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. XIX. Of the Nervous System in general, where its parts (which are the Nerves and Fibres) being designed, a prospect of the whole Animal Goverment is exhibited.

WHen as hitherto having beheld the several Regions of the Brain it self, the Cerebel, and medul∣lar Appendix, and the provision and offices of them all, we have designed or drawn forth the uses and employments also of the parts and processes, and the sanguiferous Vessels belonging to every one of these; it is now time for me to stop and retire into the Port from this trouble∣som and intricate Sea of Disquisition: But indeed, because I find that I have not yet reached to the farthest shores and utmost parts, but that beyond this Sea, which we have sailed through, as yet the nervous System, and very many Creeks or Bosoms, Meanders, and highly intricate Recesses or private places in it remain to be viewed; therefore although we know it is difficult to proceed with full Sail, we have re∣solved to undertake the task of the Doctrine of the Nerves; and the rather, because without the perfect knowledge of the Nerves, the Doctrine of the Brain and its Appendix would be left wholly lame and imperfect; for neither what hath already been delivered concerning them can be sufficiently undestood or illustrated, nor (which I chiefly desire, and is the end of the former Disquisitions) without those things before known can the Pathology of the Brain and nervous stock be rightly instituted. And indeed there are many things which might easily deter any one from such an undertaking: to wit, the hardness of the work, and full of hazard; which promises at first-sight more difficulty and thorny labour, than pleasure or profit. Then some will object, that this Province is already so perfectly cultivated, and adorned by former Anatomists, that by a repetiton of the same, I may seem to have medled with a thing done to my hand. But I may readily answer to these, first, That the Anatomy of the Nerves yields more pleasant and profi∣table Speculations, than the Theory of any parts besides in the animated Body: for from hence the true and genuine Reasons are drawn of very many Actions and Passions that are wont to happen in our Body, which otherwise seem most difficult and unexplicable; and no less from this Fountain the hidden Causes of Diseases and their Symptoms, which commonly areas•…•…ribed to the Incantations of Witches, may be found out and clearly laid open. But as to our Observations about the Nerves, from our following Discourse it will plainly appear, that I have nor trod the paths or footsteps of others, nor repeateed what hath been before told.

Therefore, that according to our determination we may enter upon the explanation of the nervous System, we shall comprehend under this name all parts, upon which giftcd with the animal Spirit, Moti∣on and Sense necessarily and immediately depend, to wit, for the performing either one only, or both to∣gether in the whole Body. But these kind of parts, in respect of the Head and marrowy Appendix, are like a branching stock or imps growing out of the trunk of a Tree: for supposing that the cortical sub∣stances of the Brain and Cerebel are in the place of roots, and that the substances every where medullar are taken for the stock or pith; the nervous germination or budding forth expanded into divarications of Nerves and Fibres, will appear like so many little branches, twigs, and leaves. Or if the Head contain∣ing in it self the chief part and power of the sensitive Soul, be taken for the body of some Luminary, as of the Sun or a Star; the nervous System shall be that radiant or beamy concretion compassing it about. Because the animal Spirits flowing from the Brain and Cerebel, with the medullar Appendix of either, as it were from a double Luminary, irradiate the nervous System, and so constitute its several parts, the Organs of Motion or Sense, or of both together, as hath been said.

The parts of the nervous System, as a radiant or beamy texture, are either primary, viz. the bodies themselves of the Nerves, into which the animal Spirits immediately flow from the Head and its me∣dullar Appendix; or secondarily, which are Fibres planted or interwoven in the Membranes, mus∣culous Flesh, Tendons, and some of the Parenchyma, which also contain in themselves animal Spirits; but they receive them not but mediately and secondarily derived from the Head through the bodies of the Nerves.

We have already shewed that the animal Spirits are procreated only in the Brain and Cerebel, from which they continually springing forth, inspire and fill full the medullar Trunk: (like the Chest of a musical Organ, which receives the wind to be blown into all the Pipes) but those Spirits being carried from thence into the Nerves, as into so many Pipes hanging to the same, blow them up and actuate them with a full influence; then what flow over or a bound from the Nerves, enter the Fibres dispersed every where in the Membranes, Muscles, and other parts, and so impart to those bodies, in which the nervous Fibres are interwoven, a motive and sensitive or feeling force. And •…•…hese Spirits of every part are called Implanted, forasmuch as they flow not within the Nerves, as the former, with a perpetual flood; but being something more stable and constant, stay longer in the subject bodies; and only as occasion serves, viz. according to the impressions inwardly received from the Nerves, or impressed outwardly by the objects, are ordained into divers stretchings or carryings out for the effecting of motion or sense either of this or that manner or kind.

