DESCRIPTION OF APPARATUS. 31 



research with the professional bicycle rider, in which the universal res- 

 piration apparatus was employed, was so successful and the problem of 

 the metabolism during the work of forward progression is so important 

 that, pending the completion and testing of the special calorimeter, the 

 study of this problem with the universal respiration apparatus and the 

 treadmill has seemed entirely justifiable. 



DESCRIPTION OF APPARATUS USED IN THIS RESEARCH. 

 UNIVERSAL RESPIRATION APPARATUS. 



The researches of Zuntz and his co-workers have shown that in walk- 

 ing at a somewhat high rate of speed and carrying a load, the amount of 

 muscular exertion required, even on a level path, is very considerable, 

 approximating that required for bicycle riding under severe stress. 

 Obviously, therefore, any respiration apparatus used in a study of the 

 metabolism under these conditions must be capable of accurately 

 measuring a maximum oxygen consumption per minute of 3,000 c.c. 

 and a maximum carbon-dioxide production of 2,500 c.c. Fortunately 

 the modified form of the universal respiration apparatus employed by 

 Cathcart had already demonstrated its ability to fulfill these conditions. 

 The form of apparatus used in this later research was therefore essen- 

 tially that employed for the earlier study. 1 A general view of the 

 apparatus with its relations to the subject and the accessory apparatus 

 is shown in figure 1. 



Since the completion of the research on the bicycle rider, various 

 minor modifications have been made in the apparatus, chiefly with a 

 view to facilitating operation and contributing to its accuracy. Certain 

 other changes were also necessary to adapt it to the type of experiment 

 planned for this research, namely, walking upon a treadmill at varying 

 rates of speed. These changes were considered of sufficient importance 

 for us to give here a schematic outline of the apparatus as actually 

 employed in the research. (See figure 2.) 



As will be seen from the diagram in figure 2, by turning a 3-way 

 valve N, the subject, breathing through a mouthpiece P, can be con- 

 nected with the ventilating air-current, which is kept in motion by a 

 rotary blower. The air leaving the blower is first passed through a 

 glass Williams bottle which serves as a safety trap against back-suction 

 of acid. The air is next forced through two Williams bottles, each 

 having a capacity of 2.5 liters and half filled with sulphuric acid, 

 which removes the moisture from the air. The ventilating current 

 is then deflected by means of the 2-way valve V 1 into either one of two 



x Brezina and Kolmer in a recent paper from Durig'a laboratory (Biochem. Zeitschr., 1914, 65, p. 

 33) have questioned the accuracy of the respiratory quotients obtained with this apparatus by 

 Benedict and Cathcart in their study of a bicycle rider. Dung in a private communication says 

 that the method used by Benedict and Cathcart for obtaining the respiratory quotients was accu- 

 rate and that the criticisms of Brezina and Kolmer were founded upon an insufficient study of the 

 results. 



