to get it forwards Mr. Cowper Mentions an Experiment how by an Injection of Water into the Crural Arterie the Muscles of the Legs renue their Contractions From this he would infer that Muscular Motion is performed by the Blood as a Pondus but tho' his Myotomia Argues it came from an Inquisitive Author yet I rather an fully perswaded that the Blood does not Act as a Pondus because this Experiment pleads against it but to avoid a long dispute I shall only give the Reason of the Phaenomenon Before the injection of this Water the Branches of the Arteries are full of Blood and Arterial juice and when by the mixture of the Water with this juice it is attenuated and driven into the Glands faster than it can be received by the Venous Channels the most Subtile Part is by the force of injection strained into the Fibers and distends 'em so as to Contract the Muscle Perhaps here it will be objected that if the Water can thus pass through into the Fibers what need is there that the Nerves should lay down their contents in the Glandules I answer that the Water is thin and apter to pass through those Ducts than the Arterial juice which is thick and viscid wherefore it is necessary that the Nerves should lay down their contents there to Attenuate and Rarisie this Thick juice I have seen People inclining to a Dropsie whose Blood and Serum was much diluted could move much more nimbly tho' more seebly than some of a healthful Constitution whose Blood and this Arterial juice was thicker and not so much diluted which doth plainly shew that the thinner the Blood is and the more diluted the Nutritious juice the less quantity of Spirits is required to subtilize it and make it capable of passing into the Fibers It may easily be observed that those People whose Spirits are strong and their Arterial juice very thin are Nimble but the Contractions of their Muscles are not so durable as of those whose Serum is of a thicker Consistence For tho' in the former more of the Subtile Liquor is prepared yet by Reason of its Tenuity it 's sooner receiv'd and carried off by the Lymphaeducts which makes the Contraction shorter Those whose Blood abounds with fixed Salts Phlegmatick Humours which too much dull and resist the Activity of the Animal Spirits are always slow and unapt for Motion whereas if the Blood Acted as a Pondus they must be more nimble and strong because the thicker the Blood is the heavier would be the Pondus As Muscular Motion is many ways vitiated by the fault of the Arterial juice or of the Spirits and consequently by the Distemperature of this subtile Liquor so it is very often depraved and accordingly as the Mass of Blood degenerates from its genuine and proper Nature are produced various Diseases or Symptoms of Diseases viz. Cramps Convulsions Palpitation of the Heart Leaping of the Tendons in Fevers c. for a farther illustration of my Hypothesis before I conclude I will give the Reasons of these Phonomaena When by an Abuse of Non-Naturals the Ferments of the Viscera are perverted and by the faults of the Pancreatick juice and of the Spleen an Acid or Austere Salt is carried forth into a flux presently the Mass of Blood is vitiated The Animal Spirits meeting with this vitious Salt and fermenting in the Glands do there cause irregular Explosions of matter into the Carnous Fibers subtilized in that Fermentation whence follow irregular Contractions of the Muscles Why Convulsive Paroxysms come at uncertain times will easily appear if we do but consider the Procatartick Causes amongst which I shall only mention two viz. The Quantity of Morbisick matter irritating Nature to an Expulsion of it and sudden Passions of the Mind The Quantity of Morbisick matter is far greater in some Bodies than in others before the Spirits are able to recover themselves and to endeavour an Expulsion of it In the former Case Convulsions are Universal and seise the whole Body in the Latter Particular the Morbisick matter being accidentally driven more on one Part than another Again in some Bodies it is sooner heaped up being generated in greater quantities The Matter heaped up at the first is very crude and thick and although it be cast forth into and Circulates through the Musculous parts and continually Ferments with the Spirits in the Glandules yet because it is not sufficiently attenuated to be driven forth into the fleshy Fibers till by frequent Circulations and Fermentations it is exalted from it's state of sixedness to a more Volatile no Convulsions succeed Moreover as long as it continues in its state of Crudity the Animal Spirits are much dulled and their Activity quashed by mixing with it but it being at the length subtilized and rarified by frequent Circulations the Animal Spirits recovering 'em selves and violently Fermenting with it in the Glands carry this Vitious juice explosively into the Fibers The Reason why this Motion is Involuntary is be cause it is not produced by a greater quantity of Spirits flowing from the Brain accordingly as the Pores are dilated by our Appetite but by a mixture of Morbifick and Fermentitious Particles which cause Preternatural Fermentations Expulsions of Matter Attenuated thereby Convulsive sits are sometimes brought on before the Morbifick matter gradually arrives at this state of tenuity when upon sudden Passions of the Mind the Animal Faculties quit their Stations and being over-power'd by external Objects can no longer moderate the Emanations of the Animal Spirits The Formal Cause of the Irregular Emanations of the Spirits in these Convulsions is this the Pores of the Brain being shut up to keep out external Objects heap up the Spirits till by Reason of their quantity the Pores can no longer retain them and then the Spirits rush out quà datur portà in a greater quantity and violently setting upon the Crude juice which they meet with in the Glandules strongly Ferment Attenuate and carry it forth into the Fibers of the Muscles wherein the Spirits are thus accidentally laid down The Brain being thus emptied the Pores are shut up again till the quantity of Spirits make way again and so successively follow Convulsive Motions in this or that Part where-ever the Spirits set upon the Crude Morbisick Matter The 〈◊〉 of the Heart as the 〈◊〉 ed Dr. 〈◊〉 has noted 〈◊〉 proceeds 〈◊〉 Convulsive Motion The Reason why the Morbifick Matter only shews it self in this part and at the same time in no other parts of the Body in this The Mass of Blood 〈◊〉 nated with a Morbifick 〈◊〉 and whatever is the Nature of it since it is 〈◊〉 〈◊〉 the whole Body 〈◊〉 〈◊〉 Rationally expect Universal Convulsions as well as 〈◊〉 But this Morbifick Matter being as yet Crude and not of a sufficient Quantity 〈◊〉 〈◊〉 Nature in all the Parts of the Body these Effects are only produced in this Part where a large Quantity of Spirits is
