The remaining medical works of that famous and renowned physician Dr. Thomas Willis ...: Viz I. Of fermentation, II. Of feavours, III. Of urines, IV. Of the ascension of the bloud, V. Of musculary motion, VI. Of the anatomy of the brain, VII. Of the description and uses of the nerves, VIII. Of convulsive diseases : the first part, though last published, with large alphabetical tables for the whole, and an index ... : with eighteen copper plates / Englished by S.P. esq.

CHAP. XVIII. Of the relation or mutual respect of either Appendix of the Cerebel, to wit, of the anterior, which are the orbicular Prominences; and the posterior, viz. the Annular Protuberance: Also of the remaining portion of the oblong Marrow continued into the Spinal Marrow.

BEsides the aforesaid Nerves, to wit, the fourth, fifth, sixth, seventh, and eighth pair which are imployed for the performing the tacit Edicts of the Ce∣rebel for every involuntary Function, and those equal in number to the rest subject to the Brain, that cause the Cerebel to have an Empire divided with it; there are also some Processes and Protuberances, which being placed before and behind the Cerebel, are its Appendixes, that are taken into part of the same Office and Ministry. The description and use of these, are already particularly delivered. But for that (as a while since we intimated) there happens a certain respect or habit between the orbicular Prominences, which is the anterior Appendix of the Cerebel, and the an∣nular Protuberance, which is the other posterior Appendix of the same, and that one part is proportionate to the magnitude of the other; so as when the natiform Prominences are greater or greatest, the annular Protuberance is always smaller or smallest; and on the contrary, they who have this latter in a very great bulk, in them the other is lesser; and so for that either part seems to be a peculiar Repository of the Spirits, which belong to the oeconomy of the Cerebel, when a greater provision of them is laid up in one Store-house, therefore there resides a lesser in the other; when I say there is this kind of constant relation found between these parts, it yet remains for us to find out for what end this is so constituted.

Seeing that the animal Spirits are disposed within the several parts of the Head in distinct Schemes of Rays, through which are variously transmitted, as through Per∣spective-glasses, the impressions of sensible things and the instincts of motions to be performed; it easily occurs, that there are commerces had this way and that way in the natiform Prominences between the Brain and Cerebel; and that the Spirits in∣habiting the annular Protuberance are Inter nuncii or Messengers going between, which transfer the mutual respects of the Praecordia and Viscera, as also of the parts that are wont to be pathetically moved. But if it be inquired into, what kind of commerces and respects those are which the Brain carries to the Cerebel, and on the contrary, and that either have to the Organs of the vital and merely natural Function, we shall in so difficult and very intricate a matter propose our Opinion, though with an hesi∣tating and doubtful mind.

We have before intimated, that the orbicular Prominences did deliver to the Ce∣rebel the forces of the Passions to be carried from the Brain to the Praecordia, and did receive from it, and communicate to the Brain the necessities of the natural Instincts delivered from the Praecordia and Viscera to the Cerebel. To these moreover we add, that the annular Protuberance serves wholly for the same offices, though after ano∣ther manner; to wit, this receives the forces of the Passions, as it were at a second hand, from the Deputiship of the Cerebel, and transfers them then immediately to

the Praecordia; and this seems to be the chiefest office of this part. Further, the same Ring receives immediately the natural Instincts from the Viscera of the middle and lowest Belly, and impresses them on the Cerebel to be conveyed further to the Brain; which kind of use it exhibits secondarily by affording only a way of passage: For indeed such Instincts having past through the Cerebel, we suppose to be formed and perfected within the orbicular Prominences, from whence being transmitted into the Brain, they draw forth requisite actions without the previous knowledge of it, or intention of doing.

