Processus Vermicula­res) as Parallels upon the Globe do towards each Pole.

The three Processe of the Cere­bellum.It hath three Processes, which joyned together on each side, make up as it were two fair Roots, accor­ding to the Ancients called the hin­der Roots of the Oblongata Medulla, by the Moderns Peduncles or Stalks, by which this part grows to the Me­dulla Oblongata.

The first of these ascend from the Cerebellum to the Nates, FIG. 7. gg the se­cond from the Cerebellum to the Medulla Oblongata, FIG 6. BB. which meeting together on the under side thereof, [Page 136]as was before noted, make up that large Protuberance by Willis called Processus Annularis, Var. Anat. p. 26. by others from the first Author Pons Varolii.

This I sind full of Stria's or me­dullary Tracts, F 10.6. cc much stronger and larger than those of the Corpora Striata, running transverse on each side the length of the whole Pro­cess, and terminating in a medul­lary long Tract, dividing that Pro­cess into two equal parts, as you see in the Figure, Ib. cc the use whereof, as having never been before obser­ved will be hereafter taken notice of.

The third descends from this part backwards, Ib. ss FIG. 7. hh upon the upper side of the Medulla Oblongata, like two lon­gish thick Chords on each side, ma­king the Medulla look somewhat thicker and broader in that place, and not unfitly stiled the Chordal Process.

These Stalks, when they joyn together at the other end, make up the Meditallitum or Corpus Callosuas of the Cerebellum.

The trans­verse Pro­cess of the fourth Ven­tricle.There are two or three fair medul­lary Processes close to, and sometimes [Page 137]riding one over another, a little on this side the fourth Ventricle, or about the beginning of the Calamus Scriptorius, which joyn the two cesses together that descend from the Cerebellum to the Medulla Oblon­gata; and there are two more de­seending length-way from that other transverse Process behind the Testes, down to these.

[...]w Pro­cesses on the inside of the [...]edulla O [...]ongata.These long medullary Processes I never find wanting, though in diffe­rent numbers, sometimes having seen three, sometimes two, and once I oould find but one, (though larger than ordinary) and constantly, in what number soever, ending in the transverse Processes at the afore-men­tion'd beginning of the fourth Ven­tricle.

These long descending Processes are just over-against the Corpora Pyra­midalia, on the other or under side of the Medulla Oblongata, and the transverse Processes at the beginning of the fourth Ventricle last mentio­ned, are a little above the original of the Eighth Pair of Nerves, insomuch that without being very circumspect one [Page 138]may mistake them for the original of that Nerve, whereas in reality I find them to be the original of the soft or hinder most Branch of the Seventh, as will be more particularly taken notice of hereafter, in the description of those Nerves; and therefore can­not but wonder how Dr. Willis (who speaks in one place as though he had seen them) came to assign them for the Root of the ninth Pair, Willls Ci­rib. Anat. p. 12. col. 2. per. 3. beneath which and this Process I have always observed the space of half an inch.

CHAP. XV. Of the Medulla Oblongata.

THE third part of the Brain, in its general acceptation, according to the foregoing method, is called the Medulla Oblongata, all whose parts on its foreside having already been spoken of, it remains in the next place that we take no­tice of it on its other side, where are most considerable its Crura, Crura Me­dulla Ob­longata. so cal­led, which Crura are only the un­der part of the Thalami Nervorum Opticorum before described, which in their Extremities becoming continu­ous to the under side of the medul­lary hinder part of the Brain, occasion'd the Ancients to think the Medulla Oblongata had its foremost Roots immediately from the Brain there, as it had its hin­dermost from the Processes of the Cerebellum; but upon a more dili­gent enquiry it appears, that these [Page 140] Crura are more deeply immerged in and knit to the Medulla Globosa of the Brain forwardly, by vertue of the Corpora Striata, as also by the very medullary part of the Brain it self, which there, from the back or undermost winding part of the Cor­pus Callosum is perfectly mingled with it.

Where these two Crura begin to come close together, the Protuberan­tia Annularis, FIG 6. BB or Pons Varolii, made up of the second Process of the Cere­bellum aforemention'd, begins to cover the Medulla Oblongata for about the space of an inch and an half, after which this Medulla Ob­longata in one large Trunk is conti­nued to the first Vertebra of the Spine, and so quite down to the end thereof.

Whilst the Brain is in this position it may not be unseasonable to take notice of two fair white Bodies on this side of the Infundibulum, The two white Bo­dies behind the Insun­dibulum. FIG. 1. bb in that depressed part of the Brain, where the Pia Mater (as hath before been taken notice of) is so remarkably double.

There are also two white long medullary Processes called Corpora Pyramidalia both by Willis and Vieussenius, The Cor­pora Pyra­midalia. FIG. 1. n. which arise just at the ending of the Annular Process run­ning down upon the Med. Oblongata the space of an inch, ending a good space below the place where the Eighth Pair of Nerves begin, which have their original between the Corpo­ra Olivaria and the Chordal Processes partly on the other side thereof, con­trary to the account we have of them by Dr. Willis, Willis, p. 13. col. 1. par. 1 p. 61. col. 2. par. 3. who describes them as ending in pointed Extremities, just where those Nerves have their original.

On each side of these appear plainly the Corpora Olivaria, The Cor­para Oli­varia. I [...]d. o. so cal­led from their Figure, as the for­mer were by Vieussenius, which with the Corpora Pyramidalia and two white Bodies behind the Infun­dibulum, he calls Conceptacula Spiri­tuum Animalium, or places contain­ing Animal Spirits upon several occasions of use to the Brain, both in its natural and intellectual Fa­culties.

CHAP. XVI. Of the Nerves.

IN the same position of the Brain we also have a sit time of ta­king a view of the Nerves, which are still medullary Productions of the Brain dispersed to all the parts of the Body, which have need of either Sense or Motion, and these are in number ten Pairs or Conjugati­ons, having their Names and Origi­nals as follows.

The first is the Olfactory Pair, which after they leave the former Lobes of the Brain, and begin to run to the Bone called Ethmoides, take the name of Processus Mam­millares; but this is chiefly in Brutes, where through their largeness they have that appearance, and are manifestly hollow.

By the utmost Scrutiny I have been able to make, they have but one Original, and that is from the undermost and foremost part of the [Page 143] Crura Medulla Oblongata, where they advance on each side into the Globous medullary part of the Brain, from whence running concealed betwixt its foremost and hinder Lobes ob­liquely, for a good space, at last they come in sight, as you see them in the Figure: And by what means Vieusse­nius comes to find such diffused Ori­ginals for them as he speaks of, I know not.

Their Use is known to most, and a particular account thereof, as of the rest, together with the man­ner of Sensation, with relation to the external Organs of Sense, is much more fit for a Physio­logical Tract than one of this kind.

I shall therefore only at this time give a general description of the Nerves belonging to the Brain, how and where they arise, the difference or variety whereof serve very well to inform us, according to several late Theories, concerning the diffe­rent Reservatories of the Animal Fluid or Spirits, and the different dispensation of the same to several parts of the Body.

The second Pair are called the Optick or Seeing Nerves, The Second Pair. Ibid. 2 2. of which I sind no more Originals than of the former, and that is from those me­dullary parts called Thalami Nervo­rum Opticorum, tho' Vieussenius says they are from several parts; and Wil­lis in general terms from the afore­said Thalami Nervorum Opticorum, be­hind the Corpora Striata: which description is more exact in Quadru­peds, where the Thalami Nervorum Opticorum are altogether in situation behind the Corpora Striata, than in Men, where a great part of the Cor­pora Striata are situated on the out­sides of the Thalami Nervorum Opti­corum, and only their Heads or Ex­tremities before them.

The Blood vessels mention'd both by Willis and Vieussenius belonging to these Nerves, I have seen to run not only upon or with them, but also in injected Bodies exactly quite thro' the medullary substance of them, into the reticular Coat of the Eye, wherein they end in an infinite number of the most capillary Ramifications, which by an injection of that Artery [Page 145]made with Mercury, become very delightfully conspicuous to the Eye.

The Nervous Fibres also, from the fifth and third Pair of Nerves, do twine about the Bodies of these Nerves, as the two above-mention'd Authors do truly affirm, but how rightly they both assign to them the office of dilating and contracting them subserviently to the visory fa­culty, and preternaturally in Con­vulsions of the Eye, as though these Fibres were truly Muscles, or of the carnous kind, I refer to the Judgment of others.

