54 CALORIMETERS FOR STUDYING RESPIRATORY EXCHANGE, ETC. 



GENERAL DESCRIPTION OF RESPIRATION APPARATUS. 



This apparatus is designed much after the principle of the Eegnault- 

 Eeiset apparatus, in that there is a confined volume of air in which the 

 subject lives and which is purified by its passage through vessels containing 

 absorbents for water and carbon dioxide. Fresh oxygen is added to this 

 current of air and it is then returned to the chamber to be respired. This 

 principle, in order to be accurate for oxygen determinations, necessitates an 

 absolutely air-tight system and consequently special precautions have been 

 taken in the construction of the chamber and accessories. 



TESTING THE CHAMBER FOR TIGHTNESS. 



As already suggested, the walls are constructed of the largest possible 

 sheets of copper with a minimum number of seams and opportunities for 

 leakage. In testing the apparatus for leaks, the greatest precaution is 

 taken. A small air-pressure is applied and the variations in height of a 

 delicate manometer noted. In cases of apparent leakage, all possible sources 

 of leak are gone over with soapsuds when there is a slight pressure on 

 the chamber. As a last resort, which has ultimately proven to be the best 

 method of testing, an assistant goes inside of the chamber, it is then her- 

 metically sealed, and a slight diminished pressure is produced. Ether is 

 then poured about the walls of the chamber and the odor of ether soon 

 becomes apparent inside of the chamber if there is a leakage. Many leaks 

 that could not be found by soapsuds can be readily detected by this method. 



VENTILATION OF THE CHAMBER. 



The special features of the respiration chamber are the ventilating-pipe 

 system and openings for supplementary apparatus for absorption of water 

 and carbon dioxide. The air entering the chamber is absolutely dry and is 

 directed into the top of the chamber immediately above the head of the 

 subject. The moisture given off from the lungs and skin and the expired 

 gases all tend to mix readily with this dry air as it descends, and the final 

 mixture of gases is withdrawn through an opening near the bottom of the 

 chamber at the front. Under these conditions, therefore, we believe we have 

 a maximum intermingling of the gases. However, even with this system 

 of ventilation, we do not feel that there is theoretically the best mixture of 

 gases, and an electric fan is used inside of the chamber. In experiments 

 where there is considerable regularity in the carbon-dioxide production and 

 oxygen consumption, the system very quickly attains a state of equilibrium, 

 and while the analysis of the outcoming air does not necessarily represent 

 fairly the actual composition of the air inside of the chamber, it evidently 

 represents to the same degree from hour to hour the state of equilibrium 

 that is usually maintained through the whole of a 6-hour experiment. 



