Dr. Willis's practice of physick being the whole works of that renowned and famous physician wherein most of the diseases belonging to the body of man are treated of, with excellent methods and receipts for the cure of the same : fitted to the meanest capacity by an index for the explaining of all the hard and unusual words and terms of art derived from the Greek, Latine, or other languages for the benefit of the English reader : with forty copper plates.

CHAP. XXIX. Of the Reason of the difference that happens between the Nerves of the wandring and Intercostal Pair in Man and brute Beasts; also of the other Pairs of the Nerves arising both within the Skull, and from the Spinal Marrow: also something of the Blood-carrying Vessels which belong to the Spinal Marrow.

THus far we have described all the Nerves stretching out to the Praecordia and Viscera, also to most of the other parts, which are the Organs of the involuntary Function, according to the manner by which they are wrought in man; and we have shewn their Offices and uses, and the Reasons of the most noted appearances in all. Before we proceed to the other Conjuga∣tions of the Nerves, it behoves us to shew with what difference the aforesaid Nerves are found in brute Beasts, and for what end such a difference is ordained.

It was already intimated, That the Trunk of the wandring pair in four-footed Beasts doth send forth to the Heart and its Appendix more nervous Vessels than in Man. The reason of which is obvious; be∣cause the Cardiack nerves in Brutes proceed almost only from this pair, and scarce at all from the inter∣costal, wherefore when they are only of one orgination, therefore more are required, all which not∣withstanding are much fewer than the same are in Man from a double stock, viz. being carried from both the Nerves: forasmuch as Beasts want prudence, and are not much obnoxious to various and divers Passions, therefore there was no need that the Spirits should be derived from the Head into the Praecordia by a double passage, viz. that one should be required for the exercise of the vital Function, and the other for the reciprocating impressions of the Affections; but that it may suffice, that all those destinated to every one of their offices, may be carried still in the same path.

In most Brutes the intercostal Nerve goes alone from the Ganglioform infolding of it almost without any branching to its infolding of the Thorax: in which passage however it is not always after the same manner in all; for in some it is carried single and apart from the Trunk of the wandring pair, nor doth it communicate with it in its whole journey, unless a little higher by a shoot sent down from the Ganglio∣form infolding: but in many the intercostal Nerve passes presently from its Ganglioform infolding into the neighbouring infolding of the wandring pair, Fig. 10. C. where, when both nerves seem to close to∣gether, from thence both being involved under the same common inclosure, as it were one Trunk, they are carried together till it comes over against the first Rib, and there an infolding being made, the intercostal nerve, departing from the wandring pair, is carried into the infolding of the Thorax; and the other nerve also is stretched between this and that infolding: which nerves, when one is carried under the other above the Artery of the Chanel-bone, making as it were an handle, straiten its Trunk, Fig 10. g.

Although the intercostal Nerve is carried from the Throat to the top of the Thorax under the same sheath with the Trunk of the wandring pair, yet it is not united to it; but they remain distinct still both of them in the whole tract, and the Membrane being diffected, they easily separate one from the other, unless they be knit together by some fibrils sent from one another in some places: but forasmuch as by this means the intercostal nerve being joyned to the Trunk of the wandring pair, goes under its cover, it seems to be so made only for its safety and better passage: wherefore in some perhaps where the intercostal Trunk is greater, or the course of its passage shorter, where such a safeguard is not needful, it descends alone. We have seen this Nerve covered with the safeguard of the wandring pair of one side, and in the other to have gone out by it self alone.

Whether the intercostal Nerve departs from the lower Infolding of the wandring pair or not, however a branch is stretched out between this infolding and that of the Thorax in many, perhaps in all brute Beasts, which in its passage binds about the Vertebral Artery, whereby the Sympraxis or joynt Action between the Praecordia and the exterior Organs of Respiration is sustained: yea from this lower infolding of the wandring pair sometimes we have observed a shoot and fibres to be carried to the beginning of the Bra∣chial branch, in which the nerve of the Diaphragma is rooted; also sometimes, though rarely, we may have seen some shoots sent from the infolding of the Thorax towards the Heart and its Appendix. In a Monkey above this infolding of the Thorax, as we have intimated before, were some shoots and small branches reaching from the intercostal nerve towards the Praecordia.