These go out of the Skull at its first Foramen.

The third Pair arise out of the forward and upper part of the Annu­lar Process, where 'tis contiguous to, and covered with the under part of the Thalami Nervorum Opticorum, coming out into sight from between them, just where that Process termi­nates forwardly, which is where the Crura Medulla Oblongata come toge­ther into one body, constituting the Caudex Medulloe Oblongatoe.

These running through a duplica­ture of the Dura Mater, on the out­side of the Circular Sinus, go out of the second hole of the Skull to the Eyes, and are therefore called Par Oculorum Motorium, to the voluntary motion of which only they are gran­ted to be subservient, which, seeing they have their original from the Ce­rebellum, afford us no weak Argu­ment against the Hypothesis of Dr. Willis, who hath reserv'd that part in Nerves subservient to in­voluntary motions only.

The fourth Pair is very small, The Fourth Pair. Ibid 4 4. coming from the transverse Process on the foreside of the Medulla Oblon­gata behind the Testes, first coming in sight between the undermost part of the hinder Lobe of the Brain and the Cerebellum laterally, crossing that part where the Annular Process ends towards the Crura Medulla Oblongata, from whence they pass into a dupli­cature of the Dura Mater, and after­wards, a little more outwardly than the former, goes through the same second hole to the Trochlear Muscle of the Eye, and are called from their [Page 147]moving of that according to the pas­sions of the Mind; the Pathetick Pair.

The fifth Pair is broad and large, The Fifth Pair. [...]ld. 5 5. made up of many thick Fibres conti­nuous to each other, some softer than others, arising from the uppermost part of the Processus Annularis, which is backward laterally, where 'tis broadest, by reason of the second Process of the Cerebellum there en­tering it.

This Nerve, The several [...]ches of the fifth Pair. after having first climb'd over the inner Process of the Os Petrosum into a kind of a Cavity made of a duplicature of the Dura Mater in that place, immediately swells into a kind of a thickness, cal­led a Ganglion, Pro. 3. B from whence several Branches are propagated, lying be­twixt the Dura Mater and the Cra­nium, on each side the Sella Turcica, without any Fovea or Cavity at all, going out of the Skull at three several place, Pro. 3. C, D, E its superiour small Branch at the second hole with the third and fourth Pair of Nerves, its inferiour smaller Branch at the third hole, and its posteriour or largest Branch at the fifth.

From the inside of the foremost Branch two little ones turn back, FIG. 2. y. and meeting with another small Branch a little lower turned back also from the sixth Pair, where that Nerve is fasten'd to the outmost or borrowed Coat of the Carotid Artery, make up a small Trunk of a reddish or fleshy colour, like to that which 'tis of when passed out of the Cranium, (as Veslin­gius hath truly observed, The Inter­co [...]tal Pair. X. Z Z. who calls it The Internal Branch of the Sixth pair) which descending obliquely, and cree­ping under that Artery, betwixt its external, proper, and borrowed Coat, goes out with the Carotid Artery at the fourth hole of the Skull, which is in a manner double between the Os Petrosum and Cuneiforme, and from its passage through the Thorax, near the Roots of the Ribs, (all-along which, it receives a Branch from the Intercost [...]l Nerves) is call'd, The Intercostal Pair.

The sixth are about the bigness of the third, The sixth Pair. FIG. 1st. 6 6. arising from the hinder part of the Annular Frocess over-against, and not far off from the beginning or head of the Corpora [Page 149]Pyramidalia. It sends out sometimes one (in this Subject very short) sometimes two slips, as was afore said, for the making up the Trunk of the Intercostal Nerve, and after that (with the foremost Branch of the fifth Pair, in one and the same duplicature of the Dura Mater, together with the preceding third and fourth Pair of Nerves) goes out at the second hole of the Skull, and terminates in the abductory Muscles of the Eye.

The seventh Pair, The seventh Pair. Pro. 1st, 7 7. or Hearing Nerve is large, and comes out al­most just over-against the original of the fifth Pair, on the lower or un­der side of the second Process of the Cerebellum, where it first appears coming out from the Cerebellum to make the aforesaid Protuberantia An­nularis between the Corpus Olivare and that Protuberance, as though it crept out betwixt them, and had (as it really hath) a move remote extra­ction.

It consists of two distinct Proces­ses, the first of which is more round, hard, and less than the second, that being for Motion, [Page 150]this for Sense, but tho' they seem as though they had the same origi­nal, being seemingly continuous at their rise from the Brain, Willis, p. 12 col. 2. part 3 & p. 56. col. 1. par. [...]. (which Dr. Willis affirms they have, tho' sometimes he makes it in one place, and sometimes in another) yet upon a further enquiry it does appear other­wise, the first or hardest having its original from the Caudex Medullaris, not far from the place where it comes first in view; the second very remote from the transverse Process or Proces­ses in the passage to the fourth Ven­tricle before described, FIG. 7. ii (which in another place the same Author seems plainly to have observ'd, Willis, p. 78. col. 1. par. 2 taking it for the Original of the other Pro­cess of this Nerve;) from whence it ascends all-along on the sides of the Medulla Oblongata till it arrives at the afore-mention'd place, where it first, together with the other Branch, leaves the Medulla, to pass out of it at the seventh hole in the Bone called Pe­trosum.

The eighth, The eighth Pair. FIG. 1st 8 8 or Par Vagum, arises a very little beneath the seventh, but yet not from any part of the [Page 151]Annular Protuberance, but exactly in that somewhat hollow place be­twixt the Corpus Olivare and third or Chordal Process, having nume­rous (I have counted ten or twelve) Fibres, but all continuous at their first rise, for its original.

This in a multitude of Ramifica­tions is spent upon the Bowels, and goes out at the eighth hole with the Spinal Accessory Nerve, where the great lateral and the inferiour little Sinus's in the Basis of the Skull go out into the Internal Jugu­lar.

To this eighth Pair about half an inch from its first rise, whilst it climbs upon or sticks to the Pia Mater upon the Basis of the Cere­bellum, ascends a Nerve called Spi­nalis Accessorius by Willis, I [...]id * * but long before him taken notice of, nay, painted and described, by Vidus Vi­dius, Vidus Vi­dius, p. 93. T. 18. Fig. 2. * the original whereof I find to be as far as the seventh Vertebral Pair, from the foremost and hinder­most beginnings of that Nerve, not­withstanding Vieussenius confines its [Page 152]original to the fourth Pair of that part only.

This Nerve runs under the Verte­bral Artery near half an inch on the side of the Medulla Oblongata, at length, about half an inch from the beginning of the eighth Pair, leaves the aforesaid Medulla Oblongata, run­ning obliquely upon the Pia Mater of the Cerebellum, to joyn with the aforesaid Pair, which it really does in that very place, though it part with it afterwards again.

The ninth hath several (in one Body I counted seven or eight) pretty large Fibres for its original, The ninth Pair. Ibid. 9 9. very distant one from another, the first of them coming higher, from the very top of the Corp. Olivare; the next, and several others, are much less, a quarter of an inch lower; and the last much lower yet, about the end­ing of the Corpus Olivare, or begin­ning of the tenth Pair, with seve­ral others between the Pia Mater and subjacent Medulla Oblongata; but af­ter all, its Trunk is very little, about the bigness of the Accessory Pair.

Thro' the Fibres of this Nerve there runs commonly a small but very visible Branch of the Vertebral Artery, at its original; as you see in the Figure expressed by the Letter k on the right side, P [...]o. 1. k. going out at the ninth hole, together with this Nerve and the Vertebral Vein, Vieus. p. 163 which Vein Vieussenius mistakenly makes to go out at a tenth hole, forasmuch as that is never found in Nature, neither need be, seeing the tenth Pair goes out at the last or great Foramen, by which the Medulla Oblongata passes into the Spine.

The tenth Pair, The tenth Pair. I [...]id. 10 10 (which had it a double Original from each side of the Spinal Marrow, (as all the rest of the Spinal Nerves have) might much more properly be called the first Vertebral, inasmuch as that both a great part of its rise and egress is quite out of the bounds of the Cranium) serving chiefly the Muscles of the Neck, it begins with three, and sometimes more, small Fibres lower a great deal, out of the Medulla Oblongata, almost an inch below the Trunk of the ninth Pair, and is about the size thereof.

