590 



METABOLISM 



For these it is best to use a face mask. Unfortunately 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. After being placed^ in position the face mask should be tested for 

 leaks, which can be done by putting soap around the edges. 



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



Fig. 178. Diagram of respiratory valves. 



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 



*This mask has been used extensively by Carpenter. The agent on this continent is TT. N. Elmer, 

 1140 Monadnock Bldg., Chicago. 



