METHOD FOR DETERMINING RESPIRATORY EXCHANGE IN MAN 



591 



be obtained preserved in salt, and they will keep indefinitely on ice. When needed a 

 short piece is taken, washed free from salt by allowing water from the tap to run 

 through it, and softened in a weak glycerine solution. The gut becomes very soft 

 and pliable, and does not dry quickly. A piece of the casing about 10 cm. long is 

 threaded through a glass tube of about 15 mm. bore and 4 to 6 cm. long. One end 



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

 the valves and mouthpiece are held with a clamp. 



of the casing is brought around the outside of the tubing and secured by means of a 

 thread. The lower end of the membrane is pinched off and the casing is then cut a 

 little more than half way across its middle, so that the opening will lie just within 

 the free end of the tube when the casing is drawn back through it. The loose end of 

 the casing is slightly twisted an essential procedure and is then secured by a thread 

 on the outer side of the tube. If properly made, the valve will work freely without 



