On the Structure and Functions of the Organs of Respiration. 217 



observe such contrivances in the internal structure of an organ, any more 

 tlian in the adaptation yf a peculiar modification of organ to the habits of 

 the animal to whom it belongs, without becoming aware that these same 

 facts, from which, when collected, any truth of physical science is deduced, 

 admit also of a deduction of precisely the same strength, concerning the 

 wisdom and intelligence of their Contriver. These conclusions, as Lord 

 Brougham has clearly shewn, rest upon one and the same series of facts, 

 and are deduced by one and the same process of reasoning ; and not only 

 cannot we, with any degree of fairness, retain the physical and reject the 

 theological induction, but he who demonstrates the one may be fairly 

 charged with a sort of anti-theistical partiality, if he wilfully obscures the 

 other. 



ON THE STRUCTURE AND FUNCTIONS OF THE ORGANS 

 OF RESPIRATION, 



IN THE ANIMAL AND VEGETABLE KINGDOMS. 



The tendency to change is one of the most constant and striking charac- 

 teristics, by which organised substances may be distinguished from inert 

 matter. It is especially manifested in the living body, where it is applied 

 to the maintenance of the system, under the controul of certain laws, which, 

 from our complete ignorance of their nature, we can only characterise as 

 vital ; but we also observe the same tendency in the dead state of organised 

 matter, causing the spontaneous decomposition of complex proximate prin- 

 ciples into their ultimate elements or simple combinations of them. In 

 the latter instance, the changes which take place are under the direct and 

 evident action of the laws of chemical affinity ; but the nature of those 

 which occur in the living body is by no means so well understood j and 

 although modern researches in Chemistry* have done much to prove that 

 the laws of affinity, which govern inert matter, are also active in the organ- 

 ised body, yet we are constrained to admit the existence of a governing 

 power, by which these laws are brought into exercise, and their extraordinary 

 results controuled. And since on the existence of this power depends the 

 continuance of the activity of the system, whether in plants or animals, 

 its capability of maintaining its normal condition amidst a great variety of 

 external circumstances, and its preservation from spontaneous decomposi- 

 tion, it is usually termed the vital principle. 



• " Chemistry," says Dr. Roget, " notwithstanding the prourt rank it justly holds 

 among the physical sciences, and the noble discoveries with which it has enriched 

 the arts ; notwithstanding it has unveiled to us many of the secret operations of na- 

 ture, and placed in our hands some of her most powerful instruments for acting on 

 matter ; and notwithstanding it is armed with full powers to destroy — cannot, in any 

 one organic product, rejoin that which has been once dissevered." — Bridgewater 

 Treatise on Physiology, vol. ii, p. 5. 



