METHOD FOR DETERMINING RESPIRATORY EXCHANGE IN MAN 



557 



The bell is counterpoised by means of a weight. In the original Tissot 

 spirometer an automatic adjustment permitted water in amount equal 

 to the water displaced by the bell to flow from the spirometer cylinder 

 into a counterpoise cylinder as the bell ascended out of the water. 



Fig. 179. The Tissot spirometer. In actual experiment, subject is reclining or lying down and 

 the valves and mouthpiece are held with a clamp. 



The bell, being heavier out of water than when it is immersed, is accord- 

 ingly counterpoised in any position, although Carpenter has shown that 

 this refinement is unnecessary. An opening in the top of the spirometer 

 permits the insertion of a rubber stopper, through which are passed a 

 thermometer, a water manometer, and a stopcock with tube for drawing 



