428 NUTRITION. 



all animals, even those lowest in the scale, appropriate oxy- 

 gen and eliminate carbonic acid ; and this is equally true of 

 all living tissues. In 1775, Lavoisier noted the fact that the 

 gas obtained by decomposing the oxide of mercury was more 

 active than the air in maintaining the respiration of animals. 1 

 Two years later, he compared oxidation by respiration in 

 animals to ordinary combustion, and advanced the hypothe- 

 sis that this action was the cause of the constant temperature 

 of animals of about 32|- Reaumur. 2 A little later, he pub- 

 lished the remarkable experiments in which he estimated 

 the amount of " combustion " in a Guinea-pig, by collecting 

 the carbonic acid exhaled, and compared it with the amount 

 of heat lost by the same animal in a definite time. 3 Here 

 he met with some difficulty, and found that the heat pro- 

 duced, according to his calculations, did not quite equal the 

 heat lost. In later memoirs he ascertained positively that 

 the carbonic acid exhaled in respiration did not represent 

 the totality of the oxygen consumed ; and he attributed the 

 production of heat in part to the union of oxygen with hy- 

 drogen. 4 Since it has been ascertained that oxygen is dis- 

 solved, as oxygen, in the arterial blood, that it disappears in 

 part or entirely in the capillary circulation, that carbonic 

 acid is taken up by the venous blood, both in solution and in 

 feeble combination in the bicarbonates, to be discharged in 

 the lungs by displacement and the action of the pneumic 



1 LAYOISIER, Memoire sur la nature du principe qui se combine avec les metaux 

 pendant leur calcination, et qui en augmente lepoids. Histoire de V academic royale 

 des sciences, annee, 1775, Paris, 1778, pp. 521, 525. 



2 LAVOISIER, Memoire sur la combustion en general. Histoire de V academic 

 royale des sciences, annee, 1777, Paris, 1780, p. 599. 



3 LAVOISIER ET DE LA PLACE, Memoire de la ckaleur. Histoire de Vacademie 

 royale des sciences, annee, 1780, Paris, 1784, p. 407. 



4 LAVOISIER, Memoire sur les alterations qui arrivent d Fair dans plusieurs 

 circonstances ou se trouvent les Jiommes reun'ts en societe. Histoire de la societe 

 royale de medecine, annees, 1782 et 1783, Paris, 1787, p. 574. 



SEGUIN ET LAVOISIER, Premier memoire sur la respiration des animaux. 

 Histoire de Vacademie royale des sciences, annee, 1789, Paris, 1793, p. 566, 

 et seq. 



