516 METHODS OF GAS EXCHANGE STUDIES 



exposed to a shower of caustic potash, being thus freed thor- 

 oughly of its moisture and carbonic acid. In the Children's 

 Clinic in Diisseldorf there is a similar apparatus arranged 

 for the study of the gas metabolism of infants. Control ex- 

 periments with combustion of alcohol in this apparatus have 

 shown an average error of 0.4 per cent, in carbonic acid 

 determination, which is to be regarded as a very remarkable 

 performance. 2 



Respiration Calorimeter of Atwater and Benedict. The 

 apparatus of the American physiologists, Atwater and 

 Benedict, is undoubtedly to be regarded as the most com- 

 plete thus far constructed for the study of the respiratory 

 and general metabolism. The respiration chamber of this 

 apparatus is a room provided with a table, bed and folding 

 chair in which the experiment subject may eat, drink, sleep, 

 work and remain for days. The room is surrounded by a 

 double layer of air, there being three walls. There is in- 

 cluded a system of water pipes, very much like a hot water 

 system of heating, which takes away any excess of heat; 

 knowing the amount of water which passes through the 

 apparatus in the course of the experiment and the amount 

 of heat it acquires in passage, the total amount of heat pro- 

 duced can be readily determined. There are, however, ar- 

 ranged in the walls about the respiration chamber ther- 

 mometers and a system of wiring for electrical heating. The 

 thermometers are connected with a galvanoscope, the steadi- 

 ness of which is assurance of the constancy of the tempera- 

 tures during the experiment. An attendant keeps the gal- 

 vanoscope constant throughout, correcting for the least vari- 

 ation, either by altering the current of water circulating 

 through the walls or by the electrical heating appliance. It 

 is not difficult to keep the current of air even in temperature 

 in this way from the time of its admission to its exit from 



2 Zuntz and C. Oppenheimer, Biochem. Zeitschr., 14, 361, 1908; A 

 Schlossmann, C. Oppenheimer and H. Murschhauser, ibid. 