It goes out of the Cranium be­twixt the first and second Vertebra of the Neck, making its passage through the Dura Mater from the Medulla Oblongata, about half an inch below the place where the said Arte­ry comes in.

The Structure of these Nerves is consistent of many Fibrilla's or Stria's, a certain number whereof being first enclosed in a production of that delicate inward Lamina of the Pia Mater afore described and spoken of, makes up a Fasciculus or Bundle, and many of these colletive­ly the Body of a Nerve.

In these Fibrilla's or Stria's (be­tubulous and always turgid, as in so many Rivulets springing from the main Fountain the Brain, and from thence distributed to every respe­ctive part of the Body) is contain'd the Animal Fluid, by means where­of there is maintain'd a constant intercourse betwixt it and the Soul, and reciprocal acts of Friendship be­twixt one part and another.

This Animal Fluid I look upon only as a Body consisting of very minute and flexile Particles, con­tain'd [Page 155]in such a space as allows them a capacity of being agitated on all sides by vertue of the subtile matter, or Aethereal Globuli they swim in, by which means they are render'd capable of pervading the narrowest Channels of the whole Machine, provided its Orifice or Pore be adapt thereto, in contradi­stinction to those other sort of gros­ser Particles of Matter, which by reason of the narrowness and figure of the space they are to enter, do approximate so close, as to become contiguous in all their Superficies, whereby they become deprived of their former expansive agitation, which is always necessary to make a Body fluid, and like so many small Filaments orderly disposed, do con­stitute the Inclosures or Coats of those Vessels the Fluids are contai­ned in.

This Animal Fluid I conceive to be in a continual state of Transpi­ration, proportionable to the mea­sure of its leisurely production, see­ing no more necessity of ascribing any further Uses to it, besides those afore-mention'd, than I do to [Page 156]the watery Humour of the Eye, besides its service to Vision, which is always in a state of fresh produ­ction, as by the Excellent Nuck's Experiment is plainly manifest; Nuck de Saliv. & Duc. Aqu. Oculor. p. 109. and yet, by vertue of Transpiration, some way or other, though to us not visible, without any incon­veniency to that noble Organ.

CHAP. XVII. Of Sensation and Motion in general.

THE Nerves thus constituted, become accommodated for Use in relation to their several and distinct Functions, in some consisting of Sence only, such as are those appertaining to the particular Senso­ries, (viz.) the Smelling and Seeing Nerves, as also the soft Process of the Hearing Nerve, some Branches of the fifth, and it may be of the ninth Pair, for Tasting; in short, all the Nerves belonging to those external Sensories, by way of emi­nency, and in a less eminent or general way all the Nerves of the whole Body, which are distributed to such Parts as by reason of their structure are capable of Sensation on­ly, any of which, as furnish'd with the Nervous Fibrils, but more eminent­ly the Cuticula, my properly be call'd [Page 158]an Organ or Sensory of Feeling; in others of Motion chiefly, such as are all the whole System of Nerves, (ex­cepting them only afore-mention'd) ses, which though in a less eminent manner, are nevertheless sensitive Nerves also: In others of both, in all respects (viz.) either in a more eminent or less eminent Sensation, and Motion too, with relation to the different Fibres they consist of in their Originals, as the fifth and ninth Pairs.

These two different Functions of Sensation and Motion are executed after two as different manners.

The first of which, being occa­sion'd from external Objects, is dis­charged by a pressure thereof made on the Instrument of Sense, so that the Motion is backward irom one Extream of the Organ to the other, where it terminates in the Commune Sensorium, commonly so called, and is therefore stiled Perception, Passion, or Affection.

The other is discharged by some manner of impulse upon the Organ from within outwardly, with a ten­dency either to acquire some Good, [Page 159]or avoid some Evil; by which Im­pulse, when carried on so far, either in a natural or moral sence, as to ter­minate in, or to be executed upon its proper Object; the Object then may be said to suffer as before in the other case it might be said to act, and the perceptive Faculty now to act as before it might be said to suf­fer, and this Action is commonly called Local Motion.

For whose sake, seeing 'tis of diffe­rent kinds, learned Men have thought sit to organize or divide the Brain into two distinct Provinces invested with several Rights and Jurisdictions abating the Power of the Sensitive Soul, which before was looked upon universal over the whole Brain, al­lowing it only a principal, but no absolute Empire there: And this they have done upon no weak or unrea­sonable grounds, seeing that Local Motion is not only in many respects performed without its assistance, but even against its power of resistance; as in the Pulsation of the Heart, ver­micular Motion of the Bowels, and in a great measure the Act of Respi­ration.

Now, that which hath been taken from the Brain hath been conferr'd on the Cerebellum, to which, though some Power in this Affair may just­ly be allowed, as was before obser­ved, yet possibly not altogether so much as there hath been.

Dr. Willis, who is Chief in this Cause, having distinguish'd Motion into voluntary and involuntary on­ly, hath made the Cerebrum accoun­table for the one, and the Cerebel­lum chiefly for the other; and to that end hath furnish'd it with the like number of Nerves, as in his own words is expressed, Willis c. 1 [...]. Ʋt divisum cum ipso (i. e.) Cerebro, imperium Cerebellum habeat; nay, considering the Intercostal Pair, derived from the fifth and sixth Pair, which belong to the Cerebellum, he hath made it ex­ceed.

I am apt to think that Learned Person too soon fell in love with his first Thoughts, the ordinary reason of either ones seeing false, or not far enough.

Nothing being more apparent, than that most of those Actions of Animal Motions he calls Involunta­ry, and of which he gives so many Instances, are equally found in Brutes and rational Creatures too, whilst in the state of Infancy, as well as when grown up with this only difference, that all of them in the last are under the con­trouling power of the Soul, and consequently may be suspended up­on a reflex'd Act of the Understan­ding; whereas in Brutes and Infants they are necessary, and do as natu­rally ensue upon the impulse of the Object, as Water, when unconfin'd, runs towards a Plain.

Now, if all these were supposed to be under the power of the Cere­bellum only in Brutes and Infants, the Brain it self must necessarily be thought altogether useless in them.

It will be necessary therefore to take notice, that there are two sorts of Animal Motion in Brutes, as in Rational Creatures, the one purely natural, such as is Pulsation of the Heart, and various contraction of the Viscera, proceeding from a certain por­tion [Page 162]of the Animal Fluid continual­ly dispensed to the Nerves in an equal proportion, and so may be said to have their cause origi­nally co-existent with the Creature, and always present: And this kind we find by a most convincing Ex­periment hereafter to be mentioned, to be from the Cerebellum, and ab­solutely free from the dominion of the Brain, in its ordinary way of act­ing or influx.

The other is that of Instinct, relating to the Sensative Soul, or an aptitude of the Nervous Structure, to act according to the Impressions made upon the Nerves, either from within, or from without, and so may be said to depend on the presence of such Causes as are supervenient and extraneous to Nature, suitable to the impressions whereof the Ani­mal either pursues or avoids the Object, obeys, or resists the Im­pulse.

Now, I take it for granted, that no body will deny but that the Nerves (by vertue whereof these last actions of Instinct are performed) whether th [...]y [...]r [...]se from the Cerebrum of Cere­bellum, [Page 163]are equally under the com­mand of the Soul; or else, as I said before, the Brain in those Creatures is to no purpose.

And of this sort I reckon all those actions in rational creatures of Instinct before they have attain'd to the use of their Ʋnderstanding, from any sort of Impressions, or inadvertent and in­consulted, when he hath the con­trouling power of Reason allow'd him and makes no use of it, such as are called Habitual, which at first were produced by command of the Ratio­nal Part only, but through frequent repetitions at last, without any com­mand from that, out of a blind obedi­ence to a bare impulse from the Ob­ject; or lastly, such as happen when he hath altogether lost the use of it, as in Sleep or Distraction; in which last Cases 'twill be very difficult to distinguish him from a meer Machine or Automaton.

