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. V. The Brains of Fowls and Fishes described.

WHat hitherto we have shewn concerning the description of the Brain and its Appendix, we chiefly owe to the observations made of the dissection of the Heads of a Man and of four-footed Beasts. We shall now proceed to the commenting upon these Observations; to wit, that we may endeavour, from the fabrick rightly considered of the parts of the Brain, so described, to erect their offices and uses, and so to design the government of the animal Function: But because a compared Anatomy may yield us a more full and exact Physiology of the Use of Parts; therefore before I enter upon this task, it will seem worth our labour to in∣quire into the Heads of some other Animals, to wit, of Fowls and Fishes.

We have already hinted, that the Brains of Men and of four-footed Beasts, were alike in most things; and also that the contents in the Heads of Fowls and Fishes being far different from both the former, yet as to the chief parts of the Head, are found to have between themselves an agreement. The kinds of either Animals being coetaneous, and as it were Twins from the Creation of the World, do testifie their affinity in nothing more than in the fabrick of the Brain. That it is so in Man and four-footed Beasts plainly appears already: we shall now see if that the Anatomy of Fowls and Fishes will shew us any thing worthy of note.

That we may begin with Fowls; the covering of the Skull being taken off, the hard Meninx or Membrane embraces strictly the bulk or mole contained within. In the midst of it, where the brain is divided into two Hemispheres, it hath a bosom stretched out at length, which notwithstanding, no Falx (or Scythe) being let down between the interstices, is inserted less deeply in the brain: then, where this Mem∣brane distinguishes between the brain and the Cerebel, two lateral bosoms are for∣med. Besides, in Fowls there is a fourth bosom, which hath its place a little more backward than in a man or four-footed beasts; for a little below the pineal Kernel a hollow and smooth process of the hard Meninx is sent down upon the shanks of the oblong marrow, where presently it is divided into two branches, on either side where∣of it sends forth one upwards into the cavity between the streaked Membrane and

[illustration] interior base of a calf skull

Fig: VI^a

the Hemisphere of the brain, planted in the hinder part of the brain.

This superior Membrane or hard Meninx being cut off, and separated round about the Pia Mater, appears very thin, which is not, as in man or other perfect Crea∣tures, marked with such frequent infoldings of the Vessels; but this most subtil Me∣ninx being made of a texture of Fibres, only clothes, and every where intimately binds about the even and plain superficies of the brain contained within, and wholly destitute of turnings and windings about.

The fabrick of the brain in Fowls is otherwise than in man or four-footed beasts: for besides that in its compass the inequalities and the turnings and windings are wholly wanting; also more inwardly, the callous body and the Fornix, as also the chamfered bodies, which we described before, are all lacking: and besides, the sub∣stance of the brain it self is figured after another manner. That these may the bet∣ter be beheld, make the dissection of the brain of a Goose or a Turky-Cock; and the Membranes being cut off, by pressing lightly the fissure or cleft of the brain, you may divide the middle of it one from another, and go forward to separate it, till you come to its bosom, in which place are two marrowy bodies, which being stretched out like Nerves, connect the Hemispheres one to another. Either side of the Inter∣stitium or the space between, is clothed with a whitish Membrane, which is marked with streaks or beams, lying or running from the whole compass or circumference, to the lower corner; and these streaks concenter about the insertions of the medul∣lary bodies. Then, if this Membrane be cut, in either Hemisphere of the brain, there will appear underneath a cavity, which goes under the whole space, from the side of the Interstitium, and for a great part, the hinder region of the brain, and is arched or chambered with that streaked Membrane. Either cavity or hollowness, about the bottom, is opened into an intermediate or common passage, which lies open to the Tunnel; and from either side of this passage the shanks of the oblong marrow are stretched out, to which, on either side, the Hemisphere of the brain is hung by two medullary bodies; to wit, one marrowy or medullary body goes out from the mole or substance of the brain lying under the Ventricle, the other from the streaked Mem∣brane covering the Ventricle. From these two, placed on either side, the medullary bodies being stretched out cross-wise, like Nerves, joyn the two Hemispheres of the brain to one another. Besides, these two growing together on either side, fix either Hemisphere of the brain to the shanks of the oblong marrow.