We may take notice concerning those Nerves below the Praecordia, distributed every where into the Ventricle and the lower Viscera, that there is scarce any difference of them in Man and Beasts. The nerve of the Diaphragma is placed lower in four-footed beasts: the reason of which is, because the Brachial nerves, out of which that ought to proceed, arise lówer; to wit, because Brutes have longer necks, as if destinated to the yoke. These things being thus premised concerning the difference of the Nerves in ei∣ther Species, it remains that we pass on to the unfolding the remaining pairs of them.

Therefore of those arising within the Skull, the ninth pair is made up of many Fibres also in its begin∣ning, (as was shewed before) out of which being gathered together, one Trunk being made is carried to∣wards the Tongue, through whose whole substance, to wit, from the bottom to the top, having passed, it disperses in its whole passage small shoots on either side, Fig. 9. 〈☐〉〈☐〉. So that nothing is more obvious than that this nerve performs the motions of the Tongue requisite for the articulation of Sounds, as the nerves of the fifth pair spread into this member, serve for the distinguishing of Tastes; for the exercise of either Faculty, viz. both motive and sensitive, the texture of Tongue being notedly fibrous, hath the virtue of a double Organ; therefore by the two nerves, besides the supplements of Spirits, are carried both the In∣stincts of the Motion and the sensible Impressions.

That the aforesaid Nerves of the ninth pair may more easily perform the motions of the Tongue, it sends forth downward one shoot before the entrance of the Tongue, which is united with a shoot from the tenth pair meeting it destinated to the Sternotbyroeidal Muscle; and the other little branch of the ninth Conjugation is distributed into the Muscles of the Bone Hyoides, Fig. 9. θ. θ. In truth these shoots being sent down as so many little ropes, conduce to the moving of the Muscles, which are fixed to the bottom of the Tongue, which Muscles being placed as so many Props to the Tongue, do facilitate its motion.

The Nerve of the tenth pair, although it may seem to arise within the Skull with many little Fibres also, yet being sent down from thence into the bony Cloisters of the Spine, not arising but within the first and second Vertebrae, it is carried without. Presently after its entrance it sends forth two nerves into the infolding of the intercostal nerve; for what end hath been already shewn: But its chief Trunk spreading downwards, and receiving a shoot produced from the ninth pair, is bestowed on the Sternothyroeidal Muscle. Moreover, this nerve reflects branches outwards, which are distributed into the Muscles of the Neck reaching out towards the hinder part of the Head; so this pair, as if it were only of the number or rank of the Vertebral nerves, imparts some branches to the intercostal nerve, and all the other shoots and branches of it serve for the performing of the motions of the Muscles of the Neck, Fig. 9. H. *. □. Δ.

So much for the Nerves arising within the Skull, which (as was shewn) having their being from the parts of the Brain or Cerebel, are destinated to the offices of the spontaneous or the involuntary Functi∣on, and are chiefly distributed into the Organs of the Senses or the Viscera of the vital and natural Facul∣ty. There remain many other Conjugations of Nerves, the roots or beginnings of which consist in the spinal Marrow, which is only the exterior production of the oblong Marrow. These spinal Nerves, be∣sides some branches that they bestow on the intercostal pair, are imployed almost wholly on the muscu∣lous stock, and the office of them is to carry outwardly the forces of the Spirits and the Instincts of the Motions to be performed, and to convey inwardly the impressions of sensible things. Forasmuch as the spinal Marrow seems to be derived from the Brain, and is as it were a broad and high road produced or leading from the same, without any paths or tracts inserted to it from the Cerebel, therefore the animal Spirits flowing within its nerves, do almost wholly execute the Acts of the spontaneous Functi∣on.

To describe all the several pairs of the spinal Nerves, and to rehearse all their branchings, and to un∣fold the uses and actions of them, would be a work of animmense labour and trouble: and as this Neu∣rologie cannot be learned nor understood without an axact knowledge of the Muscles, we may justly here forbear entring upon its particular institution: but it may suffice concerning these nerves and their medul∣lar beginning, that we advertise only in general what things may occur most notable and chiefly worth taking notice of.