Now, from what hath been said, I cannot but think it plain, that many of the Actions before spoken of in Dr. Willis's sence, by him called Involuntary, as proceeding [Page 164]from the dominion of the Cere­bellum only, such as he calls the various Configuration of the Face, from some Impulse or Provoca­tions in the Viscera or elsewhere, erecting the Ears, turning the Neck and Eyes about, sudden Shrieks and Outcries upon some extraordinary frightful Object surprizingly affect­ing one Sense or another, furnished with either such Nerves as he sup­poses to be altogether under the command of the Cerebellum, as the fifth and seventh, or else to have a very near correspondence with that part by vertue of Vicinity, as the ninth, do more truly pro­ceed from that perceptive faculty, or (to use his own words) that part of the Soul, he hath confin'd to that part of the Medullary System called the Cerebrum. inasmuch as in reaso­nable Creatures they may and com­monly are suspended, as well as the Nerves they slow from, sometimes made use of as Instruments of Voluntary Motion by it also; and to think the contrary, is as much [Page 165]as to say, that when any body happens to express any of the afore­mention'd involuntary Acts, or but hit his Bedfellow a box of the Ear, whilst asleep, all these must be al­low'd to proceed only from the Organ of Involuntary Motions called the Cerebellum.

And of this kind also in a great mea­sure I reckon Respiration, concern­ing which I cannot easily be brought to think it satisfactorily explain'd by Dr. Willis, from the Energy of those Animal Spirits which flow only from the Cerebellum in the Par Vagum, after the same manner they do to the Heart by the Intercostal and that Pair for its pulsation, and as only under the command of the Soul, to be stopt now and then, as it pleases, by vertue of some Nerves communicated to the In­tercostal Muscles and Diaphragm, the chief Instruments of breathing, from the Spina Dorsi.

I am therefore rather enclin'd to think this Motion is of the other different kind before spoken of, un­der the Title of Instinct, proceed­ing from an extraneous superve­nient Cause, acting conformably to the course of Nature in o­other Cases of the same kind, as in Hunger and Thirst, and the like, where the obtaining the designed End or Effect renders the part from whence comes the Motion for some time insensible of the impression, and where, after the▪ ceasing of the Effect or Motion, the sense of the impression revives again, whence there happens an equal reciproca­tion between the Sense and Fruition, or Sense and Motion.

To apply this account of the manner and reason of the Spirits acting upon the Stomach and Par­ [...]te in relation to Hunger and Thirst, to that of the Systole and Dia­stole of the Lungs or Respiration, 'twill be needful to take notice, that in an Infant unborn there is no Respira­tion, but yet there is a Cerebellum; and that if this sort of Motion cal­led [Page 167] Instinct, which I make to differ from purely Natural Motions, such as are contemporary with even the first living Rudiments of the Indi­vidual, was altogether and solely owing to the Cerebellum, after the manner of that of the Heart; then of necessity the Child in the Womb ought to respire. But being satis­fied of the contrary, it remains that we account for its respiration ano­ther way, which is as afore noted, through the presence or absence of the first moving Cause or Impulse, which I make or suppose to be any thing impressing the Nerves, pro­pagated through the Organs of Breathing, so as to transmit the impression from within to the per­ceptive Faculty, presiding both over the Cerebrum and Cerebellum too, to the end the Spirits may from thence forthwith be commanded into such other Nerves as act those Muscles which serve for enlarging the whole Cavity of the Thorax, in order to let the Air into the Lungs more plentifully, which was the thing aimed at by Nature; and these [Page 168]are the Intercostal Muscles and Dia­phragm.

Now 'tis easie to conceive, that whilst the Child is enclosed in its Mothers Belly, there is not that occasion for Respiration as when 'tis born, the main Stream of Blood all that while finding no passage thro' them, and that which does by the Ruyshian Artery made of Juices much more mild and cooler, the native heat being little, and the Aliment meer Chyle or Milk; from whence it falls out that the Pulmo­ni [...]k Nerves go altogether unpro­voked, which after birth are conti­nually otherwise impressed or pro­voked by the hot Effluviums of Blood, new bred of stronger Food, and by a stronger native heat, and wholly flowing through them; which heat continually, as the Child ac­quires a greater maturity, encrea­sing, may, for ought I know, not a little contribute, by way of natural impulse, to its exclusion.

The truth of this will the more clearly appear to any who will take the pains to consider well of the structure of Parts in Children [Page 169]unborn, in whom the usual circuit of Blood through the Lungs, which are designed for rarifying and per­fecting the mixture of Blood and Chyle, is denyed; as also through the Liver, serving chiefly for sepa­rating that gross Excrement the Gall, not bred (at least in any proportion) in an Infant unborn, and in lieu of these, other Passages, (which become altogether unneces­sary after birth) provided by Nature after a shorter and more compendious way, (viz) by the Foramen Ovale betwixt the Vena Cava and Vena Pulmon. and Tubulus Arterio­sus between the Art. Pulm. and Aorta in the Lungs, and the Tubulus Venosus between the Sinus of the Porta and the Cava in the Liver; as hath been most sagaciously observ'd by the late Lear­ned Dr. Walter Needham.

'Tis true, That in several Crea­tures there are some Nerves very much depending on the Cerebellum, as are they which minister (though in a different manner, as hath alrea­dy been taken notice of, and will be hereafter further explained) to the Natural and Vital Functions, (viz.) [Page 170]the Par Vagum and Intercostal Pairs, and therefore the aforesaid Author, who is in this as in many other of his Discoveries very fortunate, and highly commendable, made a very good guess when he brought these Faculties into subjection to that part, inasmuch as by se­veral others, as well as by my own Experience upon living Bodies, we find, that notwithstanding most part of the Brain be pared off with a Razor, yea, even after the Medulla Oblongata be divided betwixt the Cerebum and Cerebellum, and taken wholly out of the Cranium, the Heart will beat, when at the same time if the Cerebellum it self be but cut in pieces, though all the rest of the Brain be kept entire, the Creature expires presently.

Yea, I have seen Respiration (which only in part depends on the Cerebel­lum) totally to cease upon only a sud­den violent compression of that part by a blow, and, after its being woun­ded, the Heart to cease beating im­mediately.

All which must of natural con­sequence fall out upon the Hypo­thesis, That those Functions of Nature do depend on the Cere­bellum for their source and in­fluence, which is constant, uninter­rupted, and out of the arbitrary jurisdiction of the Brain; yet with this difference, that in Motions purely natural, and either contem­porary with the Embrio, as the first signs of its vitality, such as is Pulsati­on of the Heart, during its enclosure within the Mother, or supervenient upon its further growth and more visible organisation of Parts, as the natural contraction of the other Viscera subservient to the offices of Protrusion of the Chyle, separation of the Glandular Juices, and proscription of the Excrements, the Animal Fluid or Spirits do alto­gether flow from the Cerebellum, the Nerves there both descending from the Cerebellum, and termina­ting in those parts afore-mentioned; whereas in Respiration, which I call a Motion of Supervenient Instinct, (if I may be allowed to use the word [Page 172] Instinct in that sence) the Nerves descending from the Cerebellum, and propagated through the Lungs from the Par Vagum, serve only to convey the first Impulse or Impression of the Object to those parts which are by Nature framed and qualified to pro­duce Respiratory Motion, and those are the Nerves of the Spinal Marrow, receiving the impression from the Cerebellum, seeing that by the aforesaid Experiment it appears plain, that af­ter the whole Cerebrum was divided from the Cerebellum and Medulla Oblongata, the act of Respiration continued for a considerable time entrire, which Motion is dependent on the Sensative Faculty presiding in the Cerebellum, transmitting the first Impulse produced by the eighth Pair or ParVagum (as before observ'd) and communicated thence to those Spinal Nerves which act the Inter­costal Muscles and Diaphragm.

So that all the office of the Par Vagum, which is propagated thro' the Lungs, is to convey the Im­pression from thence to the Cere­bellum, which by vertue of its con­nexion [Page 173]with the Caudex Medullaris (from whence the Ancients rightly thought that part had its hindermost Roots from the Cerebellum, as before taken notice of) it is able to trans­mit it further, as the Sensative Facul­ty presiding there shall direct, and that too by the common way, the Medulla Oblongata and Spinal Nerves.