Hence it may be supposed, that the annular Protuberance contains chiefly the ani∣mal Spirits which perform the intestine commotions of the Affections. In every vio∣lent passion of the Soul, presently the Praecordia are greatly troubled, to wit, the same being variously drawn together or spread abroad, compel the blood into divers fluctuations; but indeed a great company of the Spirits, somewhere got together and ready for Excursions in a set Battel, do perform these disorders and irregular motions of the Praecordia; and for that the Spirits can be disposed for this in no other part than here, before the beginnings of the Nerves, constituted for these offices; therefore this Protuberance in a man, by reason of the ragings of the Passions to be performed by a certain force and incitation, is far greater than in any other Animal. For as he is wont to be suddenly and vehemently disturbed, therefore the Promptua∣ry or Store-house is required to be more large, in which a greater plenty of Spirits may be kept, to be bestowed on such inordinations of the Affections. Next to a man this part is greatest in a Dog, Cat, and Fox; in a Calf, Sheep, Goat, Hare, and other milder Animals it is very small.

But as the annular Protuberance seems to be the chief Organ or Chest of the Spi∣rits, from whence the winds of the Passions, destinated for the exciting the Praecordia, are conveyed into the breast; so we suppose the orbicular Prominences to be a means of passage, and the very instruments whereby the instincts and necessities of the Prae∣cordia and Viscera are communicated from the Cerebel to the Brain. Yea, the ani∣mal Spirits dwelling in this, as a retiring place, do not only transmit these kind of Ideas or formal Reasons of the Instincts, but in some measure form and prepare them for the Brain. For when as some brute Animals, whose Brain is not imbued with a previous knowledge or practical habits, chuse and bring forth some spontaneous actions as it were with judgment and deliberation, certainly we may believe the in∣tentions of these kind of acts are suggested from some other place than the Brain, to wit, from the aforesaid Prominences. Wherefore 'tis to be observed, that in some Brutes endued with an indocil or dull Brain, the Buttock-like Prominences are greatest, as may be seen in a Calf, Sheep, Hog, and many others; which Animals, as soon as they are brought to light, presently seek for their food, and what is con∣gruous for them they readily know. But in a Man, a Dog, Fox, and the like, who are more apt to learn and acquire habits, these Prominences are very small; and these Animals being newly born, are furnished only with a rude and imperfect sense; besides, they are found wholly unapt to seek out their food. Upon this Observation (which holds good in most Animals which I have yet happened to dissect) as upon a Basis or foundation I dare build this kind of abstruse Hypothesis concerning the natural Instincts and Affections of the Praecordia. For as the living Creatures which are more strong in instinct, as Sheep, Hogs, Oxen, Goats, and other slow and gentler beasts, that are not obnoxious to Passions, are also less docile or apt to learn; and on the contrary, they in whom the Affections are wont to predominate, and who are furnished with a certain wit, (as besides Man, are Dogs, Foxes, and some other hotter Animals) are less powerful in Instinct: and as I have observed in the frequent Dissection of all sorts of Heads, that in those kind of living Creatures, who live rather by Wit than Instinct, the annular Protuberance, placed below the Cerebel, was notedly great, and the orbicular Prominences only very small; but in other living Creatures, where the Instinct exceeded the wit, and who were less prone to strong Affections, the orbicular Prominences were very great, and on the contrary, the ringy Protuberance exceeding small: From hence I was forced to think, that the or∣bicular or natiform Prominences, where they are great, are instead of another or supplementory Brain, and the chief Organs of the natural Instincts; yet so, as these parts also serve for a way or means of passage for the transferring the Passions from the Brain towards the Cerebel and Praecordia; and that (as we have already hinted) the greater existency of the annular Protuberance is to contain plenty of Spirits re∣quisite

for the winds of the Passions; yet in the mean time, by a further tending forwards or declination of the Spirits inhabiting this, the Species of the natural In∣stincts, being sent from the Praecordia and Viscera, pass through. But however the business is, because nothing can be certainly affirmed, or by demonstration, if this our Opinion please not others, at least it may be pardoned.