Indeed the animal Spirits flowing within the Nerves with a living Spring, like Rivers from a perpe∣tual Fountain, do not stagnate or stand still, but sliding forth with a continual course, are ever supplied and kept full with a new influence from the Fountain. In the mean time, the Spirits in the rest of the ner∣vous kind, especially those abounding in the Membranes and musculous stock, are like Ponds and Lakes of Waters lately diffused from the chanels of Rivers, whose waters standing still are not much moved of their own accord; but being agitated by things cast into them, or by the blasts of winds, conceive divers sorts of fluctuations.

But because there is no light difference between the motions and consistency of the Spirits and of Waters, perhaps it will better illustrate the matter, if the Spirits of either kind, to wit, the inflowing and im∣planted, are compared to the beaming forth of divers rays of light. And so when light is let into a dark chamber, and presently inlightens the whole, we may c•…•…nceive the particles of the light so swiftly diffused to be of a twofold kind; to wit, some are bodies sent from the light it self, which diffuse themselves every way into an Orb; and other luminous particles are as it were Etherial little bodies existing before in the pores of the Air, which being agitated by the former, and as it were inkindled, cause as it were a flamy, though most thin contexture, stretched out in the whole clearness. After the like manner, the animal Spirits flowing from the medullar substance into the Nerves, are as it were rays diffused from the light it self, and the other Spirits every where abounding in the Fibres, are as so many lucid particles included and implanted in the Air, which are actuated by the former, and being stirred up by them into motion, perform the acts both of the sensitive and locomotive Faculty.

That it may better appear by what means the animal Spirits do irradiate and swiftly pass through the parts of the nervous System, both primary and secondary; so that light is scarcely carried swifter through a diaphanous Medium, than the communication of the Spirits is made from one end of the nervous Sys∣tem to the other; it will be requisite to inquire here a little concerning the Origine of the Nerves and nervous Fibres, also of their Fabrick and Conformation, to wit, what pores and passages either of these bodies have, and how disposed for the passing through and commerce of the animal Spi∣rits.

As to the Nerves, it is manifest from what hath been said, that all of them are produced immediately out of the medullar Trunk or its processes; so that as these parts are the common and broad roads which lead both from the Brain and from the Cerebel, all the Nerves are particular paths reaching out from them on every side into the several Regions of the animated Body. Wherefore the same Marrow, which is the original of every Nerve or Sinew, foras•…•…uch as it is drawn into a more thin thread, consti∣tutes the matter of the same Nerve; which indeed, that it may be made more solid and compact, is cloathed with a peculiar production of the Pia Matcr, for as from a Silver mass gilt or inriched with

Gold, all the threads produced from it are gilded; so the same Membrane, which covers the medullar Trunk, is produced to gether with all the Nerves coming out from the same, and cloathes them all. Fur∣ther, very many Nerves arising together out of that marrowy beginning, go forth as it were by bands; which notwithstanding, for the sake of the better passage, being presently united and carried out of their bony Cloister, are included in a common Coat taken from the Dura Mater. For we suppose (which also shall be more clearly shewed anon) that all the Nerves, destinated to any parts or every particular mem∣ber, do arise distinctly and apart, and so remain in their whole passage. But in that oftentimes a Nerve appearing as it were one Trunk, afterwards seems to go into many branches, it is because those branches being indeed singular, and divided in the whole passage, are collected as it were into one bundle; for sometimes we have separated those Nerves, seeming to grow together as it were into one rope or cord of of a Nerve, one from another, dividing them to their very original; for neither otherwise could the In∣stincts of the Motions to be performed be carried so respectively to these or those parts, separate one from another, to which the branches of the same Trunk belong.

The passages of the Nerves are not bored through as the Veins and Arteries; for the substance of those are not only impervious to any Bodkin, but no cavity can be seen in them, no not by the help of Specta∣cles or a Microscope. As to what belongs to the smelling little Pipes, they seem to be so made, not for the passage of the animal Spirits, but that some serosities might slide down that way: but the Spirits them∣selves are carried in the sides, and not in the cavity of either Pipe; but the substance of the other Nerves appears plainly firm and compacted, that the subtil humor, which is the Vehicle of the Spirits, may pass through their frames or substances, even as the spirits of Wine, the extended strings of a Lute, only by creeping leisurely through. Hence it may be argued, that because the animal Spirits require no manifest cavity within the Nerves for their expansions; neither is there need of the like for them within the substance of the Brain; but that the Ventricles, commonly so called, ought to be deputed to some other office than this.