And further; That this part is as capable thereof as the Cerebrum, and is not wholly and only deputed for the service of such Nerves or Or­gans as are employed by the in­voluntary part or portion of the Soul, (as Dr. Willis would have it) appears in that the third Pair of Nerves, by him allowed to be a­mongst the number of the other kind of Nerves, (viz.) those com­manded by the Will, from hence (as hath been already shewn) hath its original. And here also further­more give me leave to add, by way of conjecture, that the reason why the Soul hath not an equal command over those afore mention'd Nerves dedicated to the vital and natural Motions, is, the early date [Page 174]or commencement of the office of those Nerves, by which means they contract an habitual irresistible In­flux, much less so in those belonging to the Respiratory Functions, the exercise whereof is of a later date; and lastly, the Influx is not in the least so habitual in those other subservient to the Organical Functions of the Limbs, inasmuch as they are not capable of being exercised till a much longer time after, and then not so uninterruptedly as either the first or the second, but gradually, and with intermissions.

So that the only reason why upon cutting the Cerebellum Respiration ceases, is, that by that means its structure is discomposed, and ren­der'd unfit either to receive or transmit the impression further to the aforesaid Nerves, which are sub­servient to the Instruments of Re­spiration.

'Tis true, there arc reciprocal communications betwixt the Nerves of the Intercostal Pair, Vertebrae, and Diaphragm, yet seeing they termi­nate nor immediately in the Parts [Page 175]of each others particular distinct ju­risdictions, there is no interchangeable act or office from thence produced betwixt them.

For as, notwithstanding▪ there are so many Branches of Nerves com­municated from the Spinal Nerves subservient to voluntary motion, to the Intercostal Pair, on their descent to the Viscera, and yet by reason of their not terminating in those parts, they are not in the least able to bring these Nerves under the commands of the Rational Soul, by which provident Care of Nature it so falls out, that 'tis not in the power of any, by misguided Reason, to act injuriously to themselves: So by vertue of several Branches re­ciprocally communicated from the Intercostal Pair in its passage down to the Viscera, to the Spinal Nerves, there is no power given to them of moving the Muscles to which they are subservient uninterrupted­ly, after the meer manner of the Viscera.

But now, to return to where we left off, in some Creatures it's very plain, that Nature hath extended this imperial residence of the Soul beyond the Cerebellum, even as far as the Spinalis Medulla, having not only put this last motion, but that of Pulsation too, under the juris­diction of that elongation of the Brain; as appears in the famous Ex­periment of the Industrious Caldesi upon the Tortoise, which after the Head was cut off lived, and car­ried its Shell about, the space of six Months.

Besides which, 'tis remarkable, (by way of digression) according to another Experiment by the aforesaid Author made upon that Creature, that after even the Heart and all the Viscera besides, were taken out, except the Lungs, that Creature (to use his own Expression) was sound so to resist Death, as to turn it self from the inverted or supine position it had been placed in, in order to make the Experiment, to its prone or natural one, and to live and move six hours, after. From [Page 177]whence it appears, that Muscular Mo­tion is capable of being performed by the Animal Fluid alone, without the concurrence of the Blood, by most Authors constantly hitherto made to go a share therewith in the performance of that action. Caldesi, p. 75, 76.

So that we find Nature hath not stinted it self to one place for the Seat of the Sensative Soul, or Reservatories of the Animal Spirits so called, in order to the discharge of the afore-mention'd Functions, no more than it is at a loss about the maintaining them in their Inte­grity by other ways, when it hath so fallen out that the natural structure of the Organs, destin'd by Nature to that end, have utterly been destroy'd, of which we have many Instances in the Anatomical History, those Functions in several Creatures re­maining perfect, where after death there have been sound neither any Cerebrum or Cerebellum at all, or at least such as by their constitution was utterly render'd useless to any such end.

Of the first is an Instance of the Learned Wepfer, in a Child living sixteen hours alter it was born, and discharging all the Duties of Na­ture that one of its age was capa­ble of, and by tho by (which all the patrons of a nutritious Juice by the Nerves may do well to take no­tice of) of a very strong and good habit of Body, Misc C [...]ries. Av. 3 p. 120 whose Brain, after death, was found to be only an heap of Watery Bladders or Hy­datides, except a small part at the bottom of the Skull, lying in a Sinus made in the Wedglike Bone, where the Pituitary Gland is com­monly found consisting only of three Medullary Bodies, two of which being each of the bigness of a Kidney Bean, and the third behind them of a Pea only, from which indeed there did proceed some, but very inconsiderable Nerves, or Nervous Fibrils, but such as none can judge of a due proportion re­quisite to satisfie the Exigencies of the common natural, and vital Functions.

The truth of which is still more plain, and without exception, in another Instance in the Miscell. Med. Physic. Gallic. of a Child living sive days after it was born, Misc. Med. Phys. Gall. Au. 3. p. 54. whose Head had nothing but Water contained within the inclosures of the Dura and Pia Mater, without the least footsteps of any medullary part at all.

Parallel to which two last Instan­ces, I had one communicated to me by that curious Anatomist and learned Person Dr. Tyson, in a Child born alive, with no more Brain in the Skull than what might lye in a Filbird-shell, the Medulla Spi­nalis being much larger than ordi­nary, as though part of the absent Brain had been squeez'd down thi­ther.

Of the last ( viz. where the natu­ral conformation hath been depra­ved) there is extant an Instance in two several places of the Mi­scell. Curios. in a sat Ox, Misc. Cur. Obs. 26. & 130. An. 1. which while living there were ob­serv'd but very little signs of any such thing, whole Brain was never­theless after death found wholly petrified.

From all these 'tis manifest the Sensative Faculty is able to an­swer its internal or external Im­pressions, by one part as well as another, and that the Medullary System of the Spinalis Medulla may become as adequate a Sensory, in relation to the aforesaid Functi­ons sometimes, as either Cerebrum or Cerebellum.

And as to the power or influence the Soul in general exercises over the Nerves, howsoever different in their original, seeing we have already obser­ved what a provident care Nature hath taken for the preserving Creatures from their own violence, in that it hath not only constituted the chief Fountain from whence the great current of Spirits is derived, for the service of the vital and natural parts, by the Eighth and Intercostal Nerves, which is the Cerebellum, so as to be free from the com­mands of the Rational Will in its or­dinary way of acting, but hath also taken care that not any of those Bran­ches which have their originals from Trunks, which are under the power of voluntary dictates of the Soul, [Page 181]should terminate in such Organs by which those Functions are discharg'd, (abare communication between Nerves of different Provinces not being suffi­cient to such ends or offices, as hath been observed in those afore-mention'd additional subsidiary smaller Streams of Spirits flowing to the parts con­secrate to the natural and vital Fun­ctions by Branches propagated from the Spinal Marrow, to the Inter­costal Nerve, all the way of its descent to the lower Venter.)

So we may further also remark, that as there are some manner of Im­pressions made upon the perceptive Faculty, after such sort of a manner as that it even loses its power over its own Subjects, (viz.) the Nerves, which are subservient to its volunta­ry commands, as in Laughing, Sneezing, and libidinous Erections, the Organs by which these Actions are produc'd, being altogether under the power of those Nerves subservient to the vo­luntary dictates of the Soul, and acted after the very same manner as those of Respiration, as often as pre­portionable objects present, and (not­withstanding the assertion of Dr. Wil­lis [Page 182]to the contrary, who makes Laugh­ing proper to Man only, and, by the authority of Aristotle, Sneezing an Affection proper but to few, if any other Creature besides Man) might al­so produce the same effects in Brutes, Will p 106 provided their stupid Souls were capable of being equally impressed by such Objects as arc proper for ex­citing a rational Laughter, as we see they are by those producing the afore­mention'd venereous actions, of the want of the Plexus Cervicalis, of the Intercostal Nerves, and two or three small Branches propagated from thence to the Nerve of the Dia­phragm (which he calls a Disposition peculiar to Man, and consequently in his opinion the cause of that Af­fection in him) might be in a great measure supplied not only by that ner­vous Branch we find propagated from the interio [...]r Plexus of the Par Va­gum (which Nerve is equally depen­dent on the Cerebellum, as the Inter­costal) to the third Brachial Nerve, from which the Nerve of the Dia­phragm hath one of its originals, but also that other propagated from the Thoracick Plexus of the Inter­costal [Page 183]Nerve it self, to the same aforesaid Brachial Nerve, into which the Nerve of the Diaphragm is inserted.

