116 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



representing the nearest millimeter. It so happens that in the work 

 with the diet squads we had occasion to use only the 60 and 40 mm. 

 disks. 



The tests with the subsidiary chamber showed that a definite pro- 

 portion of the carbon dioxide admitted was invariably recovered in the 

 soda-lime bottle, this amount being constant for the individual disk 

 used in the main discharge opening, but varying with the size of the 

 disk. Furthermore, it was found that the amount of carbon dioxide 

 collected in both sets of absorbers was invariably the same, proving 

 that the discharge of air through the two 10-mm. openings was 

 identical. 



With the subsidiary chamber various other tests were made to study 

 the influence of both slightly decreased and slightly increased pressure 

 on the intake side of the main blower. Furthermore, since variations 

 in line voltage are to be expected with consequent change in shaft 

 speed, it was important to note whether such changes affected the ali- 

 quot or not. Changes in line voltage and shaft speed of the blower 

 were therefore studied, but the aliquoting device of the wind chest with 

 its three openings showed invariably the same proportion of air dis- 

 charged through the individual openings. 



All of the preliminary tests were carried out with the subsidiary 

 chamber. After the tests were completed and the sampling apparatus 

 attached to the group respiration chamber, quantitative tests were 

 made by introducing hquefied carbon dioxide into the larger chamber. 

 With the subsidiary chamber the residual air could be considered as 

 atmospheric, inasmuch as but a few seconds were required to ventilate 

 the chamber completely and sweep out any carbon dioxide admitted. 

 But in the tests with the group chamber it was necessary to make 

 residual analyses of the air inside the chamber at the beginning and end 

 of each test, as with the disks 60 mm. or less in diameter, a long time 

 would be required to sweep out completely the carbon dioxide ad- 

 mitted and reduce the percentage of carbon dioxide in the air to that 

 of outside air. 



These tests have been repeated many times throughout the two years 

 that the apparatus was in the process of development and a standard 

 factor found for each size of disk to indicate the percentage of the total 

 carbon dioxide withdrawn from the chamber which was collected in the 

 soda-lime bottles, due correction being made for the carbon dioxide in 

 the ingoing air. The ratio for the individual disks was invariably con- 

 stant, irrespective of the chamber used, barometric pressure, speed of 

 admitting carbon dioxide, and shaft speed of the rotary blower and 

 consequent pressure inside the wind chest; at least, the ratios were con- 

 stant within the ranges of pressure change possible with the rotary air- 

 impeller, for we deal here with actual pressures corresponding to no 

 more than those equivalent to a few millimeters in water pressure. 



