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LECTURE X. 



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



We have distinguished organic from inorganic matter ; and have cha- 

 racterized the former, among other differences, by its being actuated in 

 every separate form by an internal principle, and possessed of parts mu- 

 tually dependent and contributory to each other's functions.- What then 

 is this internal 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 phaenomena 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, Uke him too, wherever it winds its career, is perpetually diffusing 

 around it life and health, and harmony and happiness ? 



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

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

 distinct natures from the present, and to which I shall entreat your atten- 

 tion hereafter ; but confine myself entirely to that inferior but energetic 

 power upon which the identity and individuality of the being depends, and 

 upon a failure of which the individual frame ceases, the organs lose their 

 relative connexion, the laws of chemistry, which have hitherto been con- 

 trolled by its superior authority, assume their action, and the whole system 

 becomes decomposed and resolved into its primary elements. 



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

 occupied 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 day-light, you will not, 1 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 in- 

 herent 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 suc- 

 cessively yielded to its rivals ; and in its turn has re-appeared, under a dif- 

 ferent modification, in some subsequent age, and run through a new stage 

 of popularity. 



For THE SYSTEM OP HARMONY WO are indebted to the inventive genius 

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

 of Lamptus of Erythraea, afterwards of Xenophylus the Pythagorean, and 

 lastly of Aristotle. He was most excellently skilled in music, and is sup- 

 posed to have given the name of harmony to his system from his attach- 

 ment to this science. It is an ingenious and elegant dpgma, and was at 

 one time highly fashionable at Eome as well as at Athens ; and is thm 