Contraction of a Muscle When the Contraction ceaseth he thinks that most of the purest Spirits that remain return into the Tendons the other more impure Particles remaining amongst the Fleshy Fibers he fancies that the Fibers of the outward Membrane contracting promote the Retrocession of the Spirits into the Tendons and that for a continual supply of these Liquors the one is always stored up in the Tendons through the Nerves and the other in the Carnous Fibers from the Mass of Blood This Conjecture as it seems ingenious and at the first view very mysterious yet upon a more strict Examination it appears altogether as improbable For to suppose that these Elastick Spirits are laid up and stored in the Tendinous Fibers is contradictory to Reason as well as the Laws of Circulation for since in every Systole of the Brain a fresh supply of Animal Spirits is sent into all the Branches of the Nerves those Animal Spirits in the Tendinous Fibers must needs by a succession of new matter be pressed forwards into the Fleshy Fibres and consequently Accidental Contractions must follow for as much as there are no Valves to hinder their immediate Passage And that there are no Valves nor any thing else to stop the continual Passage of these Spirits may be argued hence because whatever would stop the protrusion of these Spirits when pressed by the Systole of the Brain would also hinder 'em from rushing out of their Store-house though stirred up by an Instinct and so the Muscle would be deprived of Motion But supposing that it were possible for these Elastick Spirits to be stored up in the Tendinous Fibers and that neither their agility and continual Endeavours to explosion nor the force of succeeding Spirits would drive 'em out yet when a Muscle ceaseth from Motion perhaps a Day or Two the Tendon would be so filled and stuffed up that being no longer capable of receiving more Spirits either they must be forced forth into the Carnous Fibers and cause violent and Involuntary Contractions or regurgitating and flowing back upon the Brain would there cause a Vertigo or some other more fatal Disease and besides the Spirits by stagnating so long would be chilled and coagulated and thereby render'd unapt for Motion It is not only absurd to imagine that the Tendons are Store-houses for Spirits but also that they the Instinct being given should cush out of the Carnous Fibers one might as well think that the Contents of the Stomach the Gall in the Vesica Bilaria or the Urine in the Bladder might be excluded by instinct meerly without the help of Muscular Coats or that the Circulation of the Blood might be carried on without the Systole and Diastole of the Heart Moreover to allow that those Elastick Spirits do after this manner rush into the Carnous Fibers when the Instinct is given from the Brain or to speak more properly ad imperium animae either implies that those Spirits which Dr. Willis calls Materiam subtilem are intelligent Matter that they are able to understand the Dictates and Commands of the Soul and to put them in Execution proprio motu or that some Spirits of a Different Nature are at the command of the Soul sent from the Brain which cause the Spirits in the Tendons to be uneasie and by exagitation to expand themselves more powerfully and consequently to leap forth But if neither the texture of those Spirits which as Dr. Willis says give the Instinct be changed and different from those in the Tendons nor the Subtile Matter be Intelligent there would be no Explosion or leaping forth of the Spirits out of the Tendons either by instinct or the accession of new Matter from the Nerves except as I noted before the Spirits which filled the Tendinous Fibers were driven and successively forced out by a fresh supply of Spirits sent in by every Systole of the Brain and so Muscular Motion would not be Voluntary but Accidental That this Matter is not Intelligent is proved sufficiently because to allow that this acts as it receives Instinct from the Brain is to allow a subordinate Soul which acts proprià facultate in every Tendon which is false for an Intelligent Faculty in a Tendon which must act according to the Dictates of the Principal Soul cannot be supposed to be a Faculty of that Soul no more than the Soul of a Disciple Juratus in Verba Magistri and who exactly follows the Dictates of his Master can be said to be a part or faculty of his Master's Soul That no Spirits of a different Nature from those he supposes to be in the Tendons can be transmitted from the Brain is evident For since the same Spirits are distributed through all the Nevervous Channels from the same Fountains the Brain or the Spinal Marrow whatever causes the Spirits to leap out of one Tendon would cause the same Effects in all and all the Muscles must be contracted at the same Instinct Having thus confuted the Grounds and Foundation of his Hypothesis it 's not irrational to expect that the whole Superstructure should fall I shall only further take notice First That if Active Principles of another Nature were heaped up in the Fleshy Fibers by degrees they would be so stuffed and swelled up that there would be no room for the entrance of Elastick Spirits from the Tendons but they themselves would rather by reason of their quantity be forced into the Tendinous Fibers Secondly That it would be absurd to imagine how these Two Spirits after so intimate a commixture as would be produced by a strong Fermentation can be so easily separated that the one should suddenly run back into the Tendons leaving the other behind in the Fleshy Fibers For when Two Liquors of a different Nature and whose Minute and Subtile Particles have a different Motion are mixed together by a mutual Fermentation is produced so intimate a mixture that it is impossible to separate the one from the other sincere because by a mutual collision of different Particles both must needs in some measure be altered and degenerate from their Pristine State so that if the purest part of these Spirits remaining should run back into the Tendons they would be disagreeable to and different from those purer Spirits sent from the Brain and would infect the Store-houses with such a fermentative taint that as new supplys were laid down by the Nerves fresh Explosions and Contractions of the Muscles must follow Thirdly To help the Retrocession of these Spirits into the Tendinous Fibers Dr. Willis would have the Fibers of the investing Membrance to contract But I should rather think that they would contract at the same time with the Muscle if the Instinct were carried through the same Nervous Channels with the Spirits because as he says they are first laid down in the Membrane and thence conveighed to the Tendon Mr. Cowper in the Introduction to his Myotomia Reformata suspects that
