EXHALATION OF CAKBONIC ACID. 429 



regulating the number of respirations, as far as possible, to 

 the normal standard, different observations on the same sub- 

 ject, at different times, under the same conditions, were at- 

 tended with results so nearly identical, as to give every con- 

 fidence in the accuracy of the process. But even then, these 

 observers recognized such immense variations in the exhala- 

 tion of carbonic acid with the constantly varying physiologi- 

 cal conditions, that they did not feel justified in taking their 

 observations as the basis for calculations of the entire quantity 

 exhaled in the twenty-four hours. 



The results of these observations on the male, between the 

 ages of sixteen and thirty, between 1 and 2 P.M., under iden- 

 tical conditions of the digestive and muscular systems, each 

 experiment lasting from eight to thirteen minutes, showed an 

 exhalation of about 1,220 cubic inches of carbonic acid per 

 hour. 



Dr. Edward Smith, 1 in his elaborate paper on the phe- 

 nomena of respiration, employed a very rigorous method for 

 the estimation of the carbonic acid exhaled. He used a 

 mask, fitting closely to the face, which covered only the air- 

 passages. The air was admitted after being measured by 

 passing through an ordinary dry gas-meter. The expired 

 air was passed through a drying apparatus, and the carbonic 

 acid absorbed by a solution of potash, arranged in a number 

 of layers, so as to present a surface of about 700 square inches, 

 and carefully weighed. This apparatus was capable of col- 

 lecting all the carbonic acid exhaled in an hour. The esti- 

 mate was made for 18 waking hours and 6 hours of sleep. 

 The observations for the 18 hours were made on four persons, 

 namely: Dr. Smith, set. 38 years, weighing 196 pounds, 6 

 feet high, with a vital capacity of 280 cubic inches ; Mr. 

 Ghouls, set. 48 years, 5 feet 9^- inches high, 175 pounds 

 weight ; Dr. Murie, set. 26 years, 5 feet TJ inches high, 133 

 pounds weight, vital capacity 250 cubic inches ; Prof. Frank- 

 land, set. 33 years, 5 feet 10|- inches high, and 136 pounds 



1 Loc. tit. 



