106 



ON THE PRINCIPLE OP LIFE, 



we find that all these terms, so expressive of a specific being and distinct 

 reality — this essence that vivifies and animates, has neither being, nor 

 essence, nor vivification, nor animation, nor reality of any kind. That 

 the whole 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, powers and principles, without any source, — a super- 

 structure without a foundation, — effects without a cause. 



But what is this curious and delicate instrument itself? — this machine 

 that so nicely responds to the impressions communicated to it, and visibly 

 envelopes so invisible a constituent ? 



It is not my intention in this series of popular study to enter into any 

 minute history of the animal frame, but shall confine myself to those ge- 

 neral views of it which are requisite to show by what means it is operated 

 upon by the delicate powers we have just contemplated, and the more 

 curious phaenomena which result from such an impulse. 



The animal frame, then, is a combination of living solids and fluids, 

 duly harmonized, and equally contributory to each other's perfection. 

 The principle of life, whatever it consists of, exists equally in both : in 

 some kinds in a greater, in others in a less degree. In the fluids, Mr. 

 Hunter has traced it down to their first and lowest stage of existence, for 

 he has traced it in the chyle ;t and there are evident proofs of its accom- 

 panying several of those which are eliminated from the body ; in the blood 

 it is found, as we have already had occasion to notice, in a high degree 

 of activity, and probably in a still higher in the nervous fluid. 



In the solids it varies equally. There are some in which it can scarcely 

 be traced at all, excepting from their increasing growth, as the cellular 

 membrane, and the bones ; in others, we find a perpetual internal activity, 

 or susceptibility to external impressions. But it is in those irritable threads 

 or fibres which constitute the general substance of the muscles or flesh of 

 an animal, that the principle of life exerts itself in its most extraordinary 

 manner, and which it more immediately, therefore, falls within the scope 

 of the present lecture to investigate. 



The muscle of an animal is a bundle of these irritable fibres, or soft, 

 red, cylindrical, and nearly inelastic threads, formed out of a substance 

 which the chemists, from the use to which it is applied, denominate fibrine ; 

 and which, when examined microscopically, are seen to divide and sub- 

 divide, as far as the power of glasses will carry the eye, into minuter bun- 

 dles of fibrils, or still smaller threads, parallel to each other, and bound 

 together by a delicate cellular web-work, obviously of a different nature. 



auroient tant de tendance a ceder, en virtu de la multiplicite de leurs elemens ; et de mainte- 

 nir leur temperature a un degre presque egal, quelle que soit de d'aiileurs celle I'atmosphere. 

 Son ESSENCE n'est point de conserver I'aggregation des molecules constitutives, mais 

 d'attirer d'autres molecules qui, s'assimilant aux organes qu'ELLE viviFiE, remplacent celles 

 qu'entrainent les pertes journalieres, et sont employees a les nourrir et a les accroitre.'' — 

 NouTeaux Elemens de Physiologie, torn. i. p. 81. 8vo. Paris, Svo. 1804. 



* " Le mot de principe vital, force vitale, &c. n'exprime point un etre existant par lui- 

 meme, et independamment des actions par lesquelles il se manifeste : il ne faut I'employer que 

 comma une formule abregee dont on se sert pour designer I'eusemble des forces qui animent 

 les corps vivans et les distin^uent de la matiere inerte :— rensemble des proprietes et des loix 

 qui regisesent I'economie animale." Id. p. 80. 



t On the Blood, p. 91. 



