864 EXPERIMENT STATION RECORD. 



chamber serves both the purpose of a window and a door for entrance 

 and exit. 



A current of air is pumped through the apparatus and measured by 

 special devices. Samples of the incoming and outgoing air are taken 

 for analysis. 



An inconvenient rise of temperature is prevented by a current of cold 

 water which passes through a system of pipes inside of the chamber. 

 This device forms a part of the arrangements for measuring the heat 

 given oft' from the body. 



It is desirable to have the incoming current of air as dry as possible. 

 To reduce the water content to a minimum the air which came from out 

 of doors was dried before it entered the chamber by surrounding a por- 

 tion of the pipe through which it passed with a freezing mixture of salt 

 and ice. The aniouirt of water remaining in the incoming air and that 

 in the outgoing air was determined by passing the sample through 

 U tubes filled with puinice stone saturated with concentrated sulphuric 

 acid. The carbon dioxid in the samples of air was determined by 

 passing the air through tubes filled with soda lime. A U tube, con- 

 taining glass beads drenched with barium hydroxid solution, was also 

 used as a control. 



A full description of the different parts of the apparatus is given, 

 and the methods followed in conducting a metabolism experiment are 

 described in detail. 



The subjects of the experiments were a laboratory janitor, a chemist, 

 and a physicist, all young men in good health. The food consisted of 

 a simple mixed diet, which in every case was selected in accordance 

 with the dietary habits of the subject. Two tests were made with the 

 laboratory janitor. In each the subject remained in the respiration 

 chamber 2£ days, although the digestibility of the food was determined 

 for a longer period (4§ days). In the experiment with the chemist the 

 subject remained in the respiration chamber 5 days, and the digestion 

 experiment, which covered several days before the subject entered the 

 respiration chamber, was of 8.| days' duration. In these tests the sub- 

 jects performed no muscular work, and spent their time in reading or 

 resting. 



The experiment with the physicist was of longer duration than the 

 preceding, the subject remaining in the respiration chamber 12 days. 

 The digestibility of the food was determined on several days before 

 the subject entered the chamber and during the experiment, making 

 1G| days in all. The respiration experiment was divided into 5 x>eriods. 

 The first and fifth periods were of If and If days' duration, respec- 

 tively, and were regarded as preliminary and supplementary. The 

 subject avoided both muscular and mental work as much as possible. 

 The remaining periods were each of 3 days' duration. The second 

 was devoted to severe mental labor; the third was spent in absolute 

 rest, the subject avoiding as far as possible all mental and physical 