But the Nerves are white, smooth, and round bodies: within the Skull and nigh their beginnings, being as it were only covered with the Pia Mater, they are soft and easily broken; without this, for that many of them are for the most part gathered together, and also cloathed with the Dura Mater, they become somewhat hard and more tenacious. The Nerves themselves (as may be discovered by the help of a Microcosm or Perspective-glass) are furnished throughout with the pores and passages, as it were so ma∣ny little holes in a Honey-comb, thickly set, made hollow, and contiguous one by another; so the Tube∣like substance of them, like an Indian Cane, is every where porous and pervious. Within these little spaces the animal Spirits or very subtil little Bodies, and of their own nature ever in a readiness for motion, do gently flow; to which is joyned, both for a Vehicle, as also for a Bridle or stay, a watry Latex, and that it self of very subtil parts. This Humor diffuses, with its fluidity the Spirits through the whole nervous System; also by its viscosity retains them, that they be not wholly dissipated, but as it were in a certain Systasis and continued Series; for it seems, that without such an Humor the Spirits could not consist within the nervous stock, but they would vanish away into Air. Further, the same Humor is no less re∣quired for the passing through of the sensible Species: because the animal Spirits, we suppose, like the rays of Light, to be diffused through the whole nervous System; and those rays, unless the humid particles of the Air be mingled with them, do not easily transmit the forms or images of things; as is obvious in an Optick Scene, which is hid or shadowed by the clear beams or brightness of the Sun. And in like manner, from the defect or depravation of the nervous Juyce, we can readily shew, that the inordinations of the animal Spirits, and oftentimes most horrid distempers of the Brain and the nervous stock do arise.

This nervous Juyce being derived from the Brain and Cerebel into the medullar Appendix, is carried from thence by a gentle sliding down through the Nerves even into the whole nervous stock, and waters its whole System. Upon the equal emanation of this depends the expansion of the animal Spirits through the whole; and the substance of these, yea the Hypostasis of the sensitive Soul it self is founded on the diffu∣sion of the same humor. The animal Spirits being lest to themselves, follow the motion of this Juyce, and flowing together with it in the same course, are pleasingly or quietly expatiated; but in the mean time, as occasion is offered, the same Spirits, as a breath moving upon those waters, conceive other spreadings abroad, and those more rapid. For as in a River, from winds or any thing cast in, divers undulations or wavings are stirred up; so the animal Spirits being raised up by objects, for the performing the offices of sense and motion, do tend this way or that way to and fro within the nervous stock, and are agitated hither and thither by other means.

But to return to the parts of the nervous System, besides the Nerves themselves, Fibres also being dis∣persedly interwoven in the Membranes, the musculous Flesh, the Parenchyma, and other parts, and uni∣ted in the Tendons, are the Organs of sense and motion. Yea, the acts of their faculties are principally and more immediately executed by the Fibres than the Nerves; for they, by drawing together the Muf∣cle and other motive parts, cause the motion it self; but the Nerves only carry from the Head the in∣stinct for the performing of that motion. In like manner, in Sensation the Fibres receive first of all and immediately the impressions of sensible things, and express the same (as musical strings do the strikings of a quill or fingers) by an intrinsecal modification of the Particles, and represent the various approaches of the object by the like motion of the Fibrils, as by a moveable and fluid Character, whose Idea the Nerves transfer only to the Head.

Concerning the nervous Fibres it behoves us to inquire from whence they have their rise? For it ap∣pears plainly, that they arise not immediately from the Head or its medullar Appendix; not is it less im∣probable, that they are produced (as 'tis commonly said) from the Nerves: because what is asserted, that the Fibres are productions of the Nerves, and little bits or pieces of them torn off, as it were into hairy branches, seems unlikely; for that the Fibres in some parts, being placed nigh, exceed in their bulk the magnitude of the Nerve that is brought to that part, at least an hundred-fold: which thing appears clearly from the Tendon of every Muscle, which being made up of united Fibres, is observed to be far greater than the Nerve inserted to it. And indeed for almost the like reason we are induced to think the nervous Humor it self also, whereby the Membranes and musculous Fibres are wont to be watered, to be deri∣ved unto them not by the only means and passage of the Nerves; because it is heaped up much more plen∣tifully and in more abundance than can be carried thither through those narrow passages, as appears clear∣ly in Ulcers of the Kings-Evil, or in Impostumes or Wounds of the Tendons and nervous parts, in which a glutinous Humor drops forth in so great abundance, that all the Nerves of the whole Body could scarce be able to supply it.