As to the Nerves therefore produced out of the spinal Marrow, it may be observed, That in both sides of it, nigh the outward margine or brim, four or five Fibres arise in the superior brim, and as many in the infe•…•…ior: either maniple or handful pass through with distinct Fibres the Pia Mater, or the lowest Coat spinal Marrow, which is as it were the common sheath of them all; but afterwards the Fi∣bres passing through the third Membrane of either margine, (for three cloath the spinal Marrow) they joyn together, and having cloathed themselves with a Coat gotten from the second Membrane, they be∣come as it were one Trunk; which Trunk going out at the space between the knot of the Vertebre, is again divided into many nerves destinated to several parts. After this manner in the whole tract of the spinal Marrow, the Vertebral nerves have their birth; but in those places where the Brachial and the Crural nerves go out, both the thickness and the breadth of the spinal Marrow are increased, and also the handfuls or 〈◊〉〈◊〉 of the Fibres are larger. All these are well represented in Fig. 12.

The Brachial Nerves are not only far greater than the Vertebrals, so that they appear as it were large and broad nervous chords; but that they may conspire together, and serve for the strong motions of the Arms, or the fore-Legs of Beasts, it is observed, That very many of them are knit together by the cross nervous Processes. These Processes in four-footed Beasts (the fore-Legs of whom are destinated for un∣weariable

pains and difficult labour) are produced cross-ways after a curious manner, as may be discerned, Fig. 10. l. l. The use of these seems to sustain not only the consent of action in many nerves together, but also their mutual strength; that some bands of Spirits might awaken or stir up others, and for the exer∣cising strongly the Iocomotive force, they might mutually support and relleve one another. And not much unlike this, the business is about the Crural Nerves, where nervous cords signally large, being produced from the Junctures of the Vertebrae, whilst they descend towards the Thigh, they which are above receive in their whole tract the nervous Processes which are sent out still from those below, Fig. 11. p. p. p.

We may yet take notice farther concerning the spinal Marrow, that as it sends out Nerves by bands, and as it were by troops, in an orderly series and military order; so its sanguiferous Vessels are disposed with no less signal artifice. For those which are carried in the superficies of the spinal Marrow, and the Arte∣ries, Veins, and other Sanguiducts, which are nigh its compass, do contain some things more rare and highly worth the noting.

In the first place we may observe, That the blood-carrying Vessels do cloath the whole substance or frame of the spinal Marrow, as well as the oblong Marrow with a thick series of shoots; which may be made more manifest to any one, if first of all Ink were injected into the Vertebral Artery; for from such an injection often repeated, it will easily appear, that the infoldings of the Vessels do cover as it were in the shape of a Net, the upper tract of the Marrow. But by what means these Vessels proceed on both sides from the Trunk of the Vertebral Artery, and also the blood-carrying Veins, which are destinated to the whole spinal Marrow, and the inferior portion of its arterious passages, doth not so plainly appear; because the bony Cloisters of the Vertebrae are not broken through without much labour, especially in grown up living Creatures; and in that work the beginnings and branchings out of very many Vessels are wont to be blotted out: But that we might more accurately search into these hid things, we made the dissections of several Embryons, in which we were able to dissect more narrowly into all the recesses of the Bones: fur∣ther, that all the tracts and branchings out of them might be the better perceived in all the Vessels, we did cast in divers coloured Liquors. And we had our desired wish: for presently we found with much ad∣miration, that those kind of Vessels, viz. Arteries, Bosoms, and Veins, which respect the Head, belong also to the spinal Marrow with no less a noted disposition of provision.

