AN ESSAY, TOWARDS A DEFINITION OF ANIMAL VITALITY.

IT is an apparent paradox, but it is not therefore the leſs true, that thoſe ideas, or phenomena, that are moſt fami⯑liar to us, ſhould frequently be the moſt difficult to explain. This is particularly the caſe with the ſubject of the preſent Eſſay.

Life is a term ſo conſtantly recurring, and, indeed, as one would at firſt ſuppoſe, an image ſo perpetually preſenting itſelf to our ſenſes—and the difference is ſo ſtriking, between the pale inſenſate corpſe, and a living being, with all the expreſſions, actions, and attributes with which, in the higher ſcale of animals, he generally offers himſelf to our [6]eyes, or our imaginations, that a vulgar obſerver would ſneer at the philoſopher who ſhould ſuggeſt the difficulty of aſcertain⯑ing in what vitality conſiſts: yet where is the ſtudent, who, upon ſerious examination, has found himſelf ſatisfied with any thing that has been ſaid upon the ſubject?

Does not the greateſt anatomical philoſopher, even of the preſent enlightened age, tacitly confeſs the confuſion of his ideas in this reſpect, when he declares that, ‘"From an exa⯑mination and ſurvey of animal matter when dead, only we gain an idea of living animal matter;"’ and that ‘"as from life only we gain an idea of death, ſo from death only we gain an idea of life?"’

Before we can poſſibly derive any ſort of information from this antitheſis, it is neceſſary that we ſhould be inſtructed how life and death may be accurately diſcriminated; for how are we to make compariſons between objects which we are unable to ſeparate from each other? But even this has never ſucceſsfully been attempted; for though there are certain ſigns (as putrefaction, &c.) by which the death of the animal may be demonſtrated; yet, as it is not even pre⯑tended that putrefaction is the act of vital diſſolution,—or, in other words, that the body which is not putrid is neceſſarily alive—death muſt have taken place, independently of any ſuch change; and we are, therefore, juſt as much in the [7]dark as ever with reſpect to the ultimate teſt by which the preſence of life may be aſcertained.

Treatiſe after treatiſe has been written on the Vital Prin⯑ciple; theory has pulled down theory without end; and the groſs contradictions which have marked the opinions of the greateſt characters upon the ſubject, might induce one to think that, even with reſpect to the general idea, we are ſtill entirely at a loſs; that we are ſeeking for an imaginary ſome⯑thing—a phantom of the brain, which, perhaps, has no real exiſtence: and, indeed, if the term is to be literally under⯑ſtood—if this Vital Principle is to be conſidered as a diſtinct or independent eſſence, ſeparable from the effects and actions by which the ſtate of vitality is to be aſcertained, I am not ſure that this concluſion will be found to involve as much abſurdity as is included in the contrary opinion.

I am well aware that there are ſome, who, from the firſt bluſh of this obſervation, may be inclined to ſmile, and con⯑ſider it as the ne plus ultra of ſcepticiſm: but the philoſo⯑pher will do well to keep the diſtinction between a vital principle, and the ſtate of vitality, conſtantly in his mind: the former properly meaning a living CAUSE—the latter ſimply a modification or effect, to which the name of life is given, and which may be the reſult of a co-operation of other cauſes, neither [8]of which need, in themſelves, of neceſſity be alive.—In other words, to contend for the exiſtence of a Vital Principle, is to contend that there is ſuperadded to organized matter a diſtinct ſomething, in itſelf alive, by which the vital functions are carried on; while, on the other hand, the State of Vitality need not of neceſſity be conſtrued, as mean⯑ing any thing more than the condition of the animal body during the continuance of thoſe functions.

Now—that there is a ſtate of animal exiſtence, that may properly be called the State of Life, and be put in direct contradiſtinction to that of Death, and that upon the previous induction of this ſtate depend all the higher functions of the ſenſitive being, are certainly among the moſt ſelf-evident of all ſimple propoſitions. Nor is it leſs certain, that there muſt be an exact and preciſe moment (nay, fraction, or, if I may ſo expreſs myſelf, mathematical point of a moment), in which this ſtate of life ceaſes, and that of death begins; though whe⯑ther that moment can ever be aſcertained by any ſenſible and poſitive mark of diſcrimination, is matter of conſiderable doubt: but if this Vitality is to be conſidered, ab origine, as a Principle, (by which, phyſically or philoſophically ſpeaking, I conceive is always to be underſtood, a ſimple, elementary, and firſt natural cauſe), and not, as itſelf, an effect of the co-ope⯑ration of other principles, or natural and pre-exiſting cauſes, [9]I own, for my own part, I muſt be rather ſlow in yielding my aſſent; and, while I bow with reſpect to ſuperior judg⯑ments, muſt claim the prerogative of exerciſing my own.

Egypt, Greece and Rome are, it is true, againſt me:—the ancients and the moderns—Ariſtotle and Plato, Plutarch, Moſes, and John Hunter; and yet againſt this hoſt of Giants I preſume to lift my pigmy lance, and brave the unequal combat.

The moſt ancient of the opinions tranſmitted to us upon this ſubject, I believe, is that of the Egyptians, which con⯑ſiders the Soul (or living Principle) as a kind of ſhadow, or aerial ſubſtance, diffuſed through every part of the body, animating every limb, and partaking of all its proportions.

Man, according to them, conſiſts of three parts—a groſs periſhable body—an intellectual principle, or intelligent mind, by which he is elevated above the brute creation—and an image, or ſoul, exactly reſembling the body in ſhape, in magnitude and feature, upon which animation, and all the functions of the animal frame depend; and in which, alſo, they conceive the intellectual principle to be enſhrined.

