534 



JOHN R. MURLIN 



Fig. 12. The half mask as used by Boothby. 



c. Collecting Apparatus. The expired air can be collected either in 

 a spirometer (Speck(&), Tissot), in a bag (Regnard, Douglas, C. G.), or 



Fig. 13. Air valve of Loven. 



it may be measured by means of a gas meter and simultaneously sampled 

 for analysis (Geppert(a)). 



In the original spirometer method of Speck the inspired air was drawn 

 from one spirometer and the expired air forced into another so that the 

 difference in volume of inspired and expired air could be recorded and the 