said unfermented Succus Nutritius which Liquor thus compounded and prepared is driven by a Succession of Matter through its proper Passages into the Cavities of the Fibrous Cells the remaining and more crude Part of the Succus Nutritius being received together with the Blood and carried back to the Heart This Liquor after this manner conveighed to the Cavities of the Fibers does as it passeth and is thrust through according to the continual Laws of Circulation give nourishment to the Parts and is thence received by the Lymphaeducts Thus I conceive it is continually prepared in the Glandules and Circulates through the Carnous Fibers of all the parts of the Body whilst Motion ceaseth in a moderate quantity so that the Lymphaeducts are capable of receiving it and thereby prevent the Praeternatural Repletion of the Fibers To prove what I have hitherto said besides the Verisimilitude the thing carries with it I could bring many Arguments to illustrate and to make it appear more Plausible and Evident but for Brevities sake and to prevent unnecessary Repetition I shall omit 'em here because they are to be Mentioned hereafter I have given a breif Account of the Structure of a Muscle as far as relates to my Hypothesis and the Use of the Parts as they serve to Nutrition I now proceed to the Efficient Causes of Muscular Motion both Voluntary and Involuntary and first of the Reason of Voluntary Motion That Voluntary Motion does depend upon the Dictates of the Soul and is the Result of it's Faculties but more immediately of our Appetite is sufficiently Evinced because it 's instantly perform'd according to our Will Where the Soul is lodged how and after what Manner it Operates and what it is is most difficult to determine and is not designed for our present enquiry But as it comes under the Consideration of the Brain and it's appendages I shall defer my Thoughts of that till I have a further Opportunity In the mean time That neither the Soul nor any of it's Faculties are the immediate Causes of Muscular Motion but Operate by the Mediation of the Animal Spirits will appear from what follows concerning the Reason of Voluntary Motion And that the Office of the Will is only to open and shut the Pores of the Brain by an Organical Motion as necessity requires what this Motion is and how it is performed and after what manner the Dictates of the Soul and of its Faculties are put in Action is reserved for its proper Seat After what manner soever the Soul exerts it's Faculties and directs that Subtile Matter the Animal Spirits which is sent through the Branches of the Nerves in greater or less quatities according to our Appetite to this or that Part it is allowed that when our Body ceaseth from Motion and all our Voluntary Faculties are at quiet the Pores and Passages of the Brain leading to the Instruments of Voluntary Motion are locked or closed up And then I suppose that the Spirits moderately flowing into each Muscle do prepare so much of the Subtile Liquor aforemention'd as is sufficient to Nourish the Parts as it passeth through ' em But when the Pores of the Brain are opened and unlocked the Animals Spirits forced by a continual Succession of Matter flow into all the Branches of the Nerves more plentifully and being laid down in the Glandules raise a stronger Fermentation by which means a greater quantity of the Subtile Liquor is prepared and forced into the fleshy Fibers more copiously and rather faster that it can be received and evacuated by the Lymphaeducts so that the Fibers being all equally swelled with its quantity consequently Contract the Muscles which is the Cause of a Tonick Motion When these Animal Spirits are by a pressure and Systole of the Brain and succeeding Spirits sent yet more plentifully into the Nervous Channels leading to the Muscles to be Contracted than into those which are in Motu Tonico or into the Antagonists the Passages and Pores leading to those Nerves being yet more expanded and opened there is a greater quantity of the Subtile Liquor prepared in the Glandules and thrust out into the Carnous Fibers and their Cells being more swelled and dilated consequently there follows stronger and more violent Contractions of the Muscles whence proceeds Local Motion By the Systole of the Brain I don't mean any other Motion than what proceeds from the Pulsation of the Arteries distributed through that Part. That this motion only proceeds from the Pulsation of the Arteries implies that it is stronger drives the Spirits through the Brain into the Nerves with greater force than if it were really the Motion of the Brain it self the Heart from whence the Pulsation of the Arteries proceeds being a stronger and more compact Part as to its Substance than the Brain If it be asked why this Subtile Liquor is not more easily forced into the Venous Ducts than into those that lead to the Fibrous Cells because the former are larger I Answer That the Venous Ducts are so proportioned that they might not be capable of receiving all that is laid down by the Nerves and Arteries on purpose that some Subtile Parts might be continually driven into the Fibrous Cells and when by a more copious Influx of Animal Spirits a stronger Fermention is raised in the Glandules presently the Contents swell up and are expanded so that the Veins being not able to receive them as before more of that Liquor is not only subtilized but forced into the Fibers As soon as according to our Appetite the Pores of the Brain which conveigh Spirits to the Nerves leading to the Contracted Muscles are shut more closely up again and leave of to be dilated the Animal Spirits cease to flow more into the Musculous Glandules than are required to Subtilize and prepare a sufficient quantity of Nourishment for the Fibers as in the Antagonist then presently the Contraction ceaseth to be carried on and the Superfluous Liquor heaped up in the Fibers is evacuated by the Lymphaeducts Here perhaps because I said in the foregoing Paragraph the Liquor heaped up in the Fibers is Evacuated by the Lymphaeducts it may be a Question whether this Liquor does all the time a Muscle is Contracted constantly flow through these Cells into the Lymphaeducts or whether it remains in the Cells till Motion is to cease and is not evacuated by the said Ducts till then I say it does continually run of by the Lymphaeducts constantly all the time a Muscle is Contracted Otherwise since as long as Spirits are directed in a competent quantity to the Contracted Muscles to keep up the Dilation of the Fibers they would presently be incapable of receiving it and it must needs Regurgitate as it was prepared and in a great Measure disturb Circulation But to prevent many absurd Consequences if it should remain in the Cells so long I affirm that it is constantly forced forward by a Succession of Matter and as it is forced into