That theſe were conſidered, in the proper meaning of the word, as diſtinct principles, is evident, ſince they are treated as being capable of independent exiſtence—the ſoul, or vital principle, continuing many of its functions after its ſepara⯑tion from the body; and the mind, or intellectual power, after the final ſeparation, being ſometimes conſigned to a different reſidence from the ſoul.

This opinion (which ſtill, with ſome ſlight variations, con⯑tinues to be popular among Divines and Moraliſts, and has been mangled and metamorphoſed even by our philoſophers themſelves) was adopted by the Greeks, was infuſed into the ſubtile and intricate philoſophy of Ariſtotle, dilated upon by the divine genius of Plato, beautified by the ſublime inven⯑tion of that moſt ancient of their poets and philoſophers, the immortal Homer; and, at length, was taught by Plutarch to the Roman World, in the following manner:

‘"Man,"’ ſays he, ‘"is a compound ſubject, but not of two parts, as is commonly believed, becauſe the underſtanding is generally accounted a part of the ſoul; whereas it as far exceeds the ſoul, as the ſoul is diviner than the body. Now the ſoul, when compounded with the underſtanding, makes REASON, and, when compounded with the body, makes PASSION; whereof one is the ſource or principle of [11]pleaſure or pain—the other of vice or virtue. Man, therefore, properly dies two deaths; the firſt makes him two of three, and the ſecond makes him one of two."’

This hypotheſis has certainly beauty and ingenuity to re⯑commend it to our imaginations; and is alſo, to my concep⯑tions at leaſt, ſomewhat more comprehenſible than thoſe ſyſ⯑tems which refer the operations of groſs matter to immaterial agency. It is, however, like all the ſpeculations of the an⯑cients upon theſe ſubjects, unfounded in experimental en⯑quiry, and unſupported by facts or obſervation: yet St. Paul, (who derived much of his inſpiration from the ancient poets and philoſophers) has given it the ſanction of his authority, by dividing, in diſtinct terms, the triune man into Body, Soul, and Spirit.

This being the caſe, it is not at all ſurpriſing that modern philoſophy ſhould have been more anxious to frame ſuch ſyſ⯑tems as were reconcileable with this tripartite diviſion, than ſuch as might be conſiſtent with known facts, or maintain⯑able on the grounds of reaſon; and that we ſhould accord⯑ingly find this theory ſo ſtoutly defended to the preſent hour, with the ſlight alteration only of tranſpoſing the ſoul into the place of mind or ſpirit, and ſubſtituting Vital Principle in the place of ſoul. Some philoſophers, however, by conſidering [12]the immaterial eſſence as the animating principle, and others, by conſidering the animating principle as the only medium of intelligence, have reduced human exiſtence to a two-fold nature: I, for my part, ſhall ſimplify the ſubject ſtill far⯑ther—and, regarding man as differing from other animals rather in the extent than in the nature of his powers, ſhall conſider him, together with the inferior tenants of creation, in an individual point of view only; as conſiſting of a ſim⯑ple organized frame, from the ſuſceptibility and preſence, or the non-ſuſceptibility, or abſence of ſtimuli in which ariſes the whole diſtinction between the living body and the dead. Wherever there is a perfect organization of the animal ſub⯑ſtance, there, I conceive, we have the ſuſceptibility (or, as it may, perhaps not improperly, be called, the PRE-DISPOSING CAUSE) of Life: whatever may be that ſpecific ſtimulus, by which ſuch ſuſceptibility may be diſpoſed to be excited, that, I conceive, muſt be admitted to be the REMOTE CAUSE, or agent by which Life is to be produced: from the intimate combination of theſe reſults, that meliorated or altered ſtate of the organized frame, which may be conſidered as the PROXIMATE CAUSE; and the Vital Action, as it may pro⯑perly be called, or the power by which the vital functions are performed, being the ultimate effect of theſe co-operat⯑ing cauſes, is, in reality, as I humbly preſume, to be conſi⯑dered as that Life, or Animal Vitality, for which, under ſo [13]many denominations and imaginary forms, the Philoſopher and the Medical Profeſſor have ſo long been ſeeking.

Such is the general idea, which, upon the ſimple princi⯑ples of materialiſm, I have formed of life; and ſo to define this idea as to account for the phenomena, without appealing to the fanciful creations of the viſionary brain, or abſtruſe and unmeaning terms of pretended ſcience, is the taſk I have undertaken.

But before I enter more particularly into the ſubject, it will be neceſſary to beſtow ſome conſideration on another theory that has lately very much amuſed, and, according to my judgment, miſled the ſcientific world—The theory, I mean, of the Vital Principle being reſident in the blood.

This doctrine, in all probability, had its origin in the re⯑moteſt antiquity; ſince the fatal conſequences that reſult to the animal frame, from the ſpilling of this important fluid, muſt have been frequently obſerved, eſpecially in the ages of bar⯑bariſm and violence, long before the faculties of man were ſufficiently improved for refined ſpeculations, or philoſophi⯑cal reſearches into nature: but the prejudices of ignorance have ſometimes been aſcertained, and more frequently adopted, by the luminaries of ſcience and the world; and this haſty opi⯑nion [14](for ſuch to me at leaſt it appears) has not wanted ſup⯑porters among thoſe who will long continue to claim the ap⯑plauſe and admiration of mankind.

And firſt, I muſt particularize, that this doctrine has re⯑ceived the direct ſanction of the great Jewiſh Law-giver (or whoever was the author of the Five Books of Sacred Hiſtory generally aſcribed to him) in the following, among a variety of texts of a ſimilar nature—‘"For it is the life of all fleſh; the blood of it is the life thereof: therefore I ſaid unto the children of Iſrael, Ye ſhall eat of the blood of no manner of fleſh: for the life of all fleſh is the blood thereof; whoſoever eateth it ſhall be cut off."’

