EFFECTS OF RESPIRATION ON TUB AIR. 389 



Hidden increase of temperature occasioned sudden decrease, in an increasing 

 ratio, in the quantity of Carbonic acid evolved, amounting to 1.3 grain per 



sudden 

 ratio, 



minute for 16 Fahr. of temperature; but that in experiments continued 

 over long periods, there was the greatest diversity in the proportion of Car- 

 bonic acid evolved to each degree of temperature. 



II. That the Hygrometric state of the Air influences the rate of exhalation 

 of Carbonic acid, appears from some experiments by Lehmann made with 

 this express view. For he found that while 1000 grammes' weight of Pigeons 

 yielded, in dry air, 6.055 grammes of Carbonic acid per hour, at the tem- 

 perature of 75, and 4.69 grammes at the temperature of 100, the same 

 animals, in moist air, yielded 6.769 grammes at 73, and 7.76 grammes at 

 100. And while 1000 grammes' weight of Rabbits exhaled, in dry air, 

 0.451 gramme per hour, at a temperature of 100, they exhaled as much as 

 0.677 gramme in a moist atmosphere at the same temperature. 1 



in. The amount of Carbonic acid exhaled increases in both sexes up to 

 about the thirtieth year ; it remains stationary until about the forty-fifth ; 

 and it then diminishes. Thus, according to Andral and Gavarret, 2 at 8 years 

 of age, 77 grains of carbon are excreted per hour; at 14 years, 126 grains; 

 at 20 years, 166 grains ; at 48 years, 162 grains ; and at 76 years, 92.4 grains. 



IV. Sex. At all ages beyond eight years, the exhalation is greater in Males 

 than in Females. Nearly the same proportionate increase takes place, how- 

 ever, in Females, up to the time of puberty; when the quantity abruptly 

 ceases to increase, and remains stationary so long as they continue to men- 

 struate. When, however, menstruation has ceased, the exhalation of Car- 

 bonic 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. 



v. Development of the Body. The more robust the individual, cceteris pari- 

 bu*, the more Carbonic acid is exhaled ; and the variation is much more 

 influenced by the development of the muscular system, than by the height 

 or weight, capacity of the chest, etc. Thus a very strong man of twenty-six 

 years of age exhaled at the rate of 217.1 grains of carbon per hour ; while 

 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 ; 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 gra'ins per hour; and a strong woman of forty-five 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). In Dr. Ed. Smith's 

 experiments the quantity of carbon expired per diem to each 1 Ib. of body- 

 weight was 17.07 grains, 17.51 and 17.99, at 48, 39, and 33 years of age re- 

 spectively. 



vi. Nature and Quantity of the Food, and State of the Digestive Process 

 It is well established, that the exhalation of Carbonic acid is greatly increased 

 by eating, and that it is diminished by fasting. Thus Prof. Scharling states 

 the hourly exhalation to have increased in one instance from 145 to 190, 

 after breakfast and a walk ; in another from 140 to 177, after breakfast alone ; 

 and in another from 111.9 to 188.9, after dinner. Dr. Ed. Smith on several 



1 Lehmann, Op. cit., Bd. Hi, p. 304. 2 Annales de Chimie et de Physique, 1843. 



