Far from all vision this profoundly lurks, But it is to the astonishing discoveries of modern chemistry alone that we are indebted for any fair application of any such fluid to account for the phænomena of life. Amongst the numerous gases which modern chemistry has detected, there are three which are pre-eminently entitled to our attention, though they seem to have been glanced at by the Epicureans: caloric, or the matter of heat, chiefly characterised in our own day as a distinct substance, by the labours of Dr. Black and Dr. Crawford; oxygene, or the vital part of atmospheric air, first discovered by Priestley, and explained by Lavoisier; and the fluid which is collected by the Voltaic trough, and which is probably nothing more than the electric fluid under a peculiar form. Of these, Caloric, as a distinct entity, was detected first. It was found to be a gas of most astonishing energy and activity, and, at the same time, to be of the utmost consequence to the living substance; to exist manifestly wherever life exists, and to disappear on its cessation. It was hence conceived to be the principle of life itself. But oxygene began now to start into notice, and the curious and indispensable part it performs in the respiration, as well as in various other functions * Nam penitus prorsum latet hæc natura, subestque ; of both animal and vegetable existence, to be minutely explored and ascertained, and especially by the microscopic eye of M. Girtanner.* The genius of Crawford fell prostrate before that of Lavoisier. Oxygene was now regarded as the principle of life, and heat as its mere attendant or handmaid. About the year 1790, Professor Galvani, of Bologna, accidentally discovered that the crural nerve of a frog, which had been cut up for his dinner, contracted and became convulsed on the application of a knife wetted with water; and following up this simple fact, he soon discovered also, that a similar kind of contraction or convulsion might be produced in the muscles of other animals, when in like manner prepared for the experiment, not only during life, but for a considerable period after death; and that in all such cases a fluid of some sort or other was either given to the contracting body or taken from it. And professor Volta, about the same period, succeeded in proving that the fluid thus traced to be given or received was a true electric aura; that it might, in like manner, be obtained by a pile of metallic plates, of two or three different kinds, separated from each other by water, * Mémoires sur l'Irritabilité, considerée comme principe de vie dans la nature organisée. Paris, 1790. It is a singular fact, that this identical discovery was not only made, but completed in all its bearings, and by the same means of a recently-dissected frog, by Dr. Alexander Stuart, physician to the queen, in 1732, though no advantage was taken of it. A minute account of Dr. Stuart's experiments is given in the Phil. Trans. for 1732. See the author's Study of Medicine, vol. ii. p. 29. 2d edit. or wetted cloth or wadding; and be so accumulated by a multiplication of such plates, as to produce the most powerful agency in all chemistry. It is not necessary to pursue this subject any farther. Every one has now some knowledge of Galvanism and Voltaism; every one has witnessed some of those curious and astonishing effects which the Voltaic fluid is capable of operating on the muscles of an animal for many hours after death and it only remains to be added, that since the discovery of this extraordinary power, oxygene has in its turn fallen a sacrifice to the Voltaic fluid, and this last has been contemplated by numerous physiologists as constituting the principle of life; as a fluid received into the animal system from without, and stimulating its different organs into vital action. "The identity," says Dr. Wilson Phillip, "of Galvanic electricity and nervous influence is established by these experiments." The result of the whole appears to be, that neither physiology nor chemistry, notwithstanding the accuracy and assiduity with which these sciences have been pursued of late years, has been able to arrest or develope the fugitive principle of life. They have unfolded to us the means by which life, perhaps, is produced and maintained in the animal frame, but they have given us no information as to the thing itself; we behold the instrument before us, and see something of the fingers that play upon it, but we know nothing whatever of the mysterious essence that dwells in the vital tubes, and constitutes the vital harmony. It seems to be on this account, chiefly, that the existence of such a principle as a substantive essence has been of late years denied by MM. Dumas, Bichât, Richerand, Magendie, and, indeed, most of the physiologists of France; whose hypothesis has been caught up and pretty widely circulated in our own country, as though nothing in natural science can be a fair doctrine of belief, unless its subject be matter of clear developement and explanation. But this uncalled for scepticism has involved these philosophers in a dilemma from which it seems impossible for them to extricate themselves, and which we shall have occasion to notice more fully hereafter I mean the existence of powers and faculties without an entity or substantial base to which they belong, and from which they originate. They allow themselves to employ the term, and cannot, indeed, do without it; but after all they mean nothing by it. "No one in the present day," says M. Richerand, "contests the EXISTENCE of a principle of LIFE, which subjects the beings who enjoy it to an order of laws different from those which are obeyed by inanimate beings; by means of which, among its principal characteristics, the bodies which IT ANIMATES are withdrawn from the absolute government of chemical affinities, and are capable of maintaining their temperature at a near degree of equality, whatever be that of the surrounding atmosphere. Its ESSENCE is not designed to preserve the aggregation of constituent molecules, but to collect other molecules which, by assimilating themselves to the organs that IT VIVIFIES, may replace those which daily losses carry off, and which are employed in repairing and augmenting them."* "Personne aujourd'hui ne conteste l'EXISTENCE D'UN PRINCIPE DE VIE qui soumet les êtres qui en jouissent à un ordre That the whole Yet, when we come to examine into the subject more closely, we find that all these terms, so expressive of a specific being and distinct realitythis ESSENCE that VIVIFIES and ANIMATES, has neither being, nor essence, nor vivification, nor animation, nor reality of any kind. of these expressions are metaphysical; and that the word VITAL PRINCIPLE is not designed to express a distinct being, but is merely an abridged formula, denoting the TOTALITY OF POWERS ALONE which animate living bodies, and distinguish them from inert matter, the TOTALITY OF PROPERTIES and LAWS which govern the animal economy.* So that we have here not only the employment of terms that have no meaning, but properties and laws, de lois différentes de celles auxquelles obéissent les êtres inanimés, force à laquelle on pourroit assigner, comme principaux caractères, de soustraire les corps qu'ELLE ANIME, à l'empire absolu des affinités chimiques, auxquelles ils auroient tant de tendance à ceder, en virtu de la multiplicité de leurs élémens; et de maintenir leur température à un dégré presque égal, quelle que soit d'ailleurs celle de l'atmosphère. Son ESSENCE n'est point de conserver l'agrégation des molécules constitutives, mais d'attirer d'autres molécules qui, s'assimilant aux organes qu'ELLE VIVIFIE, remplacent celle qu'entraînent les pertes journalières, et sont employées à les nourrir et à les accroître."- Nouveaux Elémens de Physiologie, tom. i. p. 81. Paris, 8vo. 1804. "Le mot de PRINCIPE VITAL, force vitale, &c. n'exprime point un être existant par lui-même, et indépendamment des actions par lesquelles il se manifeste: il ne faut l'employer que comme une formule abrégée, dont on se sert pour désigner l'ensemble des forces qui animent les corps vivans et les distinguent de la matière inerte : l'ensemble des propriétés et des loix qui régissent l'économie animale.” Id. p. 80. |