and Circulates through these Cells in greater or less quantities so Contractions are stronger or weaker or not at all the Fibrous Cells being accordingly Distended Dilated and Contracted in Longitude and when according to our Appetite this Liquor ceaseth to flow into the Fibers in so great a quantity as to Contract the Muscle that matter which before dilated the Fibers is Evacuated as being Superfluous Nourishment so that for the future it runs through in a moderate quantity as before Contraction till their Repletion is again renued to Reiterate Motion If it be asked why this Liquor is not as easily forced backwards out of the Fibrous Cells into the Glandules from whence it came as into the Lymphaeducts and so think there would be no need for Lymphaeducts I answer That if there be no Valve at the inward Orifice of every Duct to hinder its reflux which would be no absurdity to conclude for we see always upon the like occasion Nature hath furnish'd such Places with Valves yet I say if there were none the direct Motion of subsequent Matter from the Glandules would sufficiently hinder the reflux of it and since its reflux is opposed by new matter forced successively after it and since according to the course of Circulation the Matter driven into the Lymphaeducts before it will give way for its expulsion it would be more reasonable to imagine that the matter contained in the Fibers is evacuated qua datur porta rather than qua non datur for when we design the Relaxation of a Muscle though the Liquor successively sent from the Glands does not press forwards altogether as forcibly and in as great Quantities as whilst Contraction is continued yet it follows moderately so as to oppose the Retrocession of any thing I mean moderately as to its quantity for the continual violent concourse of the Animal Spirits and Arterial Blood drive it then into the Fibers almost as violently as when the Muscle is contracted That these Lymphaeducts do thus receive this Subtile Liquor and that for that end they are inserted into the Fibrous Cells I am perswaded because it cannot otherwise be understood how the Matter that stuffs them up and causes Contraction could be drawn out again without a Retrocession through the same Channels by which it was brought in And though the most Learned and Famous Dr. Willis Dr. Ridley and others do allow a Retrocession yet since it contradicts the course of Circulation we must either deny Circulation or reject their Opinions Besides I cannot conceive what other occasion there is for Lymphaeducts in a Muscle since whatever is brought by the Arteries might as well be returned by the Veins as by two sorts of Vessels But for as much as Nature hath made nothing in vain and since there is so great necessity that they should be inserted into the Cells I think it not irrational nor absurd to conclude they were designed for the afore-mentioned end That we may understand a little better the Nature of this Liquor which we have so often mentioned let us consider a little more fully how that Fermentation is carried on in the said Glandules It 's commonly known that when a Ferment is put to a Mass whether Liquid or of a solid consistence whatever is the nature of the Ferment it according to its power always endeavours to render whatever comes within the Sphaere of its Activity as like it as possible So in these Glandules the Animal Spirits fermenting with the Arterial Juice and the Nature of 'em being according to Dr. Willis and Diemerbroeck Spirituo-Saline composed of Volitile Salt and Sulphur they by Reason of their absolute Quality more readily mix with the crude Sulphureo-saline Particles of the Nutricious Arterial Juice and as they are more or less in quantity so they exalt and carry forth into a Flux more or less of that Crude Sulphureo-saline Mass which being by Fermentation subtilized is diluted with a sufficient quantity of Lympha or the watry part of the Serum of the Blood and the Liquor resulting from that Composition is thrust out into the Fibrous Cells That this Lympha might be thin enough to dilute the said Liquor sufficiently it is much attenuated in that Fermentation That there is such a Fermentation that the Nerves are inserted into the Glandules and lay down Animal Spirits as the Principal Cause of that Fermentation that the Arteries lay down Blood together with the aforemention'd Juice and that in those Glands a subtile Liquor is prepared being composed of Animal Spirits and the most rarified parts of the said Succus that neither the Arterial Juice nor the Animal Spirits simply can cause the Contraction of a Muscle but furthermore that it is necessary that this Subtile Liquor should be so prepared and composed as being capable to enter into the Fibers and to contract the Muscle is sufficiently apparent from what hath been said and will more clearly be evinced by what follows And first if there be a Communication of these Vessels as certainly there is then it must needs follow that there is a commixture of their Contents if there be a commixture of their Contents then there is a Fermentation and in that Fermentation it must needs follow that the Animal Spirits will according to their Energie and Activity Subtilize and Attenuate the Crudest Parts of the Arterial juice By a mutual Fermentation there must needs be implyed an intimate Commixture and the Result of that Commixture must needs be different from the Animal Spirits or Arterial juice simply before they are mixed so that the Liquor resulting from the Mixture of 'em may be properly called a Subtile Liquor And accordingly as the Animal Spirits are more or less in quantity to mix with the Arterial juice more or less will be prepared and thrust out into the Fibrous Cells and consequently the Fibrous Cells must be more or less Tumified and the Muscle Contracted as more or less Spirits are laid down in the Glandules So that all I have to Prove is That neither the Arterial juice nor the Animal Spirits can cause the Contraction of a Muscle and then it will follow consequently that there is a Communication of these Vessels and for that end in the aforesaid Glandules It hath often been found that an Atrophea of the Parts will follow the Relaxation a Palsie the Abscission or Ligature of the Nerves leading to those Parts Which sufficiently shews that the Arterial juice it self cannot cause the Contraction of a Muscle without the assistance of the Animal Spirits because when the Animal Spirits cease to flow into the Glandules for want of a dew Fermentation to Subtilize and Prepare a sufficient quantity of the Arterial juice the Carnous Fibers are not only deprived of necessary Recruits and Alimental refreshment so that they must needs waste away and grow Languid but also for want of a sufficient quantity of the Subtile Liquor to distend the Fibrous Cells