Wherefore concerning these, it seems that we may affirm, that the Fibres are not continued portions of the Nerves broken off into little hairy strings or Capillaments; and that all the Fibres originally proceed not from the Nerves, because some of them, viz. those interwoven to the Heart and its Vessels are of e∣qual birth with the Nerves themselves, and coexist with them together from the beginning. However the most Fibres, as to their production, depend upon the Nerves; and all, which way soever brought forth, receive constantly from the Nerves the forces and supplements of the animal Spirits, and also Instincts of the Motions to be performed by them.

Therefore to recount the births or kinds of Fibres; they are first either spermatick and first begotten, the rudiments or first beginnings of which being of the like antiquity as the Heart and Brain, placed in the Conception, afterwards leisurely increase; to wit, such are, as hath been said, those in the Heart it self in its depending Vessels, the Membranes and some other parts, which form the first stuff or threads of the Embryo: or secondly, other Fibres are produced secondarily, and by a second birth; of which sort chiefly are such which are interwoven into the parts taken for the compleating of the animal Fabrick, and especially those termed Sanguineous, which we think to be begotten after this manner.

The Heart and Brain, with the Arteries and Nerves hanging to them, are primigenious parts, and high∣ly original; but these, for the second birth of others, and for the nutrition and increase of all the sensitive parts, distribute a twofold humor: viz. one spirituous and endued with very active Particles which per∣petually flow, though but in a very small quantity, through the passages of the Nerves from the Brain and Cerebel; and the other slow and softer, which being every where laid aside through the Arteries from the bloody mass, is rendred more plentifully. This latter being of it self dull and thicker by much, is actuated by the former, and being imbued by it, as by a certain Ferment, acquires strength and power of growth or vegetation. But indeed the nervous Juyce, forasmuch as it diffuses with it self the animal Spirits, imparts to every part, besides the faculties of Motion and Sense, the determinations also of form and figure. Further, whilst that, being joyned to the other arterious humor, is disposed into the sub∣stance and matter of the member or part to be nourished, it forms some tracts as it were, to wit, the Fi∣bres themselves, in which the animal Spirits, coming together with them, reside and are expatiated. These twofold or twin humors, coupling together in every sensitive part, constitute a liquor truly nutri∣tious, to wit, which is both spirituous and nourishable. And in truth, both these Juyces, viz. the nervous and arterious, being married together, are as it were the male and female seed, which being mingled in a fruitful womb, produces the plastick Humor, by those virtue the living creature is formed and increases. Hence may be observed, as the particles of the spirituous liquor, or of the other more watry juyce (viz. this latter being supplied from the Arteries, or that from the Nerves) are strong or excel, as to their pro∣perties or powers, all living creatures become more or less nimble, active, and ready to any motion and labour. Besides, from the default or depravation of the one and other humor excelling, the sorts or kinds of this or that disease are excited; concerning which, and also what belongs to the explication of the nu∣tritious Humor, we may perhaps have some other time occasion to discourse.

The animal Spirits which enter and fill the ordained series of the Fibres as so many little places, flow thither by the passages of the Nerves, notwithstanding the Spirits which are seated in the Fibres, inter∣woven with the musculous stock, receive nourishment, yea and as it were auxiliary forces, from the arteri∣ous blood there plentifully slowing: whereby indeed both the Spirits themselves acquire for the performing of Motions a greater force and as it were elastick; so that their force being stirred up by a strong endea∣vour, it seems like the explosion of Gun-powder; and also the same Spirits being continually consumed within the Muscles more profusely than is wont to be in the Membranes and other parts, are in some measure made up or repaired from the bloody sustenance: because whenas the arterious Juyce joyns more plentifully with the nervous flowing within the sanguineous parts, it may be well thought, that it also lays upon the Spirits brought thither with it, as it were some nitrosulphureous particles, and intimately fixes them on them; and so, by reason of this Copula, highly flatuous and apt to be rarified, the Spirits themselves become there more active, so that in every motive endeavour, whereby the Muscle is suddenly intumified, they, as if inkindled, are exploded. Moreover, a sudden refection of the consumed or wasted Spirits, after great exercise or labour, is for this reason also performed by the blood; for that the spirituou

particles being left and forsaken by motion, presently a new Copula of the same kind of matter, apt for explosion, is joyned to them. For it is not possible, that the immense loss of Spirits which happens in hard labours (if they were wholly destroyed) in so short of time, should be able to be restored by supple∣ments coming only through the Nerves. We shall discourse more largely of these things, if at any time hereafter we shall treat of the Motions of the Muscles.