There remains not much more to be spoken concerning the Offices and Uses of the Cerebel and its Appendix. Concerning its substance, there is something more worthy taking notice of, to wit, that it very much differs in this respect from the structure of the Brain also, for that its cortical little circles are not founded in the stretched out Marrow, as the convolutions of the Brain; but being deeply cut in, are discontinued in their whole tract: so that the whole System of the Cerebel is as it were a cluster of Grapes compacted closely together; in which, although the Berries be contiguous, yet they remain distinct one from another, and bring forth fissures through the whole thickness of the mass. Yea the outward superficies of the Cerebel consists as it were of very many Tubercles or little Tad-stoles or Puffs which grow together on little stalks; and those stalks pass into greater branches, and they at length being bipartite or twofold, go together into two larger Marrows near the bottom of the Cerebel, in either of which are three distinct medullary Processes: of which threefold processes on either side we have already spoken. But of these con∣cerning the use of the Cerebel in general, we shall yet further advertise you, that as very much of its substance is cortical, it begets animal Spirits in great plenty, to which in the circulating there is not granted, as in the Brain, an equally great space; for that there seems not to be much need of it in the animal Government. For the Spirits so produced in the Cerebel plentifully by a perpetual emanation, ought to flow outwardly for the offices of the natural and vital Function: but more inwardly for the impulses variously sent into them, they admit certain undulations or wavings, by which some occasional acts of the involuntary Function are brought forth, as is shewn before.

But as it is manifest enough, that the animal Spirits are generated within the cor∣tical little circles of the Cerebel, it doth not seem needful that we should ordain their Work-house in the Ventricle subject to its frame. For that Cavity (as we have already shewn) is only an empty space, which lying under its double little foot and medullar Trunk, comes between it and the overlying bunching out of the Cerebel. But indeed there belongs to this besides a certain use, to wit, that the serous watry heap laid aside out of the Glandula's and infoldings of the Vessels, as also from the substance of the Cerebel, being made over-moist, distilling down, might slide into this Cistern. From whence, lest it should flow down upon the beginnings of the Nerves, by a restraining Membrane it is compelled into the hole of the strait Den lying under the orbicular Prominences; and from thence is received from the decli∣ning aperture of the Tunnel, and carried out.

Below the Cerebel, the oblong Marrow going forward with the rest of its tract even to the hole of the hinder part of the Head, ends at length in the spinal Marrow: but in its Trunk, as yet contained within the Skull, besides the Nerves and Processes but now recited, the beginnings of the ninth and tenth pair of Nerves are also radi∣cated. Of which there will be hereafter a proper place to speak, when we shall in∣stitute the whole Neurology or the Doctrine of the Nerves. In the mean time, we shall take notice of the beginning of the ninth pair, which is peculiar in Man, and different from what is found in Brutes: To wit, in Man below the origine of the eighth pair, a certain Protuberance grows to either side of the oblong Marrow. Out of that four or five distinct Fibres do come forth; one or two of which binds about the Vertebral Artery passing through it, but all grow together into the same Trunk, which is the Nerve of the aforesaid pair. This Protuberance, the Pia Mater being pulled away, may be easily seen, and seems to be the Repository or Store-house of the Spirits destinated to this Nerve.

For as this Nerve is bestowed on the Tongue and its Muscles, and so conduces chiefly to the performing of speech in Man, who hath a greater and more frequent use and exercise of the voice, there seems to be need of a great provision of Spirits, plenty of which ought always to be in a readiness. But in Brutes, who have none, or a rarer necessity of the voice, such a Protuberance is wanting, because it is not required in them that the Spirits should be gathered together by heaps, as it were in a certain Porch, before the Organs of the Voice, but that it may suffice for them to

be called forth by degrees out of the common tract of the oblong Marrow. Further, whereas some fibres of this Nerve bind about either Vertebral Artery, unless I am de∣ceived, that is so ordained for this end, lest perhaps in speaking, when at any time we are more vehemently moved, the blood being stirred up, might rush upon the Brain with a torrent. For this Nerve binding about the Vertebral Artery, as it were with a bridle, and so as a Moderator not only of the Tongue, but also of the Blood, restrains its more rapid influence. After the same manner, and for no other ends, do the recurrent Nerves, destinated to some part of the same office, variously bind about the Trunk of the great Artery, as shall be shewn afterwards.

