428 RESPIRATION. 



subject of an experiment lias an influence upon the products 

 of respiration, and the function is sometimes modified from 

 the mere fact that an experiment is being performed; an in- 

 fluence which Scharling did not fail to recognize, but which 

 frequently cannot be guarded against. 



The observations of Andral and Gavarret were made on 

 sixty-two persons of both sexes and different ages, and under 

 absolutely identical conditions as regards digestion, time of 

 the day, barometric pressure, and temperature. The prod- 

 ucts of respiration were collected in the following way : 

 A thin mask of copper covering the face, and large enough 

 to contain an entire expiration, was fitted to the face by 

 its edges, which were provided with India-rubber, so as to 

 make it air-tight. At the upper part was a plate of glass for 

 the admission of light, and at the lower part an opening, 

 which allowed the entrance of air, but was provided with a 

 valve preventing its escape. By another opening the mask 

 was connected by a rubber tube with three glass balloons, ca- 

 pable of holding 8,544 cubic inches, in which a vacuum was 

 previously established. With the mask fixed upon the face, 

 and a stop-cock opened, connected with the balloons, so as to 

 graduate the current of air, the subject respires freely in the 

 current which comes from the exterior into the receivers. In 

 this way, though the quantity of air respired is not measured, 

 the vacuum in the receivers draws in the products of respira- 

 tion. The current will continue for from 8 to 13 minutes, 

 and is so regulated that the air is respired but once. The 

 quantity of carbonic acid in the receivers represents the 

 quantity produced during the time that the experiment has 

 been going on. 



By carefully fulfilling all the physiological conditions, 



necessity of guarding against the influence of elevation of temperature and accu- 

 mulation of moisture, and attempted to remove the latter by introducing a vessel 

 of sulphuric acid. His greatest difficulty was in the analyses of the air. Though 

 the results obtained are valuable, the process cannot claim the accuracy attained 

 by Andral and Gavarret. 