The animal Spirits being disposed within the several Muscles, according to the series of Fibres, seem as it were so many distinct Troops or Companies of Souldiers; all which being set as it were in a Watch∣tower, are ordained, as a new impression is carried to them by the Nerves, either from the objects out∣wardly, or more inwardly from the Head, forth with into various forms and peculiar orders for the perform∣ing of motion or sense of this or that kind. The carriage or behaviour of these is worth the seeing in an animal newly killed and its skin taken off. For when life perishes, and all the force of the Spirits flowing in through the Nerves hath quite ceased: yet the Spirits implanted into the whole Body breaking forth from the Muscles, still move and shake them, and force them into several Convulsions and trembling motions.

From what hath been said we may gather, what the disposition or order of the animal Spirits may be in the whose animal Body: to wit, those procreated in the cortical substance both of the Brain and Cere∣bel, are congregated in to the middles of either, as it were into distinct Empories or Marts; and an ex∣pansion being made in either, they cause certain interior powers of the Sensitive Soul to be exercised; yet the same Spirits, affecting more room, enter the oblong Marrow (as it were the Chest, as hath been said, of a musical Organ) and fill it full; within which flowing, they carry to and fro the impressions of sen∣sible Things and the Instincts of Motions. From the oblong and spinal Marrow the same Spirits, unless when they are otherwise busied, tending outwardly, flow towards the several parts of the whole Body; which notwithstanding wandring so out of doors, because they pass through very strait ways in their pas∣sage, to wit, the slender bodies of the Nerves, they break not forth in heaps, or in a thick troop, but only contracted orderly, and as is were by bands or divisions: but they being carried beyond the extremities of the Nerves, and there possessing the Membranes, Muscles, and other sensible parts, dilate them∣selves as it were into a most ample field, and with a very diffuse Army they dwell in the Pores and passages of the Fibres planted every where about; where also being endowed from the blood with new food, they become more lively and more expeditious or ready for the designed offices.

Here perhaps it may be demanded, how the animal Spirits, diffused in such numerous troops through the habit of the Body, are able to be supplied by so strait chanels of the Nerves? To which we reply, That those which reside more outwardly do not quickly evaporate, nor are remanded back by Circulation: wherefore when all the Fibres are filled by an influx of the Spirits made by little from the beginning, very small supplements suffice to repair their expence: For neither are those dwelling more outwardly, for that they are repaired by the bloody food, much consumed, though in frequent action.

Hence may be noted the difference between the distributions of the blood and animal Spirits. That Latex, because it is reduced in a circle, its Vessels are in the whole passage proportionated as to the bulk of the Trunk and the branchings sent from it, to wit, so that the branches of the great Artery, being carried from the Heart, contain at the least so much of the blood, as the shoots reaching forth from them, into all the parts. But because the animal Spirits being once begotten and carried more outwardly, subfilt longer there, and evaporate very slowly and by little and little; therefore the Vessels carrying them, viz. the Nerves, in respect of the Fibres receiving rhem, are made much lesser in proportion; lest perhaps by too great a supplement of the animal Spirits, and the too thick gathering of the fresh ones still into the ner∣vous parts, the Army of the Veterans, before instructed, should be confounded, and so the orders of all be∣ing disturbed, the exercises of the animal Function should be performed any now. For indeed when at any time the Spirits are made too sharp, so that. being therefore struck as it were with madness, they rush upon the nervous System with tumult and impetuosity; from hence a great unquietness and continual throwing about of the Members are wont to be excited, to which sometimes madness and fury succeed.

In the order and ordination of the animal Spirits, such as was but now described, the Hypostasis or the Essence of the sensitive Souls consists to wit, which is only a certain Systasis or shadowy subsistence of those Spirits, which like Atoms or subtil Particles, being chained and abhering mutually one to another, are figured together in a certain Species. Moreover, the faculties of the same Soul depend upon the va∣rious Metathesis and gesticulation of those Spirits within the aforesaid Organs of the Head and nervous System. But the consideration of this Soul and its powers requires a peculiar Tract, which hereafter (God willing) we intend; in the mean time, our Method demands of us, that (accorging to our weak skill) by the cense or numbering of the Nerves, being particularly made, we should deliver an exact Neurology or Doctrine of the Nerves.

But for that in the premised general consideration of the Nerves and Fibres, there was mention made of the nervous and nutritious Juyce; notwithstanding what belongs to their powers and natures, hath been neither fully nor clearly enough delivered; therefore we will a little divert here, and make it our business to inquire what sort of Juyces and Humors are carried into the parts of the animated body for their nourishment, and by what ways or passages: then this difficulty being removed, a plain and easie way leads into the Doctrine of the Nerves.