So the figure of the Brain in Fowl, if you compare it with the brain in men and of the more perfect four-footed beasts, seems to be as it were inversed. For as in these the Cortical part is outward, and the medullary laid under it; so in Fowls, the lower frame of the brain, which consists of a thick and closer substance, is instead of the Cortex or shell; but the outmost and upper Membrane, chambering the Ventricle, appears medullar or marrowy above any other part. Moreover, the Ventricles in the brains of a man and four-footed beasts are placed beneath, and near the bottom; in Fowls, above and nigh the outward border. The reason of this difference seems to be, because in a more perfect brain, such as is in man and four-footed beasts, the animal Spirits have both their birth and exercise; viz. they are procreated in its Cortical or shelly part, and in its medullary, which being large enough, lyes under this, they are circulated and variously expanded for the acting of their faculties. But truly in the brain of Fowls there is space enough for the generation of Spirits, but for their circulation there is scarce any left: to wit, the brains of Birds seem not to be much possessed with the gifts of phantasie or memory: yea it is thought, that the Spirits begotten in the brain are exercised chiefly in the oblong marrow for the pre∣serving the animal function; for there, as we shall shew anon, the medullary sub∣stance, which is instead of the callous body, consists; and like the streaked bodies in others, in these are streaked Membranes, through which the Spirits, procreated in the brain, are carried, without any order there, forthwith into the oblong mar∣row: but because the Spirits, begot in the brain, ought to lay aside a serous excre∣ment; therefore the Ventricles, from the complicature of the streaked Membrane upon the keel or lower part of the brain, and on the shanks of the oblong marrow it self, do serve conveniently enough for this business. Notwithstanding, because in the brains of Fowls, the Fornix is wholly wanting, there are only two anterior Ven∣tricles; between which, the Choroeides infolding is stretched out; the veinous portion whereof, as was but now said, arises a little lower from the fourth bosom; but the Arteries ascending, come from either side of the oblong marrow.

Nor is there a greater heterogeneity or difference of conformation in the Brain it self of Fowls, than in the oblong marrow from the same in men and four-footed beasts. For in the first Section, from whence the Optick Nerves arise, two noted protuberances grow to either side. These are much greater in proportion than the orbicular prominences in the more perfect Creatures; so that they seem another additional brain: either of them of a white colour, and purely marrowy, is hollow within; so that in these kind of Animals are found two bellies or Ventricles in the brain, and as many in the oblong marrow. And seeing in these, as in all other Ani∣mals, a cavity is put under the Cerebel, the Ventricles in the whole Head differ as well in number as in figure and position.

In the middle of the medullary Trunk, to wit, where those prominences grow to its sides, the Chink, leading to the Tunnel, is cut, but into it the aperture of either Ventricle gapes or opens, that it is not to be doubted, but that the serosities heaped up there, are sent out by that way. Moreover it is likely, that these hollow and me∣dullary prominences in Fowls supply the course of the callous body, to wit, in which the animal Spirits are circulated for the exercising their faculties: because in the brain the space is so narrow, that the Spirits cannot be produced and circulated together within its confines. Further, as in Fowls, the use of the animal Spirits is required for the act of the sensitive and loco-motive faculty, more than for phantasie or me∣mory; certainly the chief place where they may meet and be exercised, ought to be placed rather in the oblong marrow than in the brain.

The Carotidick Arteries, which carry the blood to the brains of the greater Birds, are so small, that there is no proportion of these to the same in man and four-footed beasts. Their Trunks being carried within the Skull, ascend without any branchings into net-like infoldings, after the same manner as in other Animals, nigh to the pi∣tuitary Glandula, and pass right into the brain, and distribute some small shoots of the Vessels both to its exterior compass, and through its inward recesses. But in truth, the brains of Birds are watered with a very small portion of blood, in respect of other living Creatures; because, where the fancy or imagination is little exerci∣sed, there is not much blood required for the refreshing the animal Spirits.

