EFFECTS OF RESPIRATION ON THE AIR. 527 



increase, and remains stationary as long as they continue to menstruate. When, 

 however, menstruation has ceased, the exhalation of carbonic acid begins again 

 to augment ; and then again diminishes, with the advance of years, as in men. 

 Should menstruation temporarily cease at any time, the exhalation of carbonic 

 acid immediately undergoes an increase, precisely as at the final cessation of the 

 function. And during pregnancy, the exhalation increases in like manner. 

 The following table of the comparative respiration of Females at different ages 

 will serve at the same time for comparison with the preceding, so as to exhibit 

 the general difference between the two sexes, at ages nearly corresponding ; and 

 also to indicate the peculiar modifications induced by the operations of the geni- 

 tal system (Andral and Gavarret) : 



Carbon exhaled Carbon exhaled 



Age. per hour. Age. , . , per hour. 



10 years . . 92.4 grains. 

 13 . . 97.0 



During Menstrual life. During Pregnancy. 



15 years . . 97.0 grains. 22 years . . 129.3 grains. 



26 " . . 97.0 " 32 " . . 126.7 " 



32 " . . 95.4 " 42 " . . 120.3 " 

 45 " . . 95.4 



After Cessation of Catamenia. 



38 years . . 120.3 grains. 66 years . , 104.7 grains. 



49 " . . 113.9 " 76 " . . 101.4 * 



52 . . 115.5 82 " . . 92.4 " 



56 " . . 119.3 " 



d. Development of the Body. The more robust the individual, casteris part- 

 busj the more carbonic acid is exhaled ; and the variation is much more influ- 

 enced by the development of the muscular system, than by the height or weight, 

 capacity of the chest, &c. Thus, a very strong man of twenty-six years of 

 age exhaled at the rate of 217.1 grains per hour; when a man of moderate 

 muscular power set free but 169.4 grains in the same time. Another robust 

 man of sixty years of age exhaled at the rate of 209.4 per hour; another of 

 similar constitution, and sixty-three years of age, at the rate of 190.9 grains 

 per hour ; and an old man of ninety-two years, who still preserved an uncommon 

 degree of energy, and who in his younger days had boasted of extraordinary 

 muscular powers, exhaled at the rate of 135.5 grains per hour. So, also, a 

 remarkably vigorous young woman of nineteen years exhaled at the rate of 107.8 

 grains per hour ; another of twenty-two years, rather less powerful, at the rate 

 of 103.1 grains; and a strong woman of forty-four years (who had ceased to 

 menstruate) 152.4 grains. On the other hand, a slender man of forty-five 

 years, in the enjoyment of good health, only exhaled at the rate of 132.4 grains 

 per hour (Andral and Gavarret). 



e. State of Health or Disease. Upon this very important cause of variation 

 few accurate researches have yet been made. The percentage of carbonic acid 

 in the expired air has been found to be unusually great in the Exanthemata, 

 and in chronic Skin-diseases (Macgregor 1 ) ; and it has been stated to be dimin- 

 ished in Typhus (Malcolm 3 ). Thus, the average proportion in health being 

 about 4.3 per cent. (Vierordt) ; it has been seen at 8 per cent, in confluent Small- 

 pox, at 5 per cent, in Measles, and at 7.2 per cent, in a severe case of Ichthyosis 

 which terminated fatally ; whilst in Typhus the percentage has been found to 

 range from 1.18 to 2.50. But these statements do not indicate the total quan- 

 tity exhaled in each case. The remarkable increase of the exhalation in cases 



1 "Edinb. Monthly Journal," 1843. 2 "Report of Brit. Assoc.," 1843, p. 87. 