I am very well aware, that the ſublime language of Reve⯑lation is not always to be interpreted with philoſophical pre⯑ciſion—the enthuſiaſm of divine inſpiration frequently elevat⯑ing the ſtyle of the holy penman to a degree of poetical hyperbole, which would be perfectly unintelligible to the cold perceptions of reaſon and enquiry, if it were not for the friendly appeals of the commentator to myſtical allegory, and metaphorical elucidation: but as the doctrine here quoted is merely illuſtrative of the ſimple mandate, that the Jews ſhould not eat of the blood of animals ſlain for their ſuſtenance, there can be no doubt of its being intended to be literally [15]underſtood as the opinion of Moſes, that the blood is abſo⯑lutely the Vital Principle.

For this opinion, I am very much inclined to ſuſpect, that no better foundation will be diſcovered than the acknow⯑ledged fact, that when the blood, or any very conſiderable portion of it, is drawn away, the vital functions of the ani⯑mal will ceaſe: but, unfortunately for this theory, theſe functions will alſo ceaſe, without the proportion of this fluid being at all diminiſhed: and as there are alſo ſeveral other parts entering into the compoſition of the animal, which, if ſubtracted, even in part, reſign the body to inevitable de⯑ſtruction, we might as well ſay, that the ſtomach thereof, or the kidneys, or the liver thereof, is the life thereof, as that the blood is to be ſo conſidered. Nay, from what we are now ac⯑quainted with concerning the nervous ſyſtem, there would be much better reaſon to ſuppoſe, with ſome later philoſophers, that the life of the animal is in the brain, rather than in the blood, ſince ſo much of the latter may be loſt without eſſential injury, while the former cannot receive the ſlighteſt wound without bringing on immediate diſſolution; and though, upon ſerious reflection, there is every reaſon to believe, that the fatal cataſtrophe is produced as much, at leaſt, by the conſequent extravaſation of the blood, as by any imme⯑diate ſuſceptibility of injury in the ſubſtance of the brain; [16]yet this does not weaken the argument, ſince it is evident, that it is not the loſs of blood from the veſſels which is the real cauſe of the miſchief (for much larger quantities may be drawn from the ſame part by mere external wounds, without any alarming conſequences); but that the injury produced by the extravaſation reſults from the conſequent oppreſſion on the organ, by which its active energy is re⯑ſtrained and benumbed, and, of courſe, its vital functions will be ſtopped.

From this, and a variety of other conſiderations, it is evi⯑dent that the brain is, at leaſt, more vital than the blood, ſince the compreſſion of the former is more dangerous than even a very conſiderable deduction of the latter.

But it might, perhaps, be objected to the whole of this reaſoning, that many animals have life, which have neither brain, nor kidneys, nor liver, nor, ſtrictly ſpeaking, even ſto⯑machs; for I know not how the ſimple cavities of the leech or polipus can, in ſtrict propriety, be conſidered as ſto⯑machs.

This objection being founded in truth, it is neceſſary that we ſhould give it its utmoſt force, and admit it as a demon⯑ſtration, that animal life neither conſiſts in, nor is abſolutely [17]dependant upon any one of theſe particular organs: but as it will be admitted, that though they have not theſe, they have ſome other organs, which, as far as is neceſſary for the performance of their functions, ſupply the place of theſe, the caſes will ſtill be found to be in ſome degree parallel—for, ſtrictly ſpeaking, many of the moſt imperfect animals have no blood (at leaſt, according to the general idea which is given of it in the deſcriptions of anatomiſts), there being, perhaps, as much difference between the ichor, which ſupplies its place in ſeveral claſſes of inſects and reptiles, and the com⯑pound fluid, which, in the more perfect animals, we call by the name of blood, as between this ichor and the ſap of vege⯑tables, and a variety of other ſimple juices of animal or ve⯑getable ſubſtances. If, therefore, the Vital Principle is to be ſought in the circulating fluids, we ought rather to ſay, that the SERUM thereof is the life thereof, than the BLOOD.

But as I am informed, that the immortal Harvey upheld a doctrine ſimilar to that I am combating; and as ſo great an authority as John Hunter has thought proper, in ſome de⯑gree, to ſanction the opinion, it is neceſſary to treat it more at large, and to abandon the curſory obſervation of the Jewiſh Law-giver, for the more elaborate and practical reſearches of the Britiſh Anatomical Philoſopher.

I have ſaid, that John Hunter's Theory ſanctions, in ſome degree, the opinion of Moſes; for I think it very doubtful, whether he means to carry it to the full extent, and to aſſert, that the Vital Principle is peculiarly, or originally, in the blood. The Editors of the Encyc. Brit. it is true, (title BLOOD, vol. iii. p. 313), evidently underſtood him in this manner, as will appear from the following quotation: ‘"The uſes of this fluid are ſo various, and of ſuch an important nature, that ſome have not ſcrupled to affirm the blood to be actually poſſeſſed of a living principle, and that the LIFE of the whole body is derived from IT. This opinion was firſt broached by the celebrated Harvey,"’ (this I have already ſhewn to be a miſtake ^*), ‘"the diſcoverer of the circu⯑lation: but in this he was never much followed; and the hypotheſis itſelf, indeed, has been pretty much laid aſide and neglected, till of late that it was revived by Mr. J. Hunter."’ After which are quoted the ſix arguments, (which I ſhall preſently endeavour to examine) as advanced by that great profeſſor, to ſupport this broad and unqualified opinion: but, in the manuſcript copy of his Lectures, which I have principally made uſe of, he begins the ſubject with the ſimple aſſertion only, that the blood ‘"is en⯑dowed with a principle of life, in itſelf, equally with the ſolid parts."’