they become destitute of Motion That the Animal Spirits simply cannot cause the Contraction of a Muscle is proved because by a Ligature on the Descending Trunk of the Aorta the Inferior Parts become destitute of Motion For tho' the Influx of the Animal Spirits be not hindered yet for want of Arterial juice the matter requisite for the Composition of this Subtile Liquor is not laid down in the Glandules and the Muscles the Instruments of Motion cannot Contract without an Efficient cause From what is contained in these two Paragraphs it appears that neither the Animal Spirits nor the Arterial juice simply can cause the Contraction of a Muscle because when the Animal Spirits are hindered to flow into the Glandules to Subtilize and prepare the Arterial juice it is not thin enough to be driven out into the Fibers And tho' when the Influx of the Arterial juice is hindered the Spirits are permitted to flow in yet by Reason of the small quantity of 'em they run through the Fibers without distending ' em That this Arterial juice ought not nay cannot pass into the Fibrous Cells till subtilized and prepared by the Fermentation in the Glandules is Plain because if it could they wou'd be stuffed up with the quantity of it driven in by the continual course of Circulation so as to Contract the Muscle against our Will which is otherwise Now since the Arterial juice cannot pass into the Fibers till Subtilized and since the Animal Spirits are not enough in quantity moreover since neither of 'em simply are capable of Contracting the Fibers and if either be obstructed the Action is abolished I say since it is an Action that depends upon the mutual Assistance of each it is apparent That it must be performed by a Liquor resulting from a Mixture of both And then we must of Necessity allow a Communication of these Vessels else there could be no mixture of their contents and the Arterial juice must be prepared before it can be forced into the Fibers for the Reasons beforementioned to which end it will be necessary that the Vessels terminate in the Glandules That their Contents may be mixed and that this Subtile Liquor resulting from a Mutual conflict of the Animal Spirits subtilizing the cruder Arterial juice by Fermentation in greater or less quantities accordingly as the Spirits are laid down by the Nerves may be prepared and made ready to be driven into the Fibers To promote the Fermentation and the Preparation of this Subtile Liquor the forcible influx of the Animal Spirits and of the Arterial Blood much conduce For be the Temper of the Arterial juice and of the Animal Spirits never so good unless they are driven violently one against another there would be required a longer time before they could be so mixed and fermented as they ought but the succession of new Matter admitting no long delay it is requisite that they should be thus forcibly driven in together to the end that the Spirits might be diffused through the whole Mass sooner and that their Minute Particles striking more violently against the fixed and compacted Particles of the Blood might more immediately break and separate the strict Union of its Parts and by a violent Fermentation sufficiently dissolve and volatilize 'em in so short a time as the Continual Pulsations of succeeding Humors admit The violent concourse of the Blood and Spirits do not only promote this Fermentation and the separation of the Subtile Liquor but also successively force the Matter prepared and separated into the fleshy Fibers This is so highly Probable that it needs no Arguments to make it more Evident it being the unavoidable consequence of a continual Circulation Now I have given the Reasons of Voluntary Motion and the Efficient Causes of the Contraction of a Muscle it will be easie to unfould the Reason of Involuntary Motion That Voluntary Motion depends upon the Will is manifest and that Involuntary Motion is not at all Subject to it but is performed not only without the Dictates of our Appetite but against 'em is so evident that it would be superfluous and useless to dispute it I shall only shew how it is performed which is indeed a little more obscure As Voluntary Motion is perform'd for as much as the Pores of the Brain are dilated according to our Appetite so that the Animal Spirits flow more plentifully into the Glandules and prepare a sufficient quantity of the Subtile Liquor to distend the Fibers as it passes through 'em so those Pores which lead to the Nerves serving to Involuntary Motion are proportioned in such a manner that they continually conveigh Animal Spirits in a sufficient quantity to cause a perpetual Motion These Pores being so proportioned there is no need that they shou'd have such an Organick Motion as those serving to the Instruments of Voluntary Motion because since they are proportioned so as to carry Spirits in a competent quantity there is no necessity that they should be either Dilated or Contracted To Prove that these Pores do lay down a competent Quantity of Spirits to be carried to the Glands I need not bring many Arguments for its plain and evident to all Practitioners in Physick that when the Spirits are too much carried forth and exalted as in a Diary Fever the Pulse is strong and vehement and by a too great exagitation of them it becomes more quick and frequent it is also Evident that when the Animal Spirits are depressed the Pulse is Weak Slow and Rare as most commonly in Women subject to Hysterick Fits and when the Spirits by an Acute or Cronick Distemper are worn out and almost spent the Pulse is either Vermiculans Formicans or Tremens which are signs that Nature is almost spent and ready to yield to the Distemper I say this is evident enough it is then beyond Contradiction that a healthful Pulse depends upon a moderate Quantity of Animal Spirits and that they continually flow into those Nerves leading to the Instruments of Involuntary Motion and as their Quantity varies so more or less of the Subtile Liquor is prepared to distend the Fibers of those Muscles When the Spirits are weak or almost spent there must needs flow a less quantity into the Glandules and when they are exalted a greater and if Extremes either frustrate Natural or cause Preternatural Effects we may not only conclude that Natural Actions are performed by a moderate Quantity but from hence we may bring good Arguments for a further proof and confirmation of my Hypothesis about Voluntary Motion Since I have said that the Spirits by Reason of a particular Proportion of the Pores flow continually in a just Quantity and that these Pores are not subject to be Dilated or Contracted according to our Appetite it remains that I should shew how it comes to pass that the Systole of the Heart is interrupted with such constant Diastoles whereas when the Pores serving to Voluntary Contractions are