Fowl (otherwise than some affirm) have both the mammillary processes, and the Cribrous or Sieve-like bone. For the anterior productions of the brain being highly extenuated and involved with the dura Mater, stretching out almost to the middle part of the bill, are inserted into the triangular bone, which hath a double bosom, distinguished between with a thin mound or pale. But these processes being dilated within the bosom of the aforesaid bone, and in Bladders full of clear water, which are very like the mammillary processes in a Calf, full of clear water. Besides, as out of the fifth pair of Nerves, a noted branch on either side passing through the ball of the Eye, enters into the cavern of the Nostril, a shoot of it being sent out of the Trunk, is bestowed to the very orifice of the Nostrils; in the mean time, both the greater Trunks, compassing about the Cribrous bone, meet together, and presently going one from the other, and being carried to the end of the bill, are distributed into the palate. After this manner Fowls, even as men and four-footed beasts, are furnished with a peculiar organ of smelling, to wit, with a double mammillary pro∣cess; and besides, they have within the Nostrils additional Nerves out of the fifth pair, by whose action and communication of branches into other parts, and among themselves, so strict an affinity is contracted between the smell and the taste. The other pairs of Nerves are almost after the same manner as in men and four-footed beasts. In like manner we also observe, that there is no great difference as to the Cerebel and the other portion of the oblong marrow, between Birds and the other Animals we have already considered on, unless that the orbicular prominences before the Cerebel, and the other annulary under it, meeting within them, are both wanting in Fowls; indeed these latter seem not at all to be required; but instead of the for∣mer, they are easily supplied from the hollow medullary prominences, such as we have shewn to be in Fowls.

And these are what are chiefly worth noting to be found in the brains of Fowls. We have already mentioned, that there is a certain likeness between these and Fishes as to the most parts of the head: wherefore it will seem to be to the purpose, that here for a conclusion we should say something of the brain of Fishes. First, we shall observe, that as the heads of Fishes, in respect of the whole body, are greater than of any other living Creatures, yet they contain in them less brain than others. For

two little moles or substances, placed before, sustain the whole place of the brain, properly so called; out of these, two signal smelling Nerves proceed, which are car∣ried by a long and straight journey to the holes made hollow, out of either side of the mouth, and which are instead of nostrils: and this is singular to Fishes. Moreover, we advertise concerning the Optick Nerves, that they, as in other living Creatures, inclining mutually one to the other, are not however united, unless perhaps towards the superficies; but they are crossed, and a Nerve arising from the right side of the oblong marrow, is carried into the left Eye, and so on the contrary: so indeed, that the visory rays have their refraction, not only in the Eye, but within the very bodies of the Nerves. The oblong marrow in Fishes, wholly after the like manner as in Birds, hath two signal protuberances hollowed within; and in truth, as to local motions, the Spirits in either seem to the exercised after the like mode. For as Fishes swim in the water, so the flying of Fowls or Birds seems a certain kind of swim∣ming in the Air. Further, in these 'tis observable, there are the pituitary Kernel, the Tunnel, and the Carotidick Arteries as in other Animals; also many pairs of the Nerves have the same origines and distributions, excepting that the hearing Nerves are here wanting; although Casserus Placentinus attributes this gift to the smelling Nerves. The figure of the Cerebel is the same as in more perfect Animals. Besides, what we have remarked concerning the wandring pair of Nerves in man and four-foot∣ed beasts; to wit, many fibres of it arising together, the trunk of the Nerve from the spinal marrow comes to them: in like manner the same is in Fishes. But to describe them all further is needless: for the rest, as those which are proper to them only and Birds, as also those which they have common with Fowls and the more perfect Animals, may be easily known, partly out of the peculiar similitude with birds, and partly out of the universal Analogy of all. Therefore we will now philosophise upon the Use and Action of the Brain and its Parts, and of its Appendix, together with the whole oeconomy of the animal Function: where in the first place, we will inquire into the offices of a more perfect Brain, such as of man and four-footed beasts; and also secondarily and collaterally we shall explain the Offices and Actions of a less per∣fect Brain, and of its Parts, such as that of Fowls and Fishes.