134 



ON THE CIRCULATION OF THE BLOOD, 



jng a certain sweet and saccharine fluid, as the basis of their support, from 

 whatever substances may for this purpose be applied to their respeo^e 

 organs of digestion. Animal chyle and vegetable sap make a very close 

 approach to each other in their constituent principles, as well as in their 

 external appearance. In this respect plants and animals agree. They 

 disagree, inasmuch as animal substances possess a very large proportion 

 of azote, with a small comparative proportif)n of carbone ; while vegeta- 

 ble substances, on the contrary, possess a very large proportion of carbone, 

 with a small comparative proportion of azote. And it is hence obvious, 

 that vegetable matter can only be assimilated to animal by parting with its 

 excess of carbone, and filling up its deficiency of azote. 



Vegetable substances, then, part first of all with a considerable portion 

 of their excess of carbone in the stomach and intestinal canal, during the 

 process of digestion ; a certain quantity of the carbone detaching a cer- 

 tain quantity of the oxygene existing in these organs, as an elementary 

 part of the air or water they contain, in consequence of its closer affinity 

 to oxygene, and producing carbonic acid gas ; a fact which has been 

 clearly ascertained by a variety of experiments by M. Jurine of Geneva. 

 A surplus of carbone, however, still enters the animal system through the 

 medium of the lacteals, and continues to circulate with the chyle, or the 

 blood, till it reaches the lungs. Here again a certain portion of carbone 

 is perpetually parted with upon every expiration, in the form of carbonic 

 i^apour, 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 

 oxygene introduced into the lungs with every returning inspirati<jn ;* while 

 the excess that yet remains is carried oflf by the skin in consequence of its 

 contact with atmospheric air ; a fact put beyond all doubt by the experi- 

 ments and observations of M. Jurine, although, on a superficial view, op- 

 posed by a few experiments of Mr. Ingenhouz,! 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, parl^t 

 with the whole of its excess of carbone. 



Its deficiency of azote becomes suppHed in a two-fold method : firs|, 

 at the lungs ; also, by the process of respiration, as should appear frofla 

 the concurrent experiments of Dr. Priestley and Sir H. Davy, J which 

 agree in showing that a larger portion of azote is inhaled upon every in- 

 spiration, 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 retained oxygene, and perhaps in conjunction 

 with it ; while in union with this economy of the lungs, the skin also 51b- 

 sorbs a considerable quantity of azote, and thus completes the supply that 

 is necessary for the animalization of vegetable food :§ evincing hereby a 



* See Sir H. Davy's Researches Chemical and Philosophical, &c. ; and Memoire sur la 

 Chaleur, par M. M. Lavoisier et De la Place. Mem. de i'Acad. De la Coiubustion, &c. 



t Essaie de Theorie sur 1' Animalization et I'Assimilation des Alimeus, &c., Aunales de 

 Chimie, torn. ii. 



X See Davy's Researches Chemical and Philosophical, &c. and Priestley's Experiments 

 and Observations on diflFerent 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 M. M, Lavoisier and Fourcroy. See Premier Memoire sur la Transpiration des Animaux, 

 par A. Seguin et Lavoisier, 1792 ; and compare with M. Hassenfratz's Memoire s'.ir I» 

 CombinaisonderOxygeue, &c., Acad, des ^ciep, I79L 