So, on the contrary, there are some Impressions made upon the Soul sometimes, through which it acquires a power over those Nerves at other times in no wise subject to it, and those are the impressions either of great Joy or great Grief, suitable to which the Vital and Natural Fa­culties are made either much more or else so much less vigorous than ordinary, as even quite to languish.

How this comes to pass, accord­ing to Dr. Willis in savour of his own Hypothesis, and particularly in relation to the first, (which allows of no Involuntary Motions, but what come from the Province of the Cerebellum) is explained by suppo­sing an undulating or rowling mo­tion of the first impression upon the Brain out of it again, through the Natiform Processes into the Ce­rebellum, and from thence by the Annular Process into the Intercostal Pair of Nerves, and so to the Nerve of the Diaphragm, (and he should, to make this way of explication [Page 184]entire, have taken in also all those Vertebral Branches inserted into the Intercostal Nerve, in order to the moving of the Intercostal Muscles, without which that action cannot be performed) by a correspondence between which Nerves and those of the Face, being all of one family, the aforesaid Gesture of Laughing is per­formed.

Now, besides the needlesness of bringing the Conceptions or Im­pressions of the Brain under a ne­cessity of being executed by the in­feriour Province of the Cerebellum, till such time as 'tis proved, that such motions of the Spirits, upon extraordinary occasions, may ratio­nally be granted, without supposing a regular motion of the same through such supposed Passages lea­ding from one Part to the other at all other times, (the allowing whereof does necessarily imply a capacity of the Soul to alter the course of the Spirits influencing the vital and natural Organs, at least in some measure, at its pleasure, which is plainly contrary to Experience;) I shall hardly look upon that Hy­pothesis [Page 185]to be any more than meerly precarious.

And further, to shew, that such Effects or Alterations of the Vital Organs happening upon violent Pas­sions of the Mind, are no way owing to such a transmission of the Animal Fluid from the Cerebrum to the Cerebellum, as the aforesaid Author supposeth, I ask, how it should come to pass that in the contrary Passion of Grief, especially when occasion'd by surprizing frightful Accidents, the Heart should so languish, as sometimes wholly to cease beat­ing, seeing in the aforesaid Ex­periment we find that Motion self-sufficient, by vertue of a constant irradiation or influence of the Ce­rebellum only, and consequently could not be thought so to languish upon such occasions for want of those Spirits it never stood in need of.

Without therefore being forc'd to have recourse to that other Hy­pothesis clogg'd with so many diffi­culties, I think the aforesaid case may admit of another manner of expli­cation, consistent with what I have all-along advanc'd upon this Subject [Page 186]relating to the true source of vo­luntary and involuntary Actions: if we suppose, that from such Im­pressions upon the Soul as are ei­ther extreamly more or less wel­come to it, (in which case the Ob­ject is said to act unproportionably upon the Subject) it may not only act accordingly, above its usual irra­diation and force over the Cerebellum, and by that means, as sending the Spirits either more or less copi­ously to the Vital Organs, particu­larly the Heart, the nearest way, (viz.) by the Par Vagum and In­tercostal Pair, for that time render them more vigorous, or more lan­guid in their operations, in proportion to the difference of the Passions, just after the manner it happens in cases of Alienation of Mind or Distra­ction, where by the Strength of the Impression, or Idea upon the Mind, it drives the Spirits with such an impetus into the Limbs, as makes them act with a vast greater force than what they were wont to do, even above the resistance of Chains or Bars of Iron; but also it may transmit the Spirits more or less co­piously, [Page 187]to the Vital and Natural Fa­culties, the other way freed from the subsidiary Nerves of the Spina afore­mentioned, to the Intercostal Pair, which sends forth ramifications to the Heart (in Men especially) equally with, if not more plentifully than the Par Vagum, and from the Vertebral and Brachial to the Nerve of the Dia­phragm and Intercostal Muscles, by which means it so falls out, upon such impressions, that the Organs of Re­spiration to the sight, and that of Pulsa­tion to the touch, are very remarka­bly affected.

By this means I have endea­vour'd to restore the Brain to a capacity of putting its own Con­ceptions or Impressions made upon it into execution, without being be­holden to its neighbour the Cere­bellum, and that either in relation to its voluntary, inadvertent, or involuntary Acts; where, note, I make a distinction between Acts in­voluntary and those of inadverten­cy, inasmuch as these last, though they are not with, yet they are not contrary to the actual consent of the Will, after the manner of the natural actions of the Viscera, [Page 188]such as are out of the power of the Will to hinder; besides which, I look upon no other in Rational Creatures (in a strict sence consi­der'd) to be involuntary, foras­much as 'tis a contradiction to say a Voluntary Agent does any thing against his Rational Will (though it may be against his Approbation) by which he is only distinguish'd from a Brute: Though Dr. Willis hath all-along used the word in­voluntario in another sence, con­founding it with acts of meer Ig­norance under the term of Insciè, and those also done only inadver­tently, or without consideration, under the term of Inconsulto; and doubtless upon this notion of Invo­luntary Motions built his Hypothe­sis, which makes all those Actions which are perform'd at any time without the notice of the Intelle­ctual Faculty, notwithstanding at other times they are altogether un­der its command, equally depending on the Cerebellum as those purely na­tural, which are always free from the power of the first, and also absolute­ly subject to the last.

These Actions I have therefore called by the term of Supervenient Instinct, and being the meer Effect of external or internal Impressions upon Sensative Bodies, as Ecchoes are to those upon such as are only natural, are equally competent to Rational and Irrational Creatures, and capable of being exerted by the influence of the very same Nerves which minister to the Sensative Faculty, whether it act advertently or inadvertently in the one, or spontaneously in the other, (where, by the way, it may not be al­together unworthy of our taking no­tice, the genuine sence of that word in Actions performed by those Crea­tures, is much nearer a-kin to the term Inconsulto than Involuntario in Men) without the supposed rambling Mo­tions of Impressions made upon it, (through Passages only at some times or upon eztraordinary occasi­ons made use of) out of the Cere­brum into the Cerebellum.

Now, as to the organisation of this Part, made to consist of various Me­dullary Prominencies, Appendixes, and Tracts, by Nature contrived for and adjusted to the various functions [Page 190]of the Soul, and dispensation of the Animal Spirits thro' the whole System of the Nerves, which first are confin'd to, or made to reside in such and such places as so many distinct apartments, viz. the Commune Sensorium in one place, the Imagination and Judgment in another, and the Memory in a third; of which there is such a large and formal apparatus and description (tho' with great discrepancy of opini­on) in Willis and Vieussenius, the one placing the Commune Sensorium in his Corpora Striata only, the other in the superiour and middle Corpora Striata, jointly with the Centrum Ovale; from both whom Des Cartes and se­veral others, and with much more shew of Reason, particularly Mal­pighius, differ, Malpig. de Cereb. p 11. par. 2. placing it in the ex­tream limits of the medullary part of the Brain, where 'tis continuous with the cineritious circumassused Part; I must confess, that as I have not been able, by the best enquiry I could make either into Brains dissect­ed whilst fresh, or when boiled in Oyl, to discover any such actual con­figuration or disposition of Parts, as we find so formally delineated by ei­ther [Page 191]of them, but especially the last.

So neither do I see any necessity thereof, seeing we may much more easily, and to the self-same ends and advantages, look upon the Soul as one internal principal Sensative Facul­ty. and the whole medullary part of the Brain, as consisting of such Fibrils or Vascula's as in some places more nearly in others more remotely com­municate with the Nerves propagated thence to all the external Sensories, one adequate Common Sensory, by which that principal Faculty both re­ceives all its impressions, and accor­dingly, as by so many gradations of one and the same power, executes or performs those different Functions commonly going under the aforesaid Names of The Common Sense, or Sim­ple Apprehension, Imagination, Judg­ment, and Memory.

And as to the second, (viz.) the Medullary Tracts, by which the Animal Fluid, as by so many Rivu­lets, is derived from the great Pond or Magazine into many Rivers, fur­nishing the whole Body therewith, all I could find by the most diligent [Page 192]search, were only those which have already in the preceding Sheets been remark'd, of which, in the first place, are those in the Corpora Striata, very large and discernable.