continually laid down to serment with it by which means it is Subdued in this part before it arrives at such a State of Activity of such a Quantity as to cause irregular Fermentations and Contractions in other Parts In a 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 The Muscles continue constantly contracted against our Appetite these Distempers seize People whose Blood is rather of a Vitriolick Tenacious Nature and impregnated with more Fermentative Spirits so that by reason of the Viscidity of the Matter violently forced into the Fibers either the Lymphaeducts are obstructed or by reason of a continual Fermentation Matter gradually succeeds In the Cramp the Fermentation is different from that which is Natural or in other Convulsive Motions that which is Natural being caused by the Animal Spirits preparing a Subtil and Homogenious Liquor In other Convulsions the Animal Spirits ferment with and endeavour to subdue a Morbisick Humour brought and layed down by the Arteries and the Matter thus attenuated is accidentally forced into the Fibers But these are caused by the continual Conflict of the Volatile Animal Spirits strongly fermenting with Fermentative and Elastick Particles of another Nature supplied by the Mass of Blood where both striving to subdue each other the Elastick Particles of the Blood more strongly oppose the Motion of the Spirits and the Spirits them by a contrary agitation and intestine Motion of their Particles and these Two being violently exploded and impetuously leaping into and fermenting in the Fibers cause most strong and painful Contractions The Subsultus Tendinum in Fevers are caused when the Spirits being too much exalted leap irregularly out of the Brain and raise the Fermentation in the Glands so high as to prepare and carry too much of the Subtile Liquor into the Fibers which because it is so very thin easily slips into the Lymphaeducts and makes the Contraction short I shall add the Reason only of one other Phaenomenon which seems more evidently to prove that Muscular Motion depends on the greater influx of Animal Spirits viz. Why the Contraction of one Muscle followeth when the Antagonist becomes Paralytick as in Spasmus Cynicus The Branches of the Nerves being derived from the Brain when the Influx of the Spirits into the Muscles of the one side are hindered they regurgitate and are driven presently in a greater quantity into the Antagonist as by the Loss of one Eye the other by a greater Influx of Spirits becomes more Acute This is evident and needs no further proof Thus I have laid down my Hypothesis of the Formal and Efficient Causes of Muscular Motion and how it is vitiated or depraved which I the more willingly commit to the Judgment of Learned and Competent Judges with due Submission because it seems to me to answer Natural Ends and to account for the several Phaenomena without the Difficulties Enormous Motions and Impossibilities which usually attend Hypotheses on this Subject not doubting but it will give satisfaction till one more probable and plausible shall succeed FINIS Books lately Printed for and Sold by A. J. Churchill at the Black Swan in Pater-Noster-Row A View of Universal History from the Creation to the Year of Christ 1695. wherein the most memorable Persons and Things in the known Kingdoms and Countries of the World are set down in several Columns by way of Synchronism according to their proper Centuries and Years By Francis Tallents sometime Fellow of Magdalen-Colledge Cambridge The whole graven in 16 Copper-Plates each 15 Inches deep and 22 broad bound up into Books the Sheets lined A Work of great Exactness and Curiosity Price 16 s. A Compleat Journal of the Votes Speeches and Debates both of the House of Lords and Houses of Commons throughout the whole Reign of Queen Elizabeth Collected by Sir Simonds Dewes Baronet and Published by Paul Bowes of the Middle-Temple Esq The 2d Edition Fol. The Works of the famous Nicholas Machiavel Citizen and Secretary of Florence Writen Originally in Italian and from thence faithfully Translated into English Fol. Mr. Lock 's Essay concerning Humane Understanding The Third Edition with large Additions Fol. His Thoughts of Education Octavo The Fables of Aesop and other Mithologists made English by Sir Roger L'Estrange Kt. Fol. Two Treatises of Government the first an Answer to Filmer's Patriarch The latter an Essay concerning the true Original Extent end of Civil Government Oct. Notitia Monastica Or A short History of the Religious Houses in England and Wales c. By Thomas Tanner A. B. Octavo The Resurrection of the same Body asserted from the Tradition of the Heathens the Ancient Jews and the Primitive Church With an Answer to the Objections brought against By Humphry Hody D. D. Bishop Wilkins of Prayer and Preaching Enlarged by the Bishop of Norwich and Dr. Williams Octavo Sir William Temple ' s History of the Netherlands Octavo Miscellanea Octavo Dr. Patrick's New Version of all the Psalms of David in Metre Twelves Two Treatises of Natural Religion Octavo Gentleman's Religion with the Grounds and Reasons of it In which the Truth of Christianity in general is vindicated its Simplicity asserted and some Introductory Rules for the discovering of its particular Doctrines Precepts are proposed By a Private Gentleman Sermons Preached by Dr. R. Leighâ—on late A. Bp of Glasgow Published at the Desire of his Friends after his death 〈◊〉 his Papers written with his own Hand The Second Edition 〈◊〉 The End The Usefulness of Muscular Motion as it tends to the maintenance of life With respect to the Soul and its Functions A Muscle is a Noble part Dr. Willis's Opinion examin'd No Elastick Spirits laid up in the Tendons Nor instinct sent from the Brain because Either it implies that the Spirits are Intelligent Or that Spirits of a Different Nature are sent from it The Matter is not Intelligent No Spirits of a different Nature are sent from the Brain No active Principles heaped up in the Fleshy Fibers Nor retrocession of subtile Matter into the Tendons Mr. Cowper's opinion examined The Blood does not act as a Pondus The First Argument A Second A Third A Fifth A Sixth Dr. Ridley's Opinion examined The common Postulatum is not to be allowed There is no Retrocession of a Fluid from the Autagonist Nor is it forced out so as to cause a Vacuum Of the Structure of a Muscle The formal cause of the contraction of a Muscle Vessels implanted into a Muscle Their distribution And terminations in small Glands Proved What a Gland is Why they cannot be discerned The Use of the Nerves And Arteries inserted in the Glands To prepare a Liquor different from the Spirits or Succus The Use of it The Reason of Tonick Motion Objections Answered The Use of the Lymphaeducts The Nature of the Liquor consider'd and the manner of its preparation By Fermentation Proved The Arterial juice simply cannot cause the Contraction of a Muscle Nor the Animal Spirits Because the Arterial juice cannot pass into the Fibers till prepar'd by the Spirits The Reason of Involuntary Motion Proved How it comes to pass that the Systole of the Heart is interrupted with such frequent Diastoles Why the Muscles serving to Respiration are subject in some measure to our Appetite Why old People are subject to a trembling of their Head or Hands Another Phaenomena Explained A Third A Fourth A Fifth A Sixth The Reasons of Convulsions 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 Of the Cramp Of the Subsultus Tendinum in Fevers Of a Spasmus Cynicus
