INFLUENCE OF MUSCULAR ACTIVITY. 



Apjolm cites an instance in which the proportion of carbonic 

 acid in the expirations was reduced to 2*9 parts per 100 under 

 the influence of mental depression. 1 



Dr. Hammond could not determine any modification in the 

 exhalation of carbonic acid under the influence of tobacco. 2 



Influence of Sleep. All who have directed attention to 

 the influence of sleep upon the respiratory products have 

 noted a marked diminution in the exhalation of carbonic 

 acid ; but we again recur to the experiments of Dr. Smith 

 for exact information on this point. Dr. Smith estimated 

 the quantity of carbonic acid exhaled during six hours of 

 sleep, at night, at 4,126 cubic inches. According to this 

 observer, the quantity during the night is to the quantity 

 during the day, in complete repose, as 10 is to 18. During 

 a light sleep, the exhalation was 10*32, and during profound 

 sleep, 9 '52 cubic inches per minute. 



"We have alluded to the great diminution in the quantity 

 of oxygen consumed in hibernating animals, while in a torpid 

 condition. Regnault and Eeiset found that a marmot in 

 hibernation consumed only -fa of the oxygen which he used 

 in his active condition. In the same animal they noted an 

 exhalation of carbonic acid equal to but little more than half 

 the weight of oxygen absorbed ; so that in this condition the 

 diminution in the exhalation of carbonic acid is proportion- 

 ately even greater than in the consumption of oxygen. 3 



Influence of Muscular Activity. All observers, except 

 Prout, 4 agree that there is a considerable increase in the 



1 MILNE-EDWARDS, Physiologic, tome ii., p. 535. 



3 Op. cit. 



8 REGNAULT and REISET, Annales de Chimie et de Physique, 3me serie, tome 

 xxvi., p. 446. The marmot consumed in five days 13,088 grammes of oxygen, 

 and exhaled 7,174 grammes of carbonic acid. 



4 Prout only noted the proportion of carbonic acid in the expired air ; and as 

 exercise has the effect of immediately and largely increasing the number of respi- 



