537 



In the original bag method of Regnard the subject breathed through a 

 Denayrouse mouth-piece and a pair of valves into a rubber sack of about 

 200 liters capacity. At the end of an observation a sample of about 150 

 c.c. of air was withdrawn for analysis and the balance of the contents was 

 passed slowly through a series of absorbers and through a gas meter. In 

 the Douglas method as originally described a mica or rubber-flap valve 

 was used in connection with a mouth-piece and a tube of 20 mm. 

 diameter led to a three-way valve of large bore which was connected with 



Fig. 16. Spirometer of Boothby and Sandiford as used in the. writer's laboratory. 

 Sampling tubes are shown on shelf above the wheels. 



a wedge-shaped reservoir bag made of rubber-lined cloth (Fig.. 17). This 

 form of bag is more impervious than rubber and therefore "more reliable. 

 The shape of the bag permits it to be rolled up and emptied completely. 

 The expired air is measured at the end of an observation by passing it 

 through a meter and a sample is analyzed. By supporting the tube and 

 valves on a light framework upon the head and resting the bag on an- 

 other frame placed on the back the apparatus is made adaptable to a march- 

 ing experiment. 



It has proved especially valuable in mountain climbing (Ilaldane, 

 Henderson, et al.) and other forms of open-air exercises. With violent 

 exercise a bag holding 60 liters will not take the air expired during one 



