EXHALATION OF CARBON DIOXIDE. 143 



from the greater number of respiratory movements in early life, that the pro- 

 duction of carbon dioxide, in proportion to the weight of the body, is greater 

 in infancy than in adult life. Direct observations, however, are wanting on 

 this point. 



The observations of Andral and Gavarret show the comparative exhala- 

 tion of carbon dioxide in the male, between the ages of twelve and eighty- 

 two, and give the results of a single observation at the age of one hundred 

 and two years. They show an increase in the absolute quantity exhaled, from 

 the age of twelve to thirty-two ; a slight diminution, from thirty-two to sixty ; 

 and a considerable diminution, from sixty to eighty-two. Taking into con- 

 sideration the increase in the weight of the body with age, it is evident that 

 the respiratory activity is much greater in youth than in adult life, and there 

 can be no doubt that there is a rapid diminution in the relative quantity of 

 carbon dioxide produced in old age. Scharling, in a series of observations 

 on a boy nine years of age, an adult of twenty-eight, and one of thirty-five 

 years, showed that the respiratory activity in the child was nearly twice as 

 great, in proportion to his weight, as the average in the adults. 



Influence of Sex. All observers have found a marked difference between 

 the sexes, in favor of the male, in the proportion of carbon dioxide exhaled. 

 Andral and Gavarret noted an absolute difference of about forty- five cubic 

 inches (737*4 c. c.) per hour, but did not take into consideration the differ- 

 ences 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 important difference connected with the variations with 

 age, which depends upon 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 occur with regular- 

 ity (Andral and Gavarret). During this time the average exhalation per 

 hour is 714 cubic inches (11*69 litres). After the cessation of the menses 

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

 cubic inches (15 litres) per hour. From the age of sixty to eighty-two the 

 quantity diminishes to 793 (13 litres), and finally to 670 cubic inches (about 

 11 litres). When the menses are suppressed, there is an increase in the 

 exhalation of carbon dioxide, which continues until the flow becomes reestab- 

 lished. In a case of pregnancy observed by Scharling the exhalation was 

 increased to about 885 cubic inches (14-5 litres). 



Influence of Digestion. Almost all observers agree that the exhalation of 

 carbon dioxide is largely increased during digestion. Lavoisier and Seguin 

 found that in repose and fasting, the quantity exhaled per hour was 1,210 

 cubic inches (19*82 litres), which was raised to 1,800 and 1,900 (29*5 and 

 31-14 litres) during digestion. A series of observations on this point was 

 made by Vierordt upon his own person. Taking his dinner between 12*30 



