METHOD FOR DETERMINING RESPIRATORY EXCHANGE IN MAN 



555 



spring, and serves to hold the spring tightly clamped on the nostrils in 

 the proper position (see Fig. 177). 



Some individuals experience great distress when made to breathe 

 through the mouth. For these it is best to use a face mask. Unfortu- 

 nately at the present time no mask is entirely satisfactory. Perhaps the 

 best is one sold by Siebe, Gorman & Co.,* which is pictured in the cut. 



Fig. 177. A, Nose clip; B, Face mask; C, Mouth piece. 



After being placed in position the face mask should be tested for leaks, 

 which can be done by putting soap around the edges. 



2. THE VALVES. The valves of Tissot are probably the best for the 

 purpose, but they are expensive and difficult to obtain. We have made 

 perfectly satisfactory valves from the prepared casings used in the 

 manufacture of bologna sausage. These can be obtained preserved in 

 salt, and they will keep indefinitely on ice. When needed a short piece 



*This mask has been used extensively by Carpenter. The agent in this country is II. X. Klmer, 

 1140 Monadnock Bldg., Chicago. 



