THE RESPIRATION APPARATUS. 23 



The details of manipulation in changing from one absorber system 

 to the other are somewhat important. The first step is to open the 

 valve at the exit end of the new absorber system. This operation, of 

 course, is not carried out until the absorber system has been tested and 

 coupled up, as described on page 32. Inasmuch as there is no tension 

 in the pipe leading from the absorber system to the chamber, this 

 preliminary step does not affect the volume of air. At one-half minute 

 before the end of the experimental period the reading of the pointer on 

 pan No. i ' is recorded, pan No. 2 being in general kept empty. At 

 10 seconds before the end of the experimental period the blower is 

 stopped. The mercury reservoir on the valve connected with the new 

 absorber system is then lowered, and at the exact end of the experi- 

 mental period the reading of the pointer on pan No. i is again recorded. 

 As soon as this is done the wheel on the valve connecting with the 

 new absorber system is opened, and the wheel on the valve connected 

 with the old absorber system is simultaneously closed. The mercury 

 reservoir is then raised to seal the closed valve and the blower is started. 

 The valve at the rear or exit end of the old absorber system is still open, 

 but inasmuch as the air is under no pressure this valve may be closed 

 at leisure. 



APPARATUS FOR THE DETERMINATION OF WATER. 



The water vapor eliminated by the subject through the lungs and 

 skin is removed from the chamber in two ways part of it is condensed 

 within the chamber and collected as drip, but the major part is carried 

 out in the air current as water vapor and removed from the air by 

 dehydration by sulphuric acid. 



COLLECTION OF DRIP. 



Condensation of water vapor within the chamber is due to the method 

 of absorbing and removing the heat eliminated by the subject, as ex- 

 plained on page 125. The apparatus for collecting the drip may be seen 

 in figure 33, on page 124. 



The temperature of the water in the heat-absorbing system is some- 

 times below the dew-point of the air of the chamber. It frequently 

 happens, therefore, especially when the subject is working hard and 

 there is a large quantity of water vapor in the air, that the surface of the 

 heat absorber becomes covered with condensed moisture and the water 

 drips from it. This water is collected in the aluminum shields (Sd in 

 fig- 33) used to regulate the rate of heat absorption, which are pur- 

 posely made water-tight. 



1 For a description of the pans see page 39. 



