201 



the due circulation and distribution of the blood, 

 and is more or less affected by all its variations *. 



158. In the inferior animals we have seen (142.3.) 

 that the production of carbonic acid, and consequently 

 of carbon, is very much influenced by external tempe- 

 rature, as this more or less affects the circulation of 

 the blood : and even in the human subject, it has been 

 shewn (152.), that the same causes possess a decided 



* Long since this opinion concerning the source of the carbon 

 furnished in animal respiration, was entertained by the author, 

 his friend Dr Nugent has pointed out to him a passage in a 

 French writer, wherein a similar notion is distinctly stated. The 

 author, M. Caron, in opposing the opinion of Dr Goodwyn con- 

 cerning the entrance of oxygen gas into the blood-vessels, and 

 the emission of carbonic acid from them, has these words : " Je 

 vais demander ici a nos chymistes modernes, si, pour qu'il se 

 forme de Pair fixe dans la respiration, il ne suffit pas que Pair 

 vital puisse se charger, se souler de Phumeur qui sort des vaisseaux 

 exhalans des poumons : pour moi, je crois que cet effet pent 

 s'operer tout bonnement de cette maniere, sans que Pair vital 

 communique en quelque chose avec le sang : Je suis d'autant plus 

 fpnde a le croire, que Goodwyn, ainsi que tous les chymistes mo- 

 dernes, avouent qu'ils ne connoissent pas encore la route que 

 Poxigene peut prendre pour y parvenir, ni par quelle vertu jl 

 peut agir sur kii." In a subsequent paragraph also, he asks, 

 whether, instead of saying with Goodwyn, that a certain quanti- 

 ty of oxygen gas is separated from the inspired air in the lungs 

 by respiratidn, and a certain quantity of carbonic acid substituted 

 in its place, it would not be better to say : " Une certaine 

 quantite de gaz oxigene constituante Pair atmospherique, se 

 charge dans les poumons d'une certaine quantite de Phumeur de 

 la respiration, qui le metamorphose, et en change tellement la na- 

 ture, que Poxigene n'est plus reconnoisable, et qu'il est devenu 

 fl'acide carbon i que *." 



* Recherches Critiques, par J. C. F, Caron, p. 29, 51. an, 1798, 



