143 



ON THE CIRCULATION OF THE BLOOD, 



to circulate with the chyle, or the blood, till it reaches the lungs. Here again 

 a certain portion of carbon is perpetually parted with upon every expiration, 

 in the form of carbonic vapour, according to Mr. Ellis, but according to Sir 

 H. Davy and others, in that of carbonic gas, in consequence of its union 

 with a part of the oxygen introduced into the lungs with every returning in- 

 spiration ;* while the excess that yet remains is carried off by the skin, in 

 consequence of its contact with atmospheric air : a fact put beyond all doubt 

 by the experiments and observations of M. Jurine, although on a superficial 

 view, opposed by a few experiments of Mr. Tngenhouz,t and obvious to every 

 one, from the well-known circumstance that the purest linen, upon the purest 

 skin, in the purest atmosphere, soon becomes discoloured. 



In this way, then, and by this triple co-operation of the stomach, the lungs, 

 and the skin, vegetable matter, in its conversion into animal, parts with the 

 whole of its excess of carbon. 



Its deficiency of azote becomes supplied in a twofold method : first, at the 

 lungs ; also, by the process of respiration, as should appear from the concur- 

 rent experiments of Dr. Priestley and Sir H. Davy,J which agree in showing 

 that a larger portion of azote is inhaled upon every inspiration than is returned 

 by every succeeding expiration; in consequence of which the portion retained 

 in the lungs seems to enter into the system, in the same manner as the re- 

 tained oxygen, and perhaps in conjunction with it ; while, in union with this 

 economy of the lungs, the skin also absorbs a considerable quantity of azote, 

 and thus completes the supply that is necessary for the animalization of 

 vegetable food :^ evincing hereby a double consent of action in these two 

 organs, and giving us some insight into the mode by which insects and worms, 

 which are totally destitute of lungs, are capable of employing the skin as a 

 substitute for lungs, by breathing through the spiracles existing in the skin 

 for this purpose, or merely through the common pores of the skin, without 

 any such additional mechanism. It is by this mode, also, that respiration 

 takes place through the whole vegetable world, offering us another instance 

 of resemblance to many parts of the animal ; in consequence of which, 

 insects, worms, and the leaves of vegetables equally perish by being smeared 

 over with oil, or any other viscous fluid that obstructs their cutaneous orifices. 



But to complete the great circle of universal action, and to preserve the 

 important balance of nature in a state of equipoise, it is necessary, also, to 

 inquire by what means animal matter is reconverted into vegetable, so as to 

 afford to plants the same basis of nutriment which plants have previously 

 afforded to animals 1 



Now this is for the most part obtained by the process of putrefaction, or 

 a return of the constitut'iit principles of animal matter to their original affini- 

 ties, from which they have been inflected by the superior control of the vital 

 principle, so long as it inhabited the animal frame, and coerced into other 

 combinations and productions. || Putrefaction is, therefore, to be regarded 

 as a very important link in the great chain of universal life and harmony. 



The constituent principles of animal matter we have already enumerated : 

 they are most of them compound substances, and fall back into their respec- 

 tive primordia as the putrefactive process sets them at liberty. This process 

 commences among the constituent gases ; and it is only necessary to notice 

 the respective changes that take place in this quarter, as every other change 

 is an induced result. 



* See Sir H. Davy's Researches Chemical and Philosophical, &c. ; and M^moire sur la Chaleur, par 

 MM. Lavoisier et De la Place. Mem. de I'Acad. De la Combustion, &c. 



t Essaie de Th^orie sur 1' Animalization ct I'Assimilation dcs Alimens, &c. Annales de Chimie, torn. ii. 



t See Davy's Researches Chemical and Philosophical, &c. ; and Priestley's Experiments and Observa- 

 tions on different Kinds of Air, vol. iii. 



§ M. Jurine is chiefly entitled to the honour of this discovery : his experiments coincide with several of 

 Dr. Priestley's results, and have been since confirmed by other experiments of MM. Lavoisier and Fourcroy 

 See Premier Memoire sur la Transpiration des Animaux, par A. Seguin et Lavoisier, 1792; and compaie 

 with M. Hassenfratz's M6moire sur la Combinaison de TOxygen, &c. Acad, des Scien. 1791. 



II It should hence appear, that putrefaction is the only positive criterion of death, or the total cessation 

 of the principle of life. Galvanism has, indeed, been advanced as a decisive proof of the same by Betrenda 

 and Creve ; but Humboldt has sufficiently shown its insecurity as an infallible test. 