the same time being driven back with an equal speed from the Antagonist Muscle into the room of the former which was transmitted from the Brain to the Contracted Muscle to avoid a Vacuum That the Nervous Ducts as well as Carnous Fibers are always Watered with a Fluid and that the Nervous Liquor equally flows into the Branches of all the Nerves according to their Proportion is beyond Contradiction but if we allow the common Postulatum we must also conclude That the Animal Fluid is Intelligent and there will follow the same Difficulties as were before mentioned about the leaping forth of Spirits out of Dr. Willis his Tendinous Receptacles where I have given sufficient Reasons to reject this Postulatum as Impossible Moreover if it were Possible for so much of this Animal Fluid as is requisite to distend the Carnous Fibers to be conveiged in so short a time as Muscular Motion follows our Appetite through the small Branches of the Nerves yet it would be altogether unconceivable how it should flow back from the Antagonist thus contrary to the Course of Circulation but the Reason he gives is partly this to avoid a Vacuum This is a most Stupendious sort of a Motion at the same time that the Liquid is forced into the one Muscle it runs directly opposite from the Antagonist which is very irregular and unlikely Besides I cannot understand how it comes to pass that the Animal Fluid is so much forced out of the Branches of the Nerves leading to the Muscles to be contracted as to leave a Vacuum for the Reception of Liquids from the Antagonist but if an Emptiness or Vacuum could be so made the Fluids would as soon be drawn back again out of the Muscles into which our Appetite directed them to fill that empty Space as out of the Antagonist To prevent an Objection against his Supposition that the fluid runs back again from the Antagonist he thinks he has answered it already but very insufficiently He says if it be said that the Reflux is opposed by the constant direct Motion it 's easie to reply that it 's slow direct Motion is easily repelled by the violent impulse of the forcibly relaxed Muscle I must confess it 's no piece of difficulty to make such an Answer but the Reply seems not so easily to give satisfaction I would fain know how the Antagonist comes to be so forcibly relaxed as by a violent impulse to overpower the direct Motion For the direct Motion cannot be so weak as to be easily overcome and since the Animal Fluid as he calls it is continually driven by the Pulsation of the Heart through the Brain or Spinal Marrow into the Nerves whatever repells the direct Motion must be of equal if not greater force than the Systole of the Heart He begs leave to ask how when another bends his Arm against his Will the Muscles become tumid as when voluntary contracted This Question doth not at all confirm his Hypothesis but on the contrary pleads against it It doth not confirm it because he doth not account for the Phaenomenon nor give a Reason agreeable to his Opinion but leaves the thing barely without explanation it pleads against him because according to his Opinion the Muscle instead of growing tumid ought violently to relax at least to endeavour a relaxation and not contrary to the Appetite to run into a Muscle against our Will For he says at the same time that the Muscles to be contracted grow tumid the Antagonists by a violent relaxation drive out the fluid contained in them So that it will follow that at the same time we endeavour to keep our Arm unbent by striving to keep the one Muscle contracted at the same time we ought to endeavour a relaxation of the Antagonist and though that force which bends our Arm doth resist the Voluntary Contraction of the Muscle yet there would nothing hinder the voluntary Relaxation of that Muscle which is the Antagonist but the slow direct Motion as he calls it But here I humbly take leave to ask whether there is not a great deal of difference betwixt a Muscle that is thus tumid and one that is Contracted For altho a Muscle cannot but be tumid when contracted yet it may be tumid though not contracted I mean as it is in Muscular motion I have indeed oft taken notice that when my Arm has been bent against my Will the Muscles become tumid but not as in Muscular Motion for when a Muscle is Voluntarily contracted it 's hard and tumid but when my Arm is bent against my Will it 's far more soft and though tumid yet very little contracted Since the Reason why the Muscles grow thus tumid cannot be accounted for by this Hypothesis I shall explain it hereafter Having thus examined and I hope confuted the aforementioned Opinions I shall in the next place briefly consider the Fabrick of a Muscle the immediate Instrument of Motion Anatomists describing the Fabrick of the Muscles of the Body divide 'em into Simple Compound and more Compound as also every Muscle into Three Parts the Head the Belly and the Tail they acquaint you how the Belly is composed of several Fasciculi of Fleshy Fibers which lie parallel to each other c. of which enough may be seen with a full Description of each sort of Muscles in the Original Authors I shall omit the Repetition here and only take Notice of it's Fabrick as far as relates to my Hypothesis Every Muscle is endowed with opposite Tendons which are composed of several Fasciculi of Fibers lying parallel to each other These Fibers being strictly joyned together compose a strong tenacious and firm Tendon but being separated one from another are more fragile and subject to be easily broke and pulled in pieces they are continued from each Tendon to it's opposite The Interstices of the Fibers thus separated are filled with the Branches and Extremities of Vessels the major part of which are Sanguiferous so that the Fibers continued through the Belly of a Muscle being obscured by the colour of the Blood seem to degenerate from the Tendinous Fibers and therefore are called Fleshy These Fibers as they are continued from each opposite Tendon so also there is a continued Cavity from one end of Every Fiber to the other which being partitioned by several transverse and perforated Membranes every Fiber according to Dr. Croone resembles a continued Series of Bladders opening one into another By an Intumescence of these Fibers they are contracted in length and by a Contraction of their Longitude each Tendon is drawn nearer to its opposite which is the formal cause of Muscular Motion as far as can be made evident by Autopsie This is so unanimously assented to and so apparent to the naked Eye that it requires no further proof As for the Efficient Causes of Muscular Motion before they can be sufficiently shewn we must enquire how many sorts of Vessels are implanted into