Now, whether all or any, either of the particular fluid or ſolid parts,^* poſſeſs in themſelves (that is to ſay, either ſe⯑parately, or abſolutely) a principle of life, I do not at preſent enquire, becauſe it ſeems to involve the general queſtion, (which muſt be referred to its proper place in my Eſſay); namely—Whether life itſelf is to be conſidered as a diſtinct and poſitive eſſence, or, ſimply, as the reſult of a particular harmony and correſpondence of the whole, or aggregate combination, preſerved and acted upon by a particular ſtimulus? On this ſubject, indeed, it is ſufficiently evident that I have the misfortune to differ from the illuſtrious authority before me; but as I am now examining the doc⯑trine only of the Vitality of the Blood, it is but neceſſary for me juſt to obſerve, that as nothing more is directly aſſerted in the propoſition, than that the blood of the living body is equally alive with the bones and ligaments, and muſcular fibres, &c. of which ſuch living body is compoſed, it does not ſeem to lie conſiderably in the way of my theory; be⯑cauſe, if in other reſpects I can but ſubſtantiate my opinion, the difference will not be very great, whether we admit the blood as participating in the Vitality, produced as I ſhall en⯑deavour [20]to ſhew, or conſider it as nothing more than a ſpe⯑cific fluid, giving nouriſhment to the various ſubſtances, and conveying to the different organized parts the neceſſary ſti⯑muli, by which Life or the Vital Action is to be produced or ſuſtained. Nay, when he afterwards proceeds to aſſert, that ‘"Blood is not only alive itſelf, but alſo, by circula⯑tion through every part of the body, becomes the means of, and carries Life to, the other parts;"’ I do not yet perceive the abſolute neceſſity of entering the liſts upon this part of the ſubject, becauſe he does not palpably aſſert, that the Life to be conveyed is, ſui generis, or originally in the blood; but only that this fluid is the agent by which the Vitality is communicated to the reſpective parts; and it is my intention to admit that the blood, in the more perfect, and the ſerous fluid, ſubſtituted in its place, in the leſs perfect animals, is the appropriate medium, by which alone the ſtimuli neceſſary for the production and ſuſtainment of Life can be abſorbed and properly diffuſed through the organized frame: and, indeed, ſeveral paſſages might be produced to countenance the ſuſpicion, that this juſtly admired Lecturer ſo far agrees with the Theory I mean to enforce, as to admit that the Vital Principle is, at leaſt, ſuſtained and re-invigorated (if not abſolutely generated), not independently by the blood itſelf, but from ſomething imbibed in its paſſage through the lungs; for he acknowledges, that ‘"Before blood is capable of giving [21]life,"’ (in other words, according to his own theory, before it is alive), ‘"it muſt have circulated through the lungs, where it undergoes ſome eſſential change. Perhaps,"’ continues he, ‘"it is then in its ſecond ſtate, or vivification."’

It is obvious to remark, that if the blood is not ‘"in its ſtate of vivification"’ till it has paſſed through the lungs, Vitality cannot be the property of the blood itſelf, but only a conſequence of ſome action, or ſuperaddition, acquired in its paſſage through that organ; and, conſequently, that the Vital Principle (to uſe the language of thoſe philoſophers who conſider Life as a ſeparate eſſence) is to be ſought, not in the blood, but in that ſubtile element, or whatever it is, which is imbibed by means of the reſpitory ſyſtem.

But (if it is not preſumption for me to ſay ſo) there ſeems to be ſome degree of obſcurity—perhaps, if I were ſpeaking of any man but John Hunter, I ſhould venture to ſay contradiction, in the doctrines of the Lecturer, upon this ſub⯑ject; for he immediately afterwards denies that the blood derives its Vitality from its paſſage through the lungs, in the following words: ‘"Perhaps it might be thought that Life is given to the Blood in the Lungs in conſequence of the heat applied there, as heat is ſuppoſed to act upon the Egg; but it muſt be remembered, that Life is not given to [22] the Egg by heat, only action produced by it."’ By which it ſhould ſeem that he means to be underſtood as conſidering the Vital Principle to be a property of the blood itſelf (ſo long as it continues in its perfect ſtate) independent of reſpiration; and that this action of the Lungs is only neceſſary for the purpoſes of circulation, and the production of action in the other parts of the frame, by the diſtribution of this principle.

And yet, if the Egg be alive (which, let it be remember⯑ed, I do not poſitively admit), how can this be? ſince (pre⯑vious to the alteration taking place, from the application of heat, during the period of incubation), it contains no blood whatever; and, conſequently, if the Vital Principle be in the blood, muſt be alive without the principle of life—a paradox, which, perhaps, it would be a little entertaining to hear the advocates of this doctrine explain.

Not, however, to dwell upon ſo ambiguous a paſſage, there are, in the Lectures of this truly great man, ſufficient foundations for the opinion apparently entertained by the Editors of the work above quoted, as well as by ſeveral of his pupils and admirers—namely, That he means to repreſent Vitality, or, according to his own expreſſion, the Vital Prin⯑ciple, as reſiding originally, and in an emphatic ſenſe, in the [23] blood, and derived from it to the other parts of the ſyſtem. He even, in the cleareſt manner, affirms its ſuperior vivifica⯑tion over the nerves in particular: for while theſe, accord⯑ing to one of his aphoriſms on the Vitality of the Blood, are not concerned in ‘"conveying life to parts, but only direct the motions of the parts,"’ the blood is explicitly affirmed not only to ‘"convey life to the other parts,"’ but to be ab⯑ſolutely ‘"the living ſupport of the nerves themſelves:"’ by which it is evident, that we muſt underſtand not only that the nouriſhment of theſe ſenſitive organs, but even their Vitality, is derived, not from their organization and the ſtimuli (of which they are, perhaps, the important repoſitories, or reſer⯑voirs), but from the Vital Principle peculiarly reſident in the blood, and depoſited there for the purpoſe of being commu⯑nicated and diffuſed to other parts.