Those in the inward or concave Superficies of the Corpus Callosum running transversely by the Sep­tum Lucidum into the Fornix, and from that longitudinally into its hinder Thighs or Pillars former­ly called Bombyces, over which they run in a wreathed manner, as was before observed, terminating in the back part of the Lateral Ventri­cles, enclosed in the hinder Limbs of the Brain, which Ventricles at length terminate in, and are con­tinuous to the subjacent fore-part of the Crura Medulla Oblongata.

Those in the Thalami Nervorum Opticorum running obliquely down to part of the subjacent Crura and Caudex Medullaris.

Those of the Nates and Testes run­ning after the same manner, and ter­minating so too, only something lower.

Those in the Annulary Process, which forasmuch as they have ne­ver before been taken notice of, I have caused to be engraved in a Figure by themselves, whose Me­dullary Tracts or Striae, furnished with Spirits both from the continuous medullary Caudex, and Productions of the Cerebellum too, of which the An­nular Process is made, (by means whereof the Nerves appertaining thereto may be rationally supposed to be under the influence of both those Parts, conformable to what hath all-along been asserted;) are as visible, being more thick, and of a far harder consistence, than that of the Corpora Striata themselves, (tho' upon every attempt of cutting that Process, they may not appear so) and most of them terminating in a mid­dle Medullary Tract, by means whereof there is the same inconve­niency prevented, at least in some measure, as there is by that sepimen­tum of the Pia Mater, continued from the joyning together of the Crura Medulla Oblongata, down quite thro' the Medulla Spinalis, (viz.) that at the same time the Nerves on one side [Page 194]may, (as Molinetti, Mol. p. 104 tho' in another place of the Brain, hath truly obser­ved) by any morbid cause, be in­jured, those on the other may e­scape.

Concerning these, seeing they seem to have a particular aspect or relation to those Nerves, whose originals we find nearest them, it may not be unreasonable to think they are particular Conduits, from whence the said Nerves are fur­nished with Animal Fluid, though at the same time we must allow a very free communication betwixt them all.

And consequently, we may sup­pose the first of those to con­vey Spirits from the globous me­dullary part of the Brain next to it, by Vienssenius called the Supe­riou [...]. Part of the Centrum Ovale, down to the subjacent medullary part of the Brain, to augment those which are produced lower, and par­ticularly for the service of the Olfactory and Visory Nerves, which last hath more eminently its Sup­ply from the Thalami Nervorum Op­ticorum.

The second sort, or the trans­verse Striae's of the Corpus Callo­sum, to convey an additional Sup­plement by way of the wreathed Tracts in the hinder Columns of the Fornix, to the Crura Medulla Oblongata, where they become con­tinuous to the reflex'd part of the Lateral Ventricles backwardly, for the service also of the aforesaid two Pair of Nerves, but more par­ticularly to those arising lower ei­ther on the Annular Process or Cau­dex Medullaris.

Those of the Thalami Nervorum Opticorum and Natiform Processes, the first of which lies upon, and is continuous to the subjacent medul­lary part of the Crura Medulla Oblongata, the other to the Cau­dex Medullaris, may be supposed to derive Spirits on the behalf of those Nerves which spring from any adjacent parts, whether on this or the other side of the Annular Process or Caudex Medullaris.

And of this sort are the Optick Nerves, which are supplied imme­diately from the first of those Me­dullary Prominencies, and not un­likely from those fair Medullary Tracts afore-mentioned, running from the Root of the Fornix, extending themselves all the way between the Corpora Striata and Thalami Nervo­rum Opticorum, in which last at length they are obliterate. The Third, Fifth, Sixth, and First or hard Branch of the Auditory Nerves, mediately by continuity of them with the Annular Protuberance, to all which the other or lesser Me­dullary Prominencies called Nates, by vertue of their continuity with the subjacent parts, may be sup­posed to contribute something al­so: and these seems to be better pro­vided for than the rest of the Nerves, inasmuch as besides this way of being supplied from the Cerebrum, they have also another very visible, and much larger, from the Second Process of the Cere­bellum, of which the Annular Pro­tuberance [Page 197]is made, and this see­mingly not without a provident Design of Nature, seeing the Nerves which are derived thence are much larger, and have a greater Task of service layed upon them than any others of the whole Brain, as hath also the Par Vagum, or eighth Pair, which therefore, by vertue of its insertion between the Chordal or third Process of the Cerebellum and Corpus Olivare (and not according to Dr. Willis, from the points or extre­mities of the Corpora Pyramidalia) hath a double tribute of Spirits, one from the Caudex Medullaris or Cere­brum, the other from the Cerebel­lum.

And to this End or great Ser­vice it looks as though this Process was furnished with such a Texture as it appears to have, of strong, large, medullary Striae's, capable of receiving and containing a Supply from both Fountains.

Whence it may not be unseaso­nable to remark, That not without shew of good Reason I have all-along asserted the Propriety of the Brain to those Nerves in part, al­lowed by Dr. Willis to be no fur­ther affected by any Impressions of the Brain, than as first con­veyed from it into the Province of the Cerebellum, and consequent­ly to depend immediately on this last for influence entirely in order to convey Animal Spirits to those parts wherein they are inserted.

Upon the Caudex Medullaris, on its under side contiguous to the hinder Extremities of the Annular Process, are situate the Corpora Pyramidalia and Olivaria, over-against which are the two long Medullary Tracts lately taken no­tice of, seeming to come from the transverse Medullary Process behind the Testes, and terminating in those other transverse Medullary Processes before the entrance into the Fourth Ventricle on the other [Page 199]side, by which there may be con­veyed a considerable Portion of the Animal Fluid to the Pathetick Nerve, which hath its rise from the first transverse Process, and to the soft or second Branch of the Auditory Nerve, which hath its rise from the second on that side, and also to the Ninth and Tenth Pair on the other side.

And to conclude, From all these taken together, with the rest of the whole medullary part of the Brain, the Overplus of what is not spent upon the inmate Nerves of the Brain may truly be supposed to be promiscuously dispensed to all those other extraneous ones produced from the elongation of the Brain, call'd the Spinal Marrow. In which last there is this conformation or disposition of Parts differing from that of the Brain, that whereas in that the cineritious part is external, 'tis here internal; and this for very good reason, and by a provident contrivance of Na­ture, seeing that not only the cine­ritious part of the Brain serves for [Page 200]supplying those Nerves which have their original thence, as well as all the rest of the Spinal Marrow, and con­sequently ought to have the lar­gest space and dimensions possible, which without this situation could not have been; but also without this contrivance the Nerves of this part must of necessity have had their ori­ginals from the cineritious part of the aforesaid Marrow, contrary to both the custom and convenience of Na­ture too.

• A A The fore Lobes of the Brain.
• B B The hinder Lobes.
• CC The Cerebellum.
• D D The lateral Sinus's.
• E E The Vertebral Arteries as they pass between the first Vertebra and the Bone of the Occiput.
• F The Vertebral Sinus.
• G, &c The Dura Mater on the right side taken off from the Spinal Marrow, and remaining on the left.
• 1, 2, 3 4, &c. The ten pair of Nerves belonging to the Brain, with seven of the Spinal Marrow.
• a The Foramen that opens into the Pituitary Gland from the Infundibulum.
• b b The two white Protuberances behind the Infundi­bulum.
• c c The two Trunks of the Carotid Artery cut off where they begin to run betwixt the fore and hinder Lobes of the Brain.
• d d The two Arteries joyning the Carotids with the Cer­vical Artery, called the Communicant Branches.
• e e Two large Branches of the Cervical Artery, some­times seeming as tho' they came from the Com­municant Branch on each side, from the first of which the Plexus Chorocides hath its original in chief, and from the last the Plexus Chorocides of the 4th Ventricle.
• f Several little Branches arising from the Carotid Artery.
• g The Cervical Artery composed of the two Trunks of the Vertebral Artery within the Cranium.
• [Page]h h The two Trunks of the Vertebral Artery.
• i i i The Spinal Artery.
• k A small Branch of an Artery running through the 9th pair, broken off from its other part thro' inad­vertency of the Graver.
• l l The Crura of the Medulla Oblongata.
• m m The Annular Protuberance, or Pons Varolii.
• n That part of the Caudex Medullaris on the right side called by Willis and Vieussenius Corpora Pyra­midalia.
• o That part on the same side called Corpus Olivare.
• p The foremost Branch of the Carotid Artery, divi­ding the fore Lobes of the Brain, consisting of two Branches, one of them only appearing here.
• q q Little Branches of Arteries helping to make the Plexus chorocides in the 4th Ventricle.
• r r r Branches of Arteries dispersed from the Cervical Artery upon and thro' the Annular Protuberance.
• s s Part of the 2d Process, or Podunculi, of the Cerebellum.
• * * The Spinal Accessory Nerve.