When we did dissect the Heads apart from the Spine, we did think, according to the Opinion of the Vulgar, that the Vertebral Arteries did belong only to the Head: and when there did appear in the cut off Trunk of the oblong Marrow three arterious branches (as they are described above in the first and second Table) therefore in the Explication of either Figure we have affirmed the Vertebral Artery to be carried with a triple branch into the hinder part of the Head. But the Vertebral Artery pays to the superior part of the Spine as great Tributes of Blood as to the Head it self; and that middle arterious branch, which is marked in the first Figure with the Letter T, in the second with S, doth not ascend into the Head, but descends from that concourse of Vertebral Arteries towards the Spine, and conveys downwards from the common flowing together of the blood there made by many Arteries, the Latex for the watring top of the spinal Marrow. Wherefore in this place it seems convenient, that we do not only correct that er∣rour of ours, but that we deliver an exact description of all Vessels which are destinated to the Spine, viz. which contain many wonderful things. As therefore these Vessels are of a threefold kind, viz. Arteries, Bosoms, and Veins, we will expose each of them particularly; and first concerning the Arteries we say.

The Arteries which carry the Blood towards the Spine, are disposed after one manner above the Heart, and after another below it. As to the first, whereas the Trunk of the Aorta being there cleft presently into many branches, departs from the Region of the Spine, therefore the Vertebral Artery is produced on both sides from its axillary branches, which ascending straight into the hinder part of the Head, sends forth a branch into the meeting together of every Vertebrae: But below the Heart, forasmuch as the Aorta, in its whole descent, lyeth on the Spine, two Arteries are received into the Spine from its bottom nigh its Internodia or spaces between the knots of the Vertebrae; so that if the Trunk of the Aorta be cut open long-ways, there will appear a series of double holes through its whole tract, after a most curious man∣ner, as in the head of a Lamprey.

The arterious Branches which are carried both above and below the Heart towards the Spine, becom∣ing presently forked, bestow one shoot on the neighbouring Muscles, and another they insert into the Junctures of the Vertebrae; which being carried within the bony den, is cleft presently into three branches, two of which are bestowed on the medullar Trunk, and the other on the Membrane compassing about the bony den before, Tab. 13. Fig. 3. a. b. c. d. e.

As to the shoots destinated to the medullar Trunk, they presently tending two ways, and meeting with either maniple or band of nervous Fibres, ascend towards their beginnings; and so one little Arte∣ry having got to the superficies of the hinder Marrow, distributes into it hairy Vessels: but the other ar∣terious shoot, which is the greater and chiefest, as soon as it attains the margin of the former Marrow, is carried from thence by an oblique passage into the middle fissure or clest of it, where •…•…eeting with a •…•…hoot of the pair of the other side, it is united to the same, and from that joyning together the arterious Trunk, as it were a common passage, and made up of either Vertebral shoot, descends into that cleft by the open space of one of the Vertebrae, and in that short passage both dispenses little Arteries on either

side, and also inserts them leaning on the Pia Mater more deeply betwixt the sides of the Marrow: and so whereas in the whole tract of the Marrow, the chief Trunk of every Artery is carried into the middle cleft, it seems at first sight, as if the same arterious Trunk were carried under the whole substance of the Marrow from the head to the tail, Tab. 13 Fig. 1. Further, as by a concourse of several shoots of either side, the spinal Artery descends above the cleft of the Marrow; so where the Trunks of the Ver∣tebral Arteries joyn together (which happens to be done sometime in the hinder part of the Head above the oblong Marrow, and often in the Neck above the spinal) an arterious branch somewhat bigger than the rest is stretched out downwards. This formerly (as we mentioned but now) we mistook for the third ascending branch of the Vertebral Artery. But I have often taken notice, that in Brutes, where the Vertebral Arteries have met together with an acute Angle above the medullar Trunk, they are presently, departing one from another, stretched out directly to either brim of the Marrow, from whence imme∣diately being bent back, they are carried again into a mutual meeting, so that between their two joyn∣ings together is made the figure Rhomboides, as it is in Tab. 13. Fig. 1. C. The reason of which without doubt is this; to wit, that the more rapid course of the blood going towards the Head might be hin∣dred by its flood being a little space divided.

