102 



ON THE PRINCIPLE OF LIFE, 



cision. When 1 hear an harmonious sound, whatever be its nature. 

 I can distinguish the harmony, though incapable of investigating its 

 cause."* 



I shall only observe, further, that in the doctrine of Mr. (now Sir 

 Humphry) Davy, which holds life itself as a perpetual series of corpus- 

 cular changes, and the substrate, or livmg body, as the being in which 

 these changes take place, we cannot but observe a leaning towards the 

 same system ; and we shall have occasion, in a subsequent lecture, to 

 notice one or two others of equally modern date that touch closely upon 

 it in a few points. t 



Let us pass on, then, to a consideration of the second hypothesis I 

 have noticed, and which consists in regarding the blood itself as the 

 3PR1NCIPLE of life. This opinion lays claim to a still higher antiquity 

 than the preceding ; and, in a general view of the question, is far better 

 founded. It has the fullest support of the Mosaic writings, which ex- 

 pressly appeal to the doctrine, that " the life of all flesh is the blood 

 thereof,"! as a basis for the culinary section of the Levitical code ; a 

 doctrine, indeed, of no new invention even at that early period, but pro- 

 bably derived expressly from the ritual of the higher patriarchs, if we 

 may be allowed to appeal to a similar belief and a similar practice among 

 the Parsees, Hindus, and other oriental nations of very remote antiquity, 

 who seem rather to have draWn this part of their ceremonial directly 

 from the law or tradition of the patriarchs, than indirectly from that of 

 the Jews. 



Among the Greeks and Romans, were the authority of the poets to be 

 of any avail, we should imagine that this hypothesis never ceased to be 

 in reputation ; for the Ti-op^vpeoi damref^ or purple deaths of Homer, and 

 the purpurea anima^ or purple life^ of Virgil, (phrases evidently derived 

 from this theory,) are common-place terms amidst all of them : but the 

 real fact is, that, among the philosophers, we do not know of more 

 than two, Empedocles and Critias, who may be fairly said to have em- 

 braced it. 



In modern times, however, this hypothesis has again dawned forth, and 

 risen even to meridian splendour, under auspices that entitle it to our 

 most attentive consideration. Harvey, to whom we are indebted for a 

 full knowledge of the circulation of the blood, may be regarded as the 

 phosphor of its uprising ; Hoffinan speedily became a convert to the re- 

 vived doctrine ; Huxham not only adopted it, but pursued it with so 

 much ardour, as, in his own belief, to trace the immediate part of the 

 blood in which the principle of life is distinctly seated, and which he sup- 

 posed to be its red particles. But it is to that accurate and truly original 

 physiologist, Mr. John Hunter, that we can only look for a fair restora- 

 tion of this system to the favour of the present day, or for its erection 

 upon any thing like a rational basis. By a variety of important experi- 

 ments, this indefatigable and accurate observer succeeded in proving in- 

 controvertibly that the blood contributes in a far greater degree, not only 

 to the vital action, but to the vital material of the system, than any other 

 constituent part of it, whether fluid or solid. But he went beyond this 

 discovery, and afforded equal proof, not only that the blood is a mean of 



* Du Droit Naturel, Civil, et Politique, torn. i. 154. 

 t Series III. Lecture v. 

 ■: Lent, xvii. 14, 



