ON THE PRINCIPLE OF LIFE, 



LECTURE X. 



ON THE PRINCIPLE OF LIFE, IRRITABILITY, AND MUSCULAR POWER. 



We have distinguisJied org-anic from inorg-anic matter ; and have charac- 

 terized the former, among other differences, by its being actuated in every 

 separate form by an internal principle, and possessed of parts mutually de- 

 pendent and contributory to each other's functions. What then is this in- 

 ternal principle, — this wonderful and ever active power, which, in some sort 

 or other, equally pervades animals and vegetables — which extends from man 

 to brutes, from brutes to zoophytes, from zoophytes to fucuses and confervas, 

 the lowest tribes of the vegetable kingdom, whose general laws and pheno- 

 mena constituted the subject of our last study, — this fleeting and evanescent 

 energy, which, unseen, by the eye, untracked by the understanding, is only 

 known, like its great Author, by its effects ; but which, like him too, wherever 

 it winds its career, is perpetually diffusing around it life and health, and har- 

 mony and happiness 1 



I do not here enter into the consideration of a thinking or intelligent prin- 

 ciple, or even a principle of sensation, both which are altogether of distinct 

 natures from the present, and to which I shall entreat your attention here- 

 after ; but confine myself entirely to that inferior but energetic power upon 

 which the identity and individuality of the being depend, and upon a failure 

 of which the individual frame ceases, the organs lose their relative connexion, 

 the laws of chemistry, which have hitherto been controlled by its superior 

 authority, assume their action, and the whole system becomes decomposed 

 3nd resolved into its primary elements. 



The subject is, indeed, recondite, but it is deeply interesting : it has occu- 

 pied the attention of the wisest and the best of mankind in all ages ; and 

 though, after the fruitless efforts with which such characters have hitherto 

 pursued it, I have not the vanity to conceive that I shall be able to throw 

 upon it any thing like perfect daylight, you will not, I presume, be displeased 

 "with my submitting to you a brief outline of some few of the speculations to 

 which it has given birth, together with the conjectures it has excited in my 

 own mind. 



Of the innumerable theories that have been started upon this subject, the 

 three following are those which are chiefly entitled to our attention. Life is 

 the result of a general harmony or consent of action between the different 

 organs of which the vital frame consists. — Life is a principle inherent in the 

 blood. — Life is a gas, or aura, communicated to the system from without. 

 Each of these theories has to boast of a very high degree of antiquity ; and 

 each, after having had its day, and spent itself, has successively yielded to 

 its rivals; and in its turn has reappeared, under a diffei^ent modification, in 

 some subsequent age, and run through a new stage of popularity. 



For THE SYSTEM OF HARMONY wc are indebted to the inventive genius of 

 Aristoxenus, a celebrated physician of Greece, who was at first a pupil of 

 Lamptus of Erythraea, afterward of Xenophylus the Pythagorean, and lastly 

 of Aristotle. He was most excellently skilled in music, and is supposed to 

 have given the name of harmony to his system from his attachment to this 

 science. It is an ingenious and elegant dogma, and was at one time highly 

 fashionable at Rome as well as at Athens ; and is thus alluded to and ex- 

 plained by Lactantius : " As in musical instruments, an accord and assent of 

 sounds, which musicians term harmony, is produced by the due tone of the 

 Strings ; so in bodies, the faculty of perception proceeds from a connexion 

 and vigour of the members and organs of the frame."* 



To this theory there are two objections, either of which is fatal to it. The 



* V. 140. 



