124 RESPIRATION 



take into consideration differences in the weight of the body. Scharling, 

 taking the proportion exhaled to the weight of the body, noted a marked 

 difference in favor of the male. The difference in muscular activity in 

 the sexes is sufficient to account for the greater elimination of carbon 

 dioxide in the male, for this substance is exhaled in proportion 

 to the muscular development of the individual ; but there is an im- 

 portant difference connected with the variations with age, which de- 

 pends on the condition of the generative system of the female. The 

 absolute increase in the exhalation of carbon dioxide with age in the 

 female is arrested at the time of puberty and remains stationary until 

 the cessation of the menses, provided the menstrual flow occurs with 

 regularity. During this time the average exhalation per hour is 714 

 cubic inches (11.69 liters). After the cessation of the menses the 

 quantity gradually increases, until, at the age of sixty, it amounts to 915 

 cubic inches ( 1 5 liters) per hour. From the age of sixty to eighty-two 

 the quantity diminishes to 793 (13 liters), and finally to 670 cubic inches 

 (about 1 1 liters). When the menses are suppressed, there is an increase 

 in the exhalation of carbon dioxide, which continues until the flow be- 

 comes reestablished. In a case of pregnancy observed by Scharling the 

 exhalation was increased to about 885 cubic inches (14.5 liters). 



Influence of Digestion. Lavoisier and Seguin found that in repose 

 and fasting, the quantity of carbon dioxide exhaled per hour was 1210 

 cubic inches (19.82 liters), which was raised to 1800 and 1900 (29.5 and 

 31.14 liters) during digestion. A series of observations on this point 

 was made by Vierordt upon his own person. Taking his dinner between 

 12.30 and i P.M., having noted the frequency of the pulse and respirations 

 and the exhalation of carbon dioxide at 12 M., he found at 2 P.M., the 

 pulse and respirations increased in frequency, the volume of expired air 

 augmented, and the carbon dioxide exhaled increased from. 15.77 to 

 18.22 cubic inches (258.43 to 298.6 cubic centimeters) per minute. In 

 order to ascertain that this variation did not depend on the time of day, 

 independently of the digestive process, he made a comparison at 12 M., 

 at i and at 2 P.M. without taking food, which showed no notable varia- 

 tion, either in the pulse, number of respirations, volume of expired air 

 or quantity of carbon dioxide exhaled. 



The effect of inanition is to diminish the exhalation of carbon dioxide. 

 Bidder and Schmidt noted the daily production in a cat subjected to 

 eighteen days of inanition, at the end of which time it died. The 

 quantity diminished gradually from day to day, until just before death 

 it was reduced by a little more than one-half. Edward Smith noted in 

 his own person the influence of a fast of twenty-seven hours. There 

 was a marked diminution in the quantity of air respired, in the quantity 



