22 



METABOLISM DURING WALKING. 



Pressure conditions. The large volume 

 of air being forced through the air-puri- 

 fying system by the rapidly moving 

 blower created considerable pressure in 

 the system, and a small mercury mano- 

 meter was introduced at the head of the 

 absorber table immediately in front of 

 the soda-lime bottles to act as a safety- 

 valve in case of need. The pressure indi- 

 cated by this manometer when the blower 

 was delivering air at the rate of 100 liters 

 per minute was from 130 to 180 mm. of 

 mercury, depending upon the condition of 

 the soda-lime and the amount of acid in 

 the Williams bottles. From the absorber 

 table to the valve of the mouthpiece, a 

 f-inch galvanized-iron pipe was used and 

 all joints, where practical, were soldered 

 to reduce possibilities of leaks when there 

 was a high pressure on the system. On 

 the return line from the valve to the spiro- 

 meter (see F, fig. 1) the pipe was 6 cm. in 

 diameter, ordinary galvanized-iron con- 

 ductor-pipe being used for the most part. 

 This reduced the pressure so that just 

 beyond the mouthpiece water manome- 

 ters showed a variation in pressure of but 2 to 10 mm. of water, and 

 the opening of a petcock under the spirometer had scarcely any effect 

 on the position of the bell, so evenly balanced was the pressure. 



Adjustment to subject. To permit raising and lowering the con- 

 nections with the subject on the treadmill, a 2-foot length of corru- 

 gated flexible metal tubing was introduced on one side and on the 

 opposite side a rubber hose was inserted (E, fig. 1), 5 cm. in diameter, 

 of about the same length as the metal tubing. This permitted the nec- 

 essary up-and-down adjustment to the height of the subject and the 

 pitch of the treadmill. For conducting the air from the spirometer to 

 the absorber table, rubber tubing 28 mm. in diameter was used. 



Meter. An integrating meter, 1 capable of being read to 10 c. c., 

 was used for measuring the oxygen consumption. As the experimental 

 periods seldom exceeded 12 minutes and the room temperature was 

 fairly uniform, temperature changes were for the most part insignifi- 

 cant, though always measured. The meter was equipped with an 



Fio. 2. Double spirometer. 

 B, main spirometer; A, duplicate 

 spirometer used as reservoir; C, 

 connection with oxygen-supply; D, 

 three-way valve between A and B; 

 E, rubber tubing connecting A 

 andfi. 



J The meter used was made by the American Meter Company, New York, N. Y., their 0.1 

 cu. ft. wet test meter (No. 613), fitted with dial to read in liters. One revolution is equivalent to 

 3 liters, the total reading will run to 1,000 liters, and the volumes may be read to 10 c. c. 



