422 KESPIKATIOX. 



diminished ; and in hibernation is so small, that Spallanzani 

 could not detect any difference in the composition of the air 

 in which a marmot, in a state of torpor, had remained for 

 three hours. 1 In experiments on a marmot in hibernation, 

 Regnault and Reiset observed a reduction in the quantity of 

 oxygen consumed to about -$ of the normal standard. 2 



It has been shown by experiments, that the consumption 

 of oxygen bears a pretty constant ratio to the production of 

 carbonic acid ; and as the observations on the influence of 

 sex, number of respiratory acts, etc. on the activity of the 

 respiratory processes, have been made chiefly with reference 

 to the carbonic acid exhaled, we will consider these influences 

 in connection with the products of respiration. 



Experiments on the effect of increasing the proportion of 

 oxygen in the air have led to varied results in the hands of 

 different observers. Regnault and Reiset, whose observa- 

 tions on this point are generally accepted, did not discover 

 any increase in the consumption of oxygen when this gas was 

 largely in excess. 



The results of confining an animal in an atmosphere com- 

 posed of 21 parts of oxygen and Y9 parts of hydrogen are 

 very curious and instructive. When hydrogen is thus sub- 

 stituted for the nitrogen of the air, the consumption of oxygen 

 is largely increased. Regnault and Reiset attribute this to 

 the superior refrigerating power of the hydrogen ; but a more 

 rational explanation would seem to be in its superior diffusi- 

 bility. Hydrogen is the most diffusible of all gases; and 

 when introduced into the lungs in the place of the nitrogen 

 of the air, the vitiated air, charged with carbonic acid, is 

 undoubtedly more readily removed from the deep portions 

 of the lungs, giving place to the mixture of hydrogen and 

 oxygen ; and it is probably for this reason that the quantity 

 of oxygen consumed is increased. It is probable that the 



1 SPALLANZANI, Memoires sur la Respiration, traduites par SENEBIER, Geneve, 

 1803, p. 334. 



9 Op. cit., p. 442. 



