128 RESPIRATION 



absorbed is equal to about five per cent of the volume of air inspired, 

 and the carbon dioxide exhaled, only about four per cent A part of 

 the deficiency in volume of the expired air is to be accounted for, then, 

 by a deficiency in the exhalation of carbon dioxide. 



The experiments of Regnault and Reiset have an important bearing 

 on the question under consideration. As these observers were able to 

 measure accurately the quantities of oxygen consumed and carbon 

 dioxide produced in a given time, the relation between the two gases 

 was kept constantly in view. They found great variations in this rela- 

 tion, dependent mainly on the regimen of the animal. The total loss 

 of oxygen was found to be greater in carnivorous than in herbivorous 

 animals ; and in animals that could be subjected to a mixed diet, by 

 regulating the food this was made to vary between the two extremes. 

 The mean of seven experiments on dogs showed that for every 1000 

 parts of oxygen consumed, 745 parts were exhaled in the form of carbon 

 dioxide. In six experiments on rabbits, the mean was 919 for every 

 1000 parts of oxygen. 



In animals fed on grains, the proportion of carbon dioxide exhaled 

 was greatest, sometimes passing a little beyond the volume of oxygen 

 consumed. 



"The relation is nearly constant for animals of the same species 

 when subjected to a uniform alimentation, as is easy to realize as re- 

 gards dogs ; but it varies notably in animals of the same species, and 

 in the same animal, submitted to the same regimen, but in which we 

 can not regulate the alimentation, as in fowls." 



When herbivorous animals were deprived of food, the relation be- 

 tween the gases was the same as in carnivorous animals. 



The final result of the experiments of Regnault and Reiset was that 

 the " relation between the oxygen contained in the carbon dioxide and 

 the total oxygen consumed, varies, in the same animal, between 0.62 

 and 1.04, according to the regimen to which it is subjected." These 

 observations on animals have been confirmed in the human subject by 

 Doyere, who found great differences in the relations of the two gases in 

 respiration ; the volume of carbon dioxide exhaled varying between 

 0.862 and 1.087 f r l P ai "t of oxygen consumed. 



As regards the destination of the oxygen that is not represented in 

 the carbon dioxide exhaled, it is certain that a part of it, at least, unites 

 with hydrogen to form water, this contributing to the production of 

 animal heat, a question that will be fully discussed in another connec- 

 tion. 



The variations in the relative volumes of oxygen consumed and 

 carbon dioxide produced in respiration are not favorable to the hypothe- 