each Muscle which according to Anatomists are Four Nerves Arteries Veins and Lymphaeducts the Nerves and Arteries furnish the Muscles with Spirits and Blood the Veins and Lymphaeducts carry back the superfluity of Blood and Lympha The Branches of all these Vessels are minutely distributed through the whole Muscle and by an intermixture and texture of the most Minute and Subtile Branches of the same is formed that Substance which fills up the Interstices of the Fibers and which denominates the whole Belly of a Muscle Fleshy The colour of these Vessels as of all others is without doubt White but by the Contents of the Sanguiferous Vessels the whole Belly of a Muscle is coloured Red. The Terminations of these Vessels are so minute and small so brittle and subject to be broke that it 's as difficult to trace and find their Terminations and Insertions as to divide a Hair into an Hundred Parts and though many things are made visible by the help of Microscopes which are otherwise too subtile to be discerned and discovered by the naked Eye yet I am not without Reason perswaded that the terminations of these Vessels cannot be perceived by the help of a Microscope Some indeed whatever they think is probable lest it should not be credited presently strenuously affirm they saw it with their Microscopes and so easily impose on those that less inquire after truth themselves but take it on trust from others and perhaps prevent those not so exquisitely skill'd in Microscopes from making any further search after truth I shall not here say that what I propose concerning the Terminations of these Vessels was seen with any Microscope but shall declare my Opinion in this Matter too subtile for any Microscope but Reason It being impossible for any one to understand the true Reason of Muscular Motion unless first acquainted with the distribution of these Vessels and their Contents first I conceive that as the Nerves Arteries and Veins are all distributed through a Muscle so it is but Reasonable to conclude that their minute and subtile twigs are all before they terminate interwoven and mixed with one another And if so it will not be absurd to imagine that they all end as it were in small and Diminutive Glands And if the ends of the Vessels be so small that their terminations cannot be perceived by a Microscope these Glandules composed of the Invisible ends of the aforesaid Vessels must needs be very small and fine and consequently may not be perceived by the help of extraordinary Microscopes From these Glandules thus formed are derived short Ducts or Passages for the conveyance of a subtile Liquor out of the aforesaid Glandules into the Cavities of the Carnous Fibers This Passage very likely may be composed of the external Arterial Coat Into the Cavity of the Carnous Fibers besides these Ducts the twigs of the Lymphaeducts are also inserted to carry back a superfluous Lympha If any one thinks it improper or absurd to assert that these Vessels do thus terminate as if it were in small Glandules let him but consider what a Gland is and how it is composed and he will not think the Conclusion irrational For a Gland is nothing else but a Composition of an Infinite Number of small and diminutive Vessels several and most of which have Communication one with another which Gland so composed is as a Store-house to receive and contain a certain Liquor till necessity requires or its quantity causes an exclusion of it And this seems plainly to be favour'd by Dr. Ridley when he says that the whole Body is a continuity of Vessels ad infinitum Now if a Gland consists of an infinite Number of small Vessels and if the Branches of Nerves Veins and Arteries be divided before they terminate into an innumerable number of most invisible twigs as is most certain when from one twig of each sort is derived a vast number and all these so derived are mixed and interwoven one with another why may we not say at least Metaphorically since they in their Distributions imitate the Composition of Glands that they terminate in small Glandules Some perhaps will ask how must we discover these Glands Malpigius hath observed the Liver to be composed of Clusters of Glands hanging at the Extremities of the larger Vessels like so many Bunches of Grapes and the Glands in other parts are apparent but in a Muscle we can discern no such things for it especially when boiled parts into distinct Carnous Fibers To which I Answer That those Glands are nothing else but a Composition of the ends of importing and exporting Vessels and the Reason why we cannot discern the same in a Muscle is this because the Extremities of the Vessels are so fine and consequently so brittle and are contained in the Interstices of so strong and firm Fibers that whenever we endeavour a separation of the Fibers the Glandules are torn away from the Vessels from which they are derived whereas the Fibers which run transverse the Liver easily crumble away being much more weak and less Numerous The Reason why the Muscular Fibers are so much stronger than those that run through the Liver is apparent enough Viz. because the former are the Instruments of Motion and consequently there lies a greater stress of them than on the latter which serve to make the Part a little more compact and to keep the outward Coat from being loose upon it's Circumference Now because it is impossible to separate and remove these Muscular Fibers so as to leave the Sanguiferous Vessels as entire as would be requisite for the exact and certain discovery of their Terminations and because it is certain that these Vessels are divided and subdivided ad minimum that they are interwoven one with another and that a Gland is nothing else but a Composition of Vessels we may rationally conclude they all Terminate in Diminutive Glands The Nerves Veins and Arteries composing and ending in these Glands I shall next Enquire to what end they do all thus meet together The Use of the Nerves in these is the same as in other Parts Viz. to conveigh a Spirituo-saline Liquor from the Brain Which Spirits being Volatile and apt to Ferment when mixed with a Liquor of a contrary Nature are continually sent by the Systole of the Brain into all the Muscles of the Body and being laid down forcibly in the aforesaid Diminutive Glands do there meet with Arterious Blood driven in by every Contraction of the Heart Which two Liquors strongly fermenting together the Animal Spirits do by an Attrition Subtilise Attenuate and Rarifie those Particles of the Succus Nutritius supplyed from the Mass of Blood by which Means their own are much dulled and become less Active for the future and by a Mixture of these Animal Spirits with the rarified Succus Nutritius results a Liquor Different from and of a middle State betwixt the Animal Spirits and the