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. XVI. Of the various Order and diverse manner of Exercise of the Spirits produ∣ced in the Cerebel for the Acts of the involuntary Function.

AFter having shewn, that the office of the Cerebel is to procreate animal Spirits apart from the Spirits begotten in the Brain, and to dispense them into the Nerves, the Executors of the involuntary Actions and Passions; there yet remains to be unfolded by what manner of oeconomy or government the Spirits inha∣biting the Cerebel and made free, are busied both by an intestine Circulation, within their proper dwelling places, and also are wont to be expanded and flow out with an exterior irradiation for the necessities and wants of other parts: then these things being shewn, we shall design more particularly the Uses and Offices of the Nerves, and of some other Processes doing service to this Government.

As to the first, as the Cerebel is the other primary Root of the sensitive Soul, or the Fountain from whence the animal Spirits, being diffused through the whole sub∣stance of it and its Appendix, are continued still under the same Systasis and radiant Contexture, it is to be noted, that this radiation of the Spirits from the Cerebel doth flow after another manner than the other from the Brain: because this being left to it self, is bestowed by a constant efflux or flowing out on the Organs both of the vital Function and the merely natural, and its expences by an equal continual provision of Spirits, are made up again from the bloody mass continually instilled in. But on the contrary, the Spirits flow out from the Brain, neither by such a continual course without intermission and by little and little, nor are sustained by a perpetual provision and sliding in by degrees; but both the loss of them, and their refection, are uncertain, unequal, and variously interrupted. For neither are the spontaneous Acts of the Function it self, to which they serve, performed after any constant or always the same manner; but according to exterior accidents and occasions we put them forth by heaps, and with a certain force sometimes, and again sometimes we suffer them to be wholly intermitted and unimployed. Therefore the Spirits also are in like manner supplied with an uncertain measure; to wit, they are instilled in sleep plentifully and more copiously, but waking more sparingly and with hard labour, or scarce not at all. Yea the involuntary portion it self of the sensitive Soul (which flows from the Cerebel) for that it hath a near commerce and affinity (as was already said) with the other radicated in the Brain, therefore it is wont to be much disturbed in the performing its office equally and peaceably, and being variously affected and agitated by the impulses sent here and there, or from this place and that, it is com∣pelled, sometimes to contract, sometimes to extend its Systasis in the whole or in part, and so is rendred obnoxious to several Passions, and ordinarily instigated to the performing irregular and disorderly actions.

But indeed the contexture of the Spirits, or the part of the Soul irradiating the Cerebel and its Appendix, is both affected with a certain sense, and is urged into motions appropriate to it self, though divers. The sense or Sympathy belonging to this, if it be terminated within the confines of the Cerebel, is always private, nor goes any farther forward to the Brain with a more strong undulation or wavering; and because it is performed the living Creature knowing nothing of it, unless by the effect it cannot be known, for that it excites a peculiar motion. But such an affe∣ction of the Cerebel is implanted in it, that by every new disposition of the Praecordia and Viscera communicated to this from beneath, also from every violent passion ex∣cited within the Forum of the Brain, and so sent from above, a certain impression is carried to the inhabitants of the Cerebel: by which indeed they are disposed into va∣rious ordinations for the performing these or those motions respectively.

For examples sake, so long as the tranquil region of the Cerebel, like a serene and fair Heaven, is free from all perturbation, the Spirits its inhabitants, being poured out with a pleasing sense, or as it were a certain complacency, flow within their pro∣per habitations, both with a gentle circulation, and also with an equal flowing out enter the beginnings of the Nerves serving to the Functions both vital and natural: by which indeed easie Respiration, the Pulse, Chylification, and other offices of the

same nature, are performed peaceably. But if that any trouble or molestation hap∣pen outwardly to any one, from whence an impression of it is communicated to the Cerebel, presently a troublesom sense being stirred up there, it disturbs the animal Spirits in the Fountain it self, and so is wont to excite irregular motions in the Organs of the involuntary Function. For from hence the frequent alteration of the Pulse and of Respiration, also Cramps of the Viscera, and convulsive motions arise un∣known to us, or also against our wills. But an impression sent from elsewhere to the Cerebel, and inducing the same kind of troublesom sense, either ascends by the pas∣sage of the Nerves from the Praecordia and Viscera, or it is carried from above from the Brain by the passage of the orbicular Prominences; as shall be shewn more largely anon.