Theſe other parts then being dependant (according to this theory) upon the blood, not only for their ſupport and en⯑largement, but, alſo, in an immediate view, for their Vitali⯑ty, it is clear that if the ſyſtem of the Lecturer does not go the whole length with Moſes, of ſaying that the blood of the animal is the life thereof, at leaſt that he ſuppoſes Life, of itſelf, and independent of any particular action or ſtimu⯑lus to belong to, or be a property of, the blood; while to the reſt of the animal ſubſtance, it only belongs in a ſecondary [24]ſignification, as being imparted by the blood. And this, per⯑haps, we are the more bound to conſider as his real meaning, as he maintains the doctrine of its vitality even after coa⯑gulation; and even delivers it as his opinion that this phe⯑nomenon ‘"is owing to an action of ſelf-preſervation in the blood, or to an effort for its continuance."’ So that, ac⯑cording to this poſition, and the arguments that follow upon the circumſtance of coagula becoming vaſcular under parti⯑cular circumſtances, we are not to conſider the vitality of the blood as the conſequence of its ſtate, condition, and har⯑mony, with the other parts ^* of the body, but to look upon it as a principle inherent in it, and equally a property of it, whether in one ſtate and ſituation, or another—whether in its veſſels, or in a ſtate of extravaſation—whether in a fluid or a ſolid form—a circumſtance attributed to no other of the component parts of the animal frame: theſe being con⯑ſidered as having no other principle of life, but what they immediately derive either from the blood, or from their harmony with the ſyſtem in general; whoſe reſources muſt ceaſe before any material change in their nature and ſubſtance can take place. And yet, if this argument is properly ſifted, I queſtion whether it will make much for the Vitality of the blood, in any point of view whatever. For as no ſimilar change in any other fluid was ever brought forward as an evidence of a Vital Principle in ſuch fluid, I cannot [25]ſee that any phenomenon, that would not be conſidered as a proof of Vitality, or of an effort of ſelf-preſervation, in any other inſtance, ſhould have ſuch ſtreſs laid upon it, for ſuch purpoſes in the caſe before us.

With reſpect to the generality, probably to all, of the fluids capable of congelation, it might, perhaps, be objected, that they afford no parallel example of permanent change of ſtructure; as they are capable of reſolution to their original form, which blood is not. But petrified ſubſtances, in which the change is permanent and entire, might at leaſt be ſaid, in this reſpect, to have as good a claim to the attributes of a vital principle and action of ſelf-preſervation, as the blood, which is here ſaid to metamorphoſe itſelf into ſomething elſe, in order to continue its exiſtence. Beſides, if the coagulation of the blood be an action of its Vitality, and an effort of its Vital Principle for its preſervation, how comes it that it will coagulate after having been frozen; for John Hunter admits, that what he calls the Vital Principle of the Egg, is deſtroyed by freezing; and, indeed, nothing is more injurious to vitality of every kind, than the frigorific proceſs: and yet Mr. Hewſon informs us, that blood may be completely frozen, and pre⯑ſerved in that condition (as other dead animal ſubſtances may) for a conſiderable time; and yet, after it is again re⯑duced, by an increaſe of temperature, to its fluid form, it will coagulate juſt as uſual.

Having thus examined the general ſtate of the queſtion, I ſhall preceed to review the ſix arguments brought forward upon the authority of the lecturer, in the Encyclopedia, in ſupport of the opinion previouſly quoted—(vide page 18 of this Eſſay.) For the more ample ſtatement of theſe, how⯑ever, (not to ſwell my Eſſay to an unneceſſary length, by quotations from a book, which is in the hands of every body) I ſhall refer to the work itſelf.

With reſpect to the firſt of theſe, derived from ‘"the power which the blood poſſeſſes, of uniting living parts,"’ it is to be remembered, that this is only the caſe in thoſe in⯑ſtances where blood is immediately ſupplied by the parts to be united, and where, conſequently, from its temperature, its aſſimilitude to the parts with which it is to enter into com⯑bination, its glutinous texture, and a variety of obvious reaſons, it may naturally be ſuppoſed to form the beſt cement⯑ing medium; and the healing of wounds, by other applica⯑tions, which have evidently no Vital Principle, appears to me ſufficient to ſhew, that this is no proof of Vitality. All that is requiſite, in either inſtance, being to keep the living parts in contact, and exclude the air, and other injurious, extra⯑neous particles, till Nature has a ſufficient opportunity of ex⯑erting her reſtoring powers.