The third Brancy of either Vertebral Artery being carried into the anterior Cavity of the bony Den, and being presently made forked, tends to the right and left, and is on both sides inoculated to the next shoot of the same side and by the cross process, they of either side are united after the same manner; and so all the Arteries of this cense or rank receive one another mutually, as it were links of a chain, in the whole tract of the Spine, and are continued in the same bending passage. If Ink be cast into the Trunk of the Vertebral Artery and most of the hollownesses of the Aorta, all these Arteries dyed with the same, will appear a pleasant spectale, like Net-work, as may be seen Tab. 13. Fig. 3.

The top of this arterious Infolding being carried into the Skull, inserts two shoots sent forth straight into the wonderful Net, and imparts two others going out side-ways on both sides to the Dura Mater: the lower end of the same reaching to the Os Sacrum, ends in very small Vessels which serve for the Mem∣brane of the Bone.

If it should be asked, For what end these Arteries being concatenated with such frequent ingraffings are disposed within the Back-bone: This seems to be so ordained for three uses: viz. First, These Vessels (as al∣so the passages of the Bosoms) are divaricated after this manner with repeated compassing about, that a constant heat from the blood being so turned about, as it were into frequent Whirlpools, might be sup∣plied about the compass of the spinal Marrow, as it were by a Balneum Mariae; even such a manner of office as the Choroeidal infolding performs within the infolding of the Brain. Secondly, Care is taken by this means, lest the blood destinated for the spinal Marrow, might flow thither too plentifully, or might be defective in its due influx; for the blood being about to flow into the medullar stock plentifully, is di∣verted from the little branches c. d. into these Emissaries e. f. and in its defect the subsidiary provision be∣ing called out of the middle infolding through the chanel e. into the Vessels c. d. is derived into the same medullar Trunk. Thirdly, The use of this arterious infolding seems to be, that the blood may be distri∣buted from its passages into the Membranes, viz. which is carried every where from them through the Capillary Vessels; the reliques of which also are supped back by the little chanels sent out of the bosoms. Further, from this Store-house, if necessity urges, a certain provision is had for the wants of the Brain; wherefore from hence the small Vessels end in the wonderful Net.

So much for the Arteries distributed about the Spine or Back-bone; the Vessels of the second sort are the Bosoms which come between the Arteries and the Veins for the use of the spinal Marrow no less than of the Head it self, and are here ordained with a more curious implication. But the reason why bosoms are required to these more noble parts, and scarce to any in the whole Body besides, is this, to wit, that about these bodies all manner of extravasation, or any stagnation of the blood, might be hindered: but sometimes the Veins are not sufficiently emptied, that they may presently receive from the Arteries the deposited blood, and so may prohibit any flowing out of it; wherefore the bosoms, as more fit receivers, are destinated to that office, for that their receptacles are larger and soon emptied; and for that reason they may more conveniently derive the blood from either medullar substance, lest it should overflow it in the Head or Spine.

As to the Figure of the Vertebral Bosom, its passages being conform to the arterious infolding, are put under it in the whole tract of the Spine: for after a like manner, in either bosom, which is extended with∣in the cavity of the bony Den, from the hinder pair of the Head to the Os Sacrum, there is one receiving Vessel, by whose twofold chanels presently the blood is brought back from either superficies of the Mar∣row into the bosom, and another carrying back, by whose passage the same is exported into the Veins. Moreover, in many Animals (though not in all) the bosoms on either side seem to be knit together upon the knots between the Vertebrae by the cross processes, and so communicate between themselves: either bosom in its top is continuued into the lateral bosoms of the Head; further, from it on both sides a passage lyes open into the Jugular Vein and into the Vertebral, Tab. 13. Fig. 4.

What the use of the aforesaid Bosom is in general was but now intimated; to wit, that the blood de∣posited from the Arteries in the spinal Marrow, might be presently emptied from thence, and be retained within the more large Cavities of the Bosoms, till it may be transferred into the Veins being made more emptied: But the reason of the divers sorts of implications, and the frequent ingraffings which is found

about their little chanels, seems to be, that the blood, if by chance it being plentifully heaped up within some part of the bosom, should there stagnate, or be apt to regurgitate into the Marrow, it might be drawn out by those frequent Emissaries here or there into the middle or opposite side: after a like manner it is with the bosoms about the Spine, as when a Country-man digs his ground frequent cross Furrows for the draining away any superfluous moisture.