• A A The Edges of the Skull.
• B B The Dura Mater upon the bottom of the Skull.
• C C The lateral Sinus's
• d d The superiour, longer and narrower Sinus's.
• e e The inferiour, shorter and wider Sinus's.
• f The Process of the Bone Cribriforme, called Crista Galli.
• g g Some small descending Branches of Veins upon the bottom of the Dura Mater.
• h h The first Branch of Arteries proper to the D. Mater.
• i i The second Branch of Arteries belonging to the Dura Mater.
• k The third Branch belonging to the Dura Mater.
• L The last hole of the Skull.
• m m Several Veins communicating with the inferiour short Sinus's.
• n Part of the Os Jugale.
• o o The Os Ethmoeid, where the first pair of Nerves or mammillary Processes go forth.
• p p The Optick Nerves cut off.
• q q The Carotid Arteries cut off.
• r The third pair of Nerves vissible only on one side.
• S S The fourth pair of Nerves turned up.
• t t The fifth pair of Nerves on one side expanded be­fore it is divided into its three Branches, on the other side whole; which Nerves, with its three Branches, are expressed in the third Figure.
• V Its foremost superiour Branch on the left side, going out at the second hole of the Skull.
• w The sixth pair of Nerves.
• [Page]X The Intercostal Nerves, in this subject proceeding from two Branches of the fifth Nerve, joyning with the body of the sixth Nerve.
• y Two Branches of the fifth pair of Nerves, in this subject running almost close to the 6th pair, being partly the Roots of the Intercostal Nerve, which creeps out of the Skull under and between the Coats of the Carotid Artery.
• z z The Body of the Carotid Artery, after it has entred the Cranium.
• 1 1 The Glandula Pituitaria.
• 2 2 The Circular Sinus.
• 3 The Infundibulum.
• 4 4 The Frontal Arteries.
• 5 The place where the Lateral Sinus's begin to be declive and tortuous.
• 6 The Dura Mater raised and reclined to shew the subjacent Nerves.
• 7 7 The seventh or Auditory Nerves.
• 8 8 The eighth pair, or Par Vagum.
• 9 9 The ninth pair.

• A Its Trunk.
• B Its Ganglion.
• C Its first or superiour Branch, going out at the second hole of the Cranium.
• D Its second or midle Branch, going out at the second hole.
• E Its third or hindermost Branch, going out at the fifth hole.

• A A The third or longitudinal Sinus.
• B B The first and second, or lateral Sinus's.
• C The fourth Sinus.
• d d d A Vein running on each side of the third Sinus.
• eeee Mouths of Veins opening into the longitudinal Sinus of the Dura Mater, after a contrary man­ner one to the other.
• f f The fifth Sinus at the bottom of the Falx.
• g The Torcular, where all the superiour and lateral Sinus's meet.
• h h The tortuous part of the lateral Sinus running un­der the Cerebellum.
• i i The Veins entering the fourth Sinus from the Plexus Choroeides.
• k The place where the fourth Sinus arises.
• * * The Specus or round hole at which the lateral Si­nus's on each side go out into the internal Jugu­lar Vein.
• l l Two large Veins, whereof one enters the fourth Sinus upon the second Process of the Dura Ma­ter, so as to resist the course of the Blood in that Sinus, in its ascent to the Torcular; the other upon the same Process, so as to hinder its descent to the Internal Jugular, contrary to a conforma­tion of Vessels which Vieussenius mentions in his third Table, H H.
• mmm Transverse Chordal Ligaments in the longitudinal and lateral Sinus's.
• n n Part of the Dura Mater on each side of the longitu­dinal Sinus.
• o o Portions of the Pia Mater.
• PP &c Divers small Veins on the Dura Mater, which en­ter those that run on the sides of the longitudi­nal Sinus, according to its length.
• [Page]qq &c The Veins of the Cerebrum as they appear under the Pia Mater, before they enter the longitudi­nal Sinus.
• R R The falcated Process, with its Veins which enter the fifth Sinus.
• S S The second Process of the Dura Mater.
• † † The beginnings of the Jugular Veins.

• A A The Fornix cut off at its Roots and turned back.
• b b Its Roots at the beginning of the Thalami Nervo­rum Opticorum.
• cc, &c. The Thalami Nervorum Opticorum.
• d d That part of the Crura Fornicis which growing somewhat thicker as it turns off towards the La­teral Ventricles, runs over the Crura Medulla Oblongata, which being very prominent in Sheep, and Calves, helps to thrust it up into such a Protuberance as the Ancients called Bombyces or Hyppocampi.
• e e That part of the Plexus Choroeides which is made of the first Branch of the Cervical Artery, some­times seeming as tho it came from the Commu­nicant Branch▪ in the Lateral Ventricles.
• f The place where those two Plexus's on each side meet under the Fornix.
• g g That other part of the Plexus which is made of the second Branch of the Cervical Artery joyned with the first by a Communicant Branch not to be seen here, lying under the Crura Fornicis, which is expanded all over the Isthmus, becom­ing glandulous near to, and especially under the [...]a [...]d [...]la Pinealis covered here with the Fornix.
• [Page]h h Two large Veins coming from the top of the up­per part of the Plexus down to the other Branch of the Plexus, all the length of the third Ventri­cle, and then terminates in the the fourth Sinus.
• i i The Trunks of several Arteries, appearing as they were cut off in dividing the Medullary † and Cineritious * part of the Brain.
• k k A Venous Branch of each side entring the Plexus Choroeides, from whence there are many slips branched upon the Corpora Striata.
• Δ Δ The Corpora Striata whole.
• l The Rima of the third Ventricle.
• m m A long Medullary Tract between the Thalami Nervorum Opticorum and Corpora Striata.
• nn, &c. The Centrum Ovale of Vieussenius.
• O The fourth Sinus of the Dur. Mater.
• P The Torcular, where the four, and sometimes five, Sinus's meet.
• Q Q The Lateral Sinus's.
• R A large Vein entering the Lat. Sinus's on one side.
• SS, &c. The Cerebellum covered with the second Process of the Dura Mater on its uppermost part,
• T T The Vertebral Arteries.
• V V the Vertebral Sinus's.
• W The Medulla Spinalis, with its integuments.
• x x The Style supporting the large Veins of the Plexus Choroeides in the third Ventricle.
• q q The Lymphaeducts of the Plexus Choroeides.
• Y Y Two of the Cervical Nerves springing from the Medulla Oblongata.
• ††, &c. The Medullary part of the Brain.
• **, &c. The Cineritious part.

• A A The Crura Medulla Oblongata.
• B B The Annular Process, or Pons Varolii divided.
• c c The Transverse Striae.
• e e The intervening Medullary Tract in which the Striae terminates on each side.
• f f The third or chordal Process of Dr. Willis.
• h The Spinal Marrow.
• i i Some part of the Cerebellum.
• k k The second Processes of the Cerebellum, which com­pose the Annular Protuberance.
• l l The cineritious part of the Medulla Oblongata.

• A A The Cerebellum.
• B B The arboreous ramification of the Meditallium of the Cerebellum appearing, being cut right downwards.
• C C The Pathetick Nerves.
• c c The Nates.
• d d The Testes.
• e The transverse Process whence the Pathetick Pair have their original.
• f The Glandula Pinealis.
• g g The first Process of the Cerebellum, running from it to the Nates here extended laterally.
• h h The third or Chordal Processes.
• i i The transverse medullary Process in the 4 Vent. from whence the soft Branch of the 7 N. has it original.
• k k The Medullary Process descending from the Trans­verse Process behind the Testes, down to the afore­mention'd other Medullary Transverse Process.
• l l The Originals of that Process a little too low.
• m m The eighth pair of Nerves.
• n The Calamus Script▪ or Extremity of the 4th Ventricle
• o The Spinal Marrow.
• P P The Accessory Nerves.
• q q The tenth pair of Nerves.