CHAPTER XXXVI 



METHODS FOR THE DETERMINATION OF THE RESPIRATORY 



EXCHANGE 



THE respiratory exchange can be measured by collecting the 

 expired air in canvas-rubber bags. The bags are large so that 

 the air expired by a resting man for periods of half an hour may 

 quite conveniently be collected. When it is required to determine 



Fio. 179. APPARATUS USED FOR DETERMINING THE TOTAL RESPIRATORY CHANGE 

 IN MAN. (C. G. Douglas.) 



4 



the exchange during exercise, such as walking, running, swim- 

 ming, etc., smaller bags may be used, and the air of one or two 

 minutes' breathing collected. The subject of the experiment wears 

 a mouthpiece fitted with inspiratory and expiratojk valves. The 

 nose is closed by a clip. By means of the val^^ the outside 



317 



