152 RESPIRATION 



pidity and increased depth more CO2 is exhaled than under 

 opposite conditions. 



The amount of CO exhaled is small in very young in- 

 fants. But soon the output begins to increase, and in males 

 continues to do so up to about thirty years ; there is then a 

 slight decrease up to sixty, and afterward a considerable de- 

 crease to death. 



In the female the output is less than in the male. In the 

 former sex the increase is said to cease at puberty and to 

 remain constant until the menopause, after which time it in- 

 creases to sixty and diminishes subsequently. 



During digestion the quantity is considerably increased. 

 This is probably due to the muscular activity of the alimen- 

 tary tract, to glandular metabolism and to changes taking 

 place in the food products. 



As to diet, it may be said in general that the exhaled CQz 

 is increased in quantity by the taking of nitrogenized foods, 

 tea and coffee. 



The influence of sleep is to diminish the output. 



Muscular exercise is very efficient in increasing the 

 amount of CCte exhaled ; in fact, this explains partly the va- 

 riations in connection with sex, digestion, sleep, etc. 



A high degree of moisture increases the exhalation, as 

 does a rise in body temperature. A rise in external tempera- 

 ture, however, has an opposite effect. 



The output is increased in spring and decreased in autumn. 



When the efferent nerve supplying a part is severed the 

 production of COs in that part is at once diminished. 



The consumption of O and the exhalation of CCte bear a 

 fairly constant relation to each other any condition in- 

 creasing one increasing the other, and vice versa. The 

 facts, therefore, which have been mentioned as governing 

 the exhalation of CO2 may be applied to the consumption 

 of O. 



(c) Gain in Temperature. When the body temperature 

 is normal and the external atmospheric temperature about 