There remains another use of the Vertebral Bosoms, of which we made mention before, to wit, that the blood nigh the medullar Body, being brought through their variously intorted Meanders, (like the ar∣terious infoldings) might yield heat requisite for the swift passage of the animal Spirits, as it were a Baln•…•…um Mariae. That the bending tracts and complications of the Bosoms may be the better seen, a certain tincture may be cast into the Vertebral Veins; and presently that invading the passages of the bosoms and marking them, will exhibit the appearance of a long Ladder with many little labels hanging to it.

Yea at length by those little roundles we are led to the third kind of Spinal Vessels, which are the Veins, into which all the bosoms immediately convey their burden, whereby they being continually emp∣tied, may be still able to receive fresh blood: wherefore the venous branch is stretched out by the several joyntings of the Vertebrae into the bosom, which presently carries away the blood laid up in it, and to be reduced towards the Heart. The Veins designed to this office, after the example of the Arteries, are disposed after one manner above the Heart, and after another below it. As to the first, a branch going from the Trunk of the Vena Cava below the Chanel-bone, or the first little Rib of the Breast, accompanies the Vertebral Artery, and ascending by the holes of the Processes between the several Vertebrae, inserts a little branch to the Bosom, Tab. 13. Fig. 2. b. b. b. Then the top of this Vein being carried towards the hinder part of the Head, is continued into the Trunk of the Bosom, and opened by the other passage into the Jugular Vein. But further, as if these communications were not yet sufficient for the draining away the blood, transverse branches also are stretched out between both Veins, Tab. 13. Fig. 2. i. i. i. So manifold diverting places appear, by which it is enough and more than enough provided, lest the blood might flow back towards the medullar Trunk upon any occasion. Below the Heart, because the Trunk of the Vena Cava cannot, as the Aorta, immediately lean upon the Spine,: and carry shoots straight to the same, therefore it sends forth a Vein without a Companion, out of whose Trunk forked or twofold branches being sent forth, go forwards both to the Muscles of both sides and to the Spine it self. Below the Kid∣neys, seeing there is a space granted for the Vena Cana to be carried nigh the Spine, the Azygos Vein ends, and from the Trunk of the greater Vein, as from that of the Artery, the Vessels belonging to the Loyns immediately proceed.

These things being lately observed concerning the blood-carrying Vessels belonging to the Spine and the hinder part of the Head, and here inserted in the place of an Appendix, ought to be referred to the other Doctrine of this kind, delivered above in the eighth Chapter. In the mean time, that we may re∣turn to our purpose, to wit, what remains of Neurologie, there is not much more to be met with worthy note concerning the Nerves: For they, as to the greater and chief Ramifications, are almost constantly both in Man and brute Beasts, after the manner we have described them. Sometime it happens, although very rarely, concerning the divarications of the smallest Shoots and Fibres, that there is some variety: but as to the primary Vessels, and those drawn from them, the Configuration of every pair of Nerves is still the same or alike in all. It now remains, that the Theory of the Nerves, hitherto drawn in words, and so only objected to the Understanding, may also be shewn to the Sense, which will make it clearer. Where∣fore we have taken care, that the ingraven Delineations of the wandring and intercostal pair of Nerves, and also of others which are of chief note, and of the Spinal Marrow it self be plainly exhibited. The Fi∣gures of these, although taken from a dead Example, yet after many Dissections and a frequent compar∣ing them together according to their several parts, they are described as if from the life; the Lineaments of which with Characteristical Notes, that they may be the better and more distinctly perceived, and a large draught of every Figure, equal almost to the Scheme of Nerves in their animated Body, we have caused to be cut: further, because the Contents of either side and of the Cavity between, cannot be at once described in their proper situation; therefore here it is supposed, That the Spine, with the oblong Marrow, or the whole medullar Stock, cut in the midst is rolled out, and both sides of it, with the pairs of the Nerves arising in the whole Tract, is turned outward.