As soon as this inferior portion of the oblong Marrow is uncloathed from the Pia Mater, the pyramidal bodies come in view otherwise lying hid. These in all Ani∣mals, endued with the annular Protuberance, are constantly found; also as that Protuberance is bigger, so these bodies appear more noted: but indeed in a Man and a Dog they seem like two large Nerves, which being produced out of that Ring, end over against where the eighth pair arise in sharp points. If the use of these be sought into, it is most likely, that the animal Spirits superabounding in the annular provision or store, do flow out as it were by these Emissaries, which Spirits however run into the beginnings of the eighth pair placed near, and so are bestowed by their proper means on the offices of the involuntary Function.

Although the oblong Marrow retains not its name beyond the limits of the Skull; yet it is the same substance, which from thence being continued further into the cavity and utmost recesses of the whole Spine or Back-bone, is called the Spinal Mar∣row: but it is brought forth for this, that the Nerves to be distributed into the Limbs and Members more remote from the Head, might more commodiously arise out of the same medullar substance stretched out into the neighbourhood of every part. In∣deed all this whole medullar Trunk, which is continued from the bottom of the Brain even to the Os sacrum, seems like the Pneumatick Chest, or Bellows of a pair of Or∣gans, which includes the blast or breath destinated to every Pipe; for in like manner the animal Spirits are contained in this marrowy tract, which blow up and actuate all the Nerves hanging thereto, as occasion serves.

If you behold the origine of the whole, it seems that the whole frame both of this oblong Marrow and the spinal, is of a medullar or marrowy substance, every where growing dispersedly through the Brain and Cerebel, and then being gathered more round together in the middle of either, becomes as one heap. For the Marrows besmearing all their folds and turnings about, are as so many little rivers, which springing from thence, begin to be congregated in the middle, and to be poured out in one great one; but being from thence united, they make the oblong Marrow, as it were the chanel of the Sea, big enough for the motion or ebbing and flowing and reciprocation of the animal Spirits: which belly or chanel, however stretching it self further beyond the Skull, is increased into the spinal Marrow, as it were the bosom or process of the former.

But as the medullar tracts, besmearing the folds and convolutions of the Brain and Cerebel, unfold themselves into their middle Marrows and medullar Trunk, and so the Spirits springing dispersedly from their first fountains, congregate as it were into a certain diffused Sea; so from this Sea, causing an ebbing and flowing, or a con∣tinual or very frequent influence of the animal Spirit, the same Spirits flow out into the depending chanels of the nervous System.

Concerning this part of this Marrow, which being included in the long bosom or chanel of the Vertebrae or Back-bone, and according to all their joyntings, being mark∣ed with as it were knotty processes, is called the Spinal, there occur not many things worthy consideration, besides what are commonly known. The figure, situation, as also the body of this, in its whole tract, are known generally to be cloven in two, not only by Anatomists, but by every Butcher. The ramifications or branchings of the Nerves, proceeding from the spinal Marrow, are delivered hereafter. Concer∣ning its conformation something peculiar occurs. For as the spinal Marrow is as it were the common passage or chanel of the Spirits flowing out of the Head into the Nerves, it may be observed, that this chanel, not after the usual manner of other passages, where many rivers flow in, doth swell up more; but on the contrary, in what place it hath more and greater Emissaries, its magnitude is increased; for in those parts of the spinal Marrow, out of which the brachial and crural Nerves arise, (or those Nerves belonging to the Arms and Legs, whose beginnings are more and larger)

its Trunk becomes much thicker than in the rest of the frame or substance. The reason of this is, because within the medullar tracts the animal Spirits run not, nor pass through with so swift a passage, but for the most part flowing leisurely from their Fountains, when they have filled the whole space, they stay therein; and as many Spirits, upon occasion offered, are wont to be bestowed on every work, those remaining there in readiness frame certain convenient Promptuaries where they may divert themselves. Wherefore we ordinarily observe, not only of this Marrow, but of the Nerves themselves, that as often as a small branch is distributed into many shoots or suckers to be sent forth here and there, always in the very knot of the division there grows a far greater fold than in the rest of the Trunk of the Nerve; so that 'tis a wonder from whence the Nerve should acquire so in the middle of its passage a new substance and more ample bulk. But of these things and others belonging to the Doctrine of the Nerves, it behoves us to discourse in the following Chapters.