The blood, yet warm, and fluid from the wound, may na⯑turally enough be expected to enter intimately into the dif⯑ferent portions of the ſevered parts; and all further injuries being thus prevented, it is neither ſingular nor ſtrange, that the ſeparated veſſels ſhould again unite, from the attraction of ſimilar particles ſo frequently obſerved, when circum⯑ſtances are favourable to the experiment; and that the ſtream of blood, driving towards its uſual courſe, ſhould at laſt find its way again through the coagulum formed by the blood thus bound up with the injured parts, and complete their reſto⯑ration.—2 and 6. Exactly upon the ſame principle I account for the phenomenon from which the ſecond argument is drawn; namely—That ‘"coagula of extravaſated blood will become vaſcular:"’ for this, I believe, is never the caſe, except when the coagula come in contact, or nearly in contact, with arteries previouſly formed. This, therefore, ſeems to prove nothing more than that coagulated blood, when preſerving a proper degree of temperature, from its ſituation, is the proper medium, or ſoil, into which the arteries may ſtrike and ramify—all living parts, perhaps, having a tendency to grow and enlarge, ſo long as ſufficient ſtimuli are ſupplied, and the proper medium is preſented. For my own part, I cannot but obſerve, that all the preparations I have ſeen, intended to ſup⯑port this argument, have only ſuggeſted a proceſs ſimilar to that obſervable in vegetation, where the moiſt earth, in contact [28]with the roots of plants or trees, ſupplies the proper medium into which the fibres are ſtimulated to extend their growth. And hence it is, that I find no difficulty in accounting for the junction of the teſticle of the cock, to the liver of the hen, into whoſe abdomen it had been introduced, as mentioned in illuſtration of the firſt argument; or, for the vaſcular appear⯑ance of the coagulum, found between the ſeparated parts of the fractured os humeri, upon which the ſixth, or rather the reiteration of the ſecond argument, is founded.—3. As for the third argument, drawn from the power of the blood, to pre⯑ſerve an equal degree of temperature in the living body, dur⯑ing the prevalence of different temperatures of the atmoſ⯑phere—I ſhall at preſent make no other anſwer to this, than by obſerving, that if the Theory I am about to ſuggeſt is well founded, that will be ſufficient to account for this pheno⯑menon, without appeal to any other hypotheſis: for if the air may be admitted to be ſufficiently impregnated with the ſame ſpecific ſtimuli in the coldeſt, as well as in the hotteſt day, there can be no reaſon why the blood ſhould be expect⯑ed to have a lower degree of temperature on the former than on the latter—whether it be admitted to be poſſeſſed of a Vital Principle independent of ſuch ſtimuli, or not.—4. As for the ‘"Blood being capable of being acted upon by a ſtimulus,"’—this is ſaying no more than may be proved of a variety of things that have confeſſedly no pretenſions to life [29]whatever: and as the only particular effect which is inſtanced as produced by the ſtimulating influence on the blood, (namely coagulation), would never be admitted as a proof of life in any other fluid whatever, it cannot, as far as I am able to diſcover, be made any uſe of in illuſtration of the point in queſtion. 5. The fifth argument, that ‘"the blood pre⯑ſerves life in different parts of the body,"’ is equally applica⯑cable to the Theory of the Lecturer, and to my own; for, whether it be conſidered as retaining in itſelf the Vital Prin⯑ciple, or being the ſole medium through which Vitality can be produced, we muſt equally admit its importance, not only in preſerving, but in diffuſing life: I ſhall therefore only obſerve, that the collateral part of the argument, which aſſerts, that ‘"when the nerves, going to a part, are tied, the part becomes paralytic,"’ is, I believe, overthrown by later experiments; and that ſenſation only, and not the power of acting the muſcles, is interrupted by the ligature of nerves. Upon this, however, (as I certainly do not mean to rob the blood of its vital honours, to beſtow them on the Brain and Nerves), I ſhall not at preſent enlarge; but ſhall conclude what I have to ſay upon this ſubject, by obſerving that, per⯑haps, the whole doctrine of the Vitality of the Blood (in whatever point of view it may be taken) originated in the mind of the Lecturer, from obſerving the important offices it performs in the fuſtainment and reproduction of parts con⯑feſſedly [30]and palpably alive. Now, that the nerves (for ex⯑ample), as well as every other part of the animal body, are nouriſhed by the blood, is ſufficiently evident, and that, but for ſuch nouriſhment, theſe parts muſt, by exhauſtion, loſe their Vitality, is equally obvious; but that the fluid, nou⯑riſhing and ſuſtaining a living part, muſt of neceſſity be itſelf alive, is what I cannot readily admit, becauſe it ſeems to con⯑tradict the known laws and phenomena of nature. Air and water are the proper and neceſſary nouriſhment of plants, without which vegetation muſt quickly be exhauſted and ex⯑pire; but no one will, therefore, contend, that air and water are alive: nor will the difficulty be removed, by objecting, that air and water are only the food of plants, and that the nouriſhment of the vegetable is immediately derived from the circulating ſap, as that of the animal from the blood; for as no digeſtive proceſs can be aſſigned to the plant, air and water muſt be the immediate nouriſhers of the ſap; and, con⯑ſequently, the concluſion muſt either be, that the living ſap is nouriſhed by air and water, which are not alive, or that the ſap, which is not alive, nouriſhes the living plant; which, with reſpect to the argument before us, is juſt the ſame: in ſhort, it might as well be maintained, that whatever ſupports a ſenſi⯑tive part muſt itſelf be ſenſitive; or that nothing but nerve ſhould nouriſh a nerve, or muſcle but muſcle, &c. which would drive us back to the obſolete opinion of thoſe philoſo⯑phers, [31]who maintained, that all things contain the compo⯑nent parts of all things; and, in ſhort, would even compel us to appeal to the doctrine of an ancient ſect of Atheiſts, who, to get rid of the neceſſity of a Deity, inſiſted upon the original and eternal Vitality of matter, and accounted for the growth and nouriſhment of living things, by arguing, that the particles that nouriſhed them were themſelves poſ⯑ſeſſed of a living principle. If, however, we abide by the mode of reaſoning ſuggeſted by the known phenomena of nature, a much more ſimple theory will preſent itſelf, in the evident tendency of ſmall accumulations of matter (when placed under favourable circumſtances) to aſſimilate, and even identify themſelves with the larger maſſes to which they adhere, or with which they enter into combination; which will ſufficiently account for the nouriſhment and growth of the living body, without attributing Vitality to the blood, by which it is ſuſtained.

Having thus taken as brief a ſurvey as the nature of the ſubject would permit, of ſome of the principal opinions, that have, at different times, commanded the attention of the ſcien⯑tific world, I ſhall proceed to the profeſſed object of my Eſſay; namely—to conſider of the Definition. Of this un⯑dertaking the difficulty muſt be readily admitted; or, ſhould pride or petulance be inclined to deny it, the ſubterfuges to [32]which the moſt ingenious ornaments of medical ſcience have been driven, would furniſh a ſufficient reply. Some have given it up entirely, and ſatisfied themſelves with a nega⯑tive teſt, inſtead of a poſitive definition; aſſerting, that the only criterion of its abſence is putrefaction: but theſe cautious maxims, though they may be adopted, for ſecurity, by the practitioner employed in the benevolent labour of ſnatching from premature diſſolution the pale victims of accident or deſpair, will not ſatisfy the ſpirit of the philoſophical en⯑quirer: he, indeed, may frequently be compelled to wander in the gloom of doubt and negation; but his active mind will ſcorn ſuch ſullen darkneſs, and pant for the glorious proſpects of truth and certitude; to which, however, I have not the arrogance to profeſs that I ſhall conduct him.