In the mean time, from these things already shewed of the passive power or sense of the Cerebel, it may be easily collected, by what means, with what order and se∣ries the animal Spirits, arising from the same, are moved. But first you must distin∣guish between their twofold motion. For one is customary and ordinary, consisting in a perpetual and equal efflux of Spirits; by which indeed, they flowing into the beginnings of the Nerves nigh their risings, especially of the intercostal and wandring pair, the solemn acts of the Pulse, Respiration, Chylification, and others of the involuntary Function are performed. Then secondly, the other motion happens extraordinary and occasional, which the same Spirits perform confusedly, as it were in disturbed orders: as when the Pulse becomes quicker or slower than it ought, or the Respiration unequal or interrupted; and when the other Faculties, which belong to this Class, are perverted from their regular and constant manner. But these kind of extraordinary motions are again twofold, to wit, for that its instigation proceeds from a double bound; for the impulse whereby the Spirits inhabiting the Cerebel, are compelled into an irregular action, (as we have but now intimated) is carried either from beneath, viz. from the Praecordia and Viscera; or it is wont to be trans∣mitted from above, to wit, from the Brain.

As to the first, if at any time the Praecordia grow too hot, and are burnt with a fea∣verish heat, presently by the passage of the Intercostals and the wandring pair of Nerves, the Spirits residing in the Cerebel, being warned of this evil, institute more frequent and stronger acts both of the Pulse and of Respiration. In like manner, if by chance the humors and sharp Juyces irritate or greatly trouble or afflict the Coats of the Ven∣tricles or Intestines through the sense of this affection communicated to the Cerebel, the instinct of performing the motion is reciprocated, whereby the fibres of the parts, being contracted and wrinkled together, endeavour the shaking off of the hurtful matter. More instances might be here brought of all the other acts of the vital or merely natural Function: of which besides it may be observed, that when a sense of the trouble is immediately conveyed from the Praecordia or Viscera to the Cerebel, this affection, like the waving of waters, is either stopt or terminated there, from whence a motion, as the business requires, unknown to the Brain, is presently retorted, as when the actions of the Praecordia are altered by a feaverish distemper without our knowledge; or secondly, that sense of the trouble being transmitted to the Cerebel, for that it is more vehement, it unfolds it self more largely, and like a stronger wa∣ving of waters, passing through the Cerebel, goes forward further even to the Brain, and warns its inhabitants of the evil; by which they being incited to oppose the ene∣my, cause a motion of another kind: So (as hath been said) when the Praecordia grow cruelly hot, the Cerebel feeling this, makes the Pulse and Respiration stronger. But further, the Brain being warned of the same trouble, seeks and diligently re∣quires cold drink and other remedies to moderate the heat. Moreover, it is after this manner also in several other actions, which though they are regular, yet being made in the Brain without any previous knowledge, they are said to be done by In∣stincts merely natural; as when brute Animals, being newly brought forth, pre∣sently seek for the Dams teats, and greedily suck; or Birds, without any shewing or example, build nests with wonderful Art, lay eggs, and hatch young ones. In these kind of works the Brain being taught before by none, directs fit means to the ends instituted by Nature: which indeed seems to be done by this means. The sense of every necessity being brought to the Cerebel, incites the Spirits inhabiting it to succour it; which when they are not able to do, the impression going from thence further forward, is carried to the orbicular Prominences: by which the Spirits there inhabiting, being presently struck, form the Appetite or the intention of performing,

which being thence communicated to the Brain, it readily causes that local motions, fit for the executing of the work, be retorted. Of these we shall speak anon a little more largely, when we treat of the respect which happens between the orbicular Pro∣minences and the annular Protuberance.

In the mean time, we shall take notice in the second place, that the irregular mo∣tions of the Spirits inhabiting the Cerebel, are wont also, by reason of the force of the affections, to be transmitted from thence to the Brain: for as often as a violent passion, as Joy, Sadness, Anger, Fear, or of any other kind, is conceived in the Brain, presently the impression of the same being brought through the by-paths of the Prominences into the Cerebel, disturbs the Spirits destinated to the vital or mere∣ly natural Function in their very fountain, and for that reason presently induces no∣table mutations in the Organs of those Functions.

What hath been spoken hitherto of the Cerebel being imployed about the offices of the involuntary Function only, also concerning the sense and the motions both usual and irregular of the Spirits inhabiting it, will be made more clear, if lastly we shall shew the offices of the Nerves and of the other processes, immediately depend∣ing upon the Cerebel, to be no other than such as perform only involuntary Acts: which shall be briefly and succinctly done, as far as is pertinent to our purpose, because a more full consideration of them is left to another place.