INFLUENCE OF MOISTURE AND TEMPERATURE. 



when muscular exertion is carried so far as to produce great 

 fatigue and exhaustion, the exhalation of carbonic acid is 

 notably diminished. 



Influence of Moisture and Temperature. Lehmann has 

 shown that the exhalation of carbonic acid is much greater 

 in a moist than in a dry atmosphere. 1 This conclusion was 

 the result of a number of experiments on birds and animals 

 confined in air at different temperatures and different degrees 

 of moisture. He found that 35-|- oz. av. weight of rabbits, at 

 a temperature of about 100 Fahr., exhaled during an hour 

 before noon, in a dry air, about 15 cubic inches of carbonic 

 acid ; while in a moist air, at the same temperature, the ex- 

 halation was about 22 cubic inches. 



Disregarding observations on the influence of temperature 

 in cold-blooded animals, as inapplicable to the human sub- 

 ject, it has been ascertained that the exhalation of carbonic 

 acid is much greater at low than at high temperatures, within 

 the limits of heat and cold that are easily borne by the human 

 subject ; thus following the rule which governs the consump- 

 tion of oxygen. Crawford, in his experiments on animal heat, 

 was the first to call attention to this fact. 2 Since then it 

 has been confirmed by numerous observations on animals. 



The experiments of Yierordt on the human subject show 

 that there is an increase in the exhalation of carbonic acid of 

 about one-sixth, under the influence of a moderate diminution 

 in temperature. In these observations, the low temperatures 

 ranged between 37*5 and 59, and the high temperatures be- 

 tween 60*5 and 75'5 Fahr. He found the quantity of air 

 taken into the lungs slightly increased at low temperatures. 

 The absolute quantity of carbonic acid exhaled per minute 

 was 18'2T cubic inches for the low temperatures, and 15*73 

 cubic inches for the high temperatures. 3 



1 LEHMANN, Physiological Chemistry, Philadelphia, 1855, vol. ii., p. 444. 



2 MILNE-EDWARDS, op. cil., p. 548. 



3 Ibid., p. 551. 