By ſome it has been contended, that life conſiſts in action, or excited irritability; by others, ſimply in organization: but both of theſe would admit a variety of inſtances, that can lay no claim to any ſort of Vitality, much leſs to that ſort of Vitality which is the ſubject of the preſent paper: with reſpect to the former, I need only inſtance, that parch⯑men, leather, thread, &c. may be excited to conſiderable action by either heat or moiſture, as may alſo a variety of light bodies, by the application of electricity: and, as for orga⯑nization, this I conſider to be no other than that arrangement [33]of diſſimilar parts, by which a harmony and communication of the whole is produced, ſo as to enable it to preſerve itſelf in a given ſtate, and reſiſt its own diſſolution. This, therefore, is very inadequate to our idea of life; for matter will continue to be organized when LIFE has ceaſed; as it alſo, I conceive, muſt be organized before LIFE begins; in illuſtration of which, I ſhould rather be inclined to quote the inſtance of the Egg, which (with all the deference due to the high authority of John Hunter) appears to me to be organized, though not alive, previous to incubation: I conceive alſo, that many bodies may be conſidered as organized, that were never intended to live at all. To thoſe, however, who wiſh to conſider life as en⯑tirely dependant on Organization, I ſubmit the following Definition: That perfect harmony of organized parts, by which the animal frame is rendered ſo far ſuſceptible of the proper ſtimuli, as to have its functions, or any of them, induced upon ſuch ſtimuli being applied: and this the Society will be kind enough to keep in their minds, as what I mean, when I come hereafter to ſpeak of Specific Organization.— Others have conſidered Animal Life as conſiſting in the performance of the Animal functions: but this definition would exclude, from all pretenſions to Vitality, many beings, which common ſenſe muſt admit to be alive; for an animal may certainly live, when it neither does, nor can perform, all its functions; and, as for aſcertaining which may be diſ⯑penſed [34]with, and which may not, this, I believe, has never been ſucceſsfully attempted.

The definition of John Hunter appears to me particu⯑larly vague and unſatisfactory. ‘"Life,"’ ſays he, ‘"does not conſiſt in any modification of matter: it either is ſomething ſu⯑peradded to matter, or elſe it conſiſts in a peculiar arrange⯑ment of certain fine particles of matter, which, being thus diſpoſed, acquire the properties of Life."’ The Diſciples of this juſtly celebrated man muſt pardon me, if I am inclined to ſmile at this definition, or rather indefinite deſcription of Life, and to declare, that I never in my life met with any thing more completely incomprehenſible. ‘"Life does not conſiſt in any modification of matter;"’ and yet, perhaps, ‘"it conſiſts in a peculiar arrangement of certain fine particles of matter, which, being thus diſpoſed, acquire the properties of Life!"’ What is the fineneſs of theſe particles of matter, but a modification of matter?—What is the peculiar arrangement— what the diſpoſition of theſe particles, but a modification of matter? In ſhort, is not this telling us, in other words, that Life poſitively is not a modification of matter, but that yet, per⯑haps, it is a modification of matter? As for the other poſition, that Life conſiſts in ſomething ſuperadded to matter, I had once occaſion to controvert this incomprehenſible axiom at the Lyceum, when, all of a ſudden, a ſneer went [35]round the Theatre, and a hundred mouths were filled with fury againſt me, as though I had ſtood up, in the preſence of the Pope and his Cardinals, to deny the doctrine of the Tri⯑nity. I ſhall venture, however, once more to aſſert, that the ſpiritual alluſions of this ſentence are too fine for the groſs conceptions of my material organs. According to my dull comprehenſions, matter and vacuum ſtand preciſely in the ſame degrees of contradiſtinction as ſomething and nothing; and, in the former caſe, as in the latter, it is impoſſible for me to admit the negation of the one, without, at the ſame time, acknow⯑ledging the affirmation of the other.—Where there is not matter, there there is vacuum;—where vacuum is not, there there muſt be matter. Thoſe effects, which are not produced by the operations of ſome modification of matter, or, in other words, of ſomething, muſt of courſe be produced by ſome modification of vacuum, or, in other words, of nothing; and how vacuum, or nothing, can be ſo modified as to produce Life, I leave to the conſideration of the Metaphyſicians. It is evident, however, that this is not what the Lecturer means; becauſe, though he denies the modification of matter, he admits the ſuperaddition of ſomething.—But what is this ſomething that is not matter?—Is it Spirit? I certainly do not think it the part of a philoſopher abſolutely to deny the exiſtence of every thing that he cannot demonſtrate; but, as contradic⯑tions are not to be admitted, I muſt, for my own part, main⯑tain, that if there is any ſuch thing entering into the animal [36]compoſition (though our ſenſes have never yet been capable of taking cognizance of it) as Spirit, having an exiſtence ſe⯑parate and diſtinct from organization, and that groſs periſh⯑able kind of ſubſtance we call body, that ſuch Spirit, how⯑ever ſubtile, however refined, muſt ſtill be material: and then, indeed, the abſurdity vaniſhes—becauſe that more ſub⯑tile matter can act upon that which is more groſs and inert, we have ſufficient evidence in the action of air, and of the electric fluid. And that this (a fine and ſubtile, or aeriform eſſence) is the real and genuine meaning of the term Spirit, about which divines and philoſophers have ſo long been con⯑tending, is, I conceive, ſufficiently demonſtrable, not only from its etymology, but alſo from the common application of the word in the other ſenſes in which it is ſtill retained: as, for example,—by the ſpirit of any diſtilled or fermented fluid, we always mean to expreſs that more ſubtile and vola⯑tile principle (the alkohol of the chemiſts) mixed with, and dif⯑fuſed through ſuch fluid, and whoſe materiality (notwith⯑ſtanding its ſuperior ſubtility) is no more to be queſtioned than that of the groſſer parts of the fluid with which it en⯑ters into combination. In ſhort, it will perhaps be found, that all Nouns, immediately or arbitrarily derived from Verbs,^* whether of the ſame, or any other language, ſtill re⯑tain, [37]in a conſiderable degree, their paternal ſignification; and ſpirit muſt, perhaps, be admitted to bear no other mean⯑ing than the Latin ſpiro (to breathe), from which it is con⯑feſſedly taken: or, if we muſt needs make a diſtinct living exiſtence of it, then can it poſſibly mean no other than a vital aëriform ſubſtance, diffuſed though the frame, and giv⯑ing animation to the reſpective parts. So that, at any rate, this ſomething ſuperadded to matter, can only be a more re⯑fined ſpecies of matter added to that which is more groſs; and, of courſe, it conſtitutes that very modification which the Lecturer denies.—It has been ſtated, in defence of this paſſage, that by ſome thing ſuperadded, no more is meant than ſome quality; but this would by no means mend the matter, ſince nothing can be added but what has a previous and ſeparate exiſtence. Two things brought together may, it is true, occaſion the exiſtence of a third, different from both; but this third is not added, but produced. Now qualities have no ſeparate exiſtence, nor can they even be conceived in the imagination, otherwiſe than as connected with the things of which they deſcribe the ſhades or attri⯑butes: they are, in fact, ſolely and purely, modifications of matter, and, conſequently, this interpretation involves all the abſurdity and contradiction of which I have before com⯑plained.

But it is much more eaſy to find fault with the definitions of others, than to frame ſuch as are not faulty: I ſhall pro⯑ceed, [38]therefore, to my taſk with caution; and, beginning with a general, proceed to a particular definition.—Life then, in the animal, we will ſay, is that ſtate of action, by which the functions, or any of the functions of the animal, are carried on. This definition, it is true, neither points out how the action is ſuppoſed to be induced, nor the ſtate of the animal previous to the induction: I proceed, therefore, to add, that, previous to the exiſtence of life, the body muſt have attained a SPECIFIC ORGANIZATION; and that Life, or, in other terms, the Vital Action, is induced by the application of proper ſtimuli: thus, then, life in the animal is that ſtate of action (induced by ſpecific ſti⯑muli upon matter ſpecifically organized), by which the animal functions, or any of them, are carried on. To the whole of this, I know, may be objected, the aſſertion of that great man, whom, with ſuch repeated arrogance, I have ventured to op⯑poſe: namely—That Life may exiſt without matter, being in ‘"a ſtate of action, and the property of ſelf-preſervation may alone be preſent, Life being at the ſame time preſent in its full force."’ To the ſolitary inſtance, however, brought in ſupport of this aſſertion, I muſt reply, that the life of the Egg is by no means obvious to my underſtanding; for, although the Egg be ſo far organized as to be endowed with the principle of ſelf-preſervation; ſo, alſo, are various fruits, &c. whoſe Vitality, I ſuppoſe, after they are plucked, will not be contended for^*. In ſhort, it does not appear to have any one [39]property or attribute, which, in any other ſubſtance, would be deemed a ſufficient teſt of Vitality, till the ſtimulus of heat, being properly applied, ſo meliorates the arrangement of par⯑ticles, as to induce the ſpecific organization eſſential to the ſuſceptibility and production of Vital Action.— By this, then, it will appear, that I conſider the prelimi⯑nary principles of life to be a ſpecific organization and a ſpecific ſtimulus; the perfect contact of theſe to be the immediate cauſe, and life itſelf to be the ſtate of action produced by this union.

It will now only be expected, that I ſhould give an opi⯑nion upon the nature of the ſtimulus required. But, in order to do this, I muſt firſt premiſe, that I conſider the Blood, in⯑dependent of its nutritive power, as the ſpecific medium by which the ſtimuli muſt be conveyed to the different parts of the organized frame, ſo as to produce the Vital Action. This Blood, then, in its paſſage through the Lungs, collects a ſomething, which generates a ſpecific heat (for it is evident, that heat, unleſs thus generated, will not anſwer the purpoſe), which it diffuſes through the whole vaſcular ſyſtem, and then (exhauſted of its vivifying power) returns again to the lungs, to exhale whatever noxious particles it may have collected, and to inhale a freſh portion of the ſame vivifying principle. But what is this ſomething—this vivifying principle?—Is it atmoſpheric air itſelf?—Certainly not. The coats of the ar⯑teries, and the membranous linings of the cells of the lungs, forbid the acceſs of ſuch an element; beſides, it has been [41]proved by experiment, that in the arteries of the living body there is no air. Something, however, it muſt be, that is con⯑tained in the atmoſphere, and ſomething of a powerful and exquiſitely ſubtile nature.

If, then, we look upon the component parts of our atmoſ⯑phere, what can we diſcover ſo competent to the taſk—ſo ſubtile, ſo powerful, ſo nearly approaching to that idea of an ethereal medium, which ſome philoſophers have ſuppoſed ne⯑ceſſary to complete the chain of connection between the di⯑vine immortal eſſence, and the dull inertion of created mat⯑ter, as the electrical fluid?—that principle, whoſe preſence, under ſuch a variety of forms, is conſtantly preſenting itſelf to the reſearches of the philoſopher!—whoſe agency, in ſo many of the phenomena of Nature, we are daily detecting! and which, perhaps, will one time be diſcovered to be the real principle by which all heat and action are originally generated and maintained!