14 COMPARISONS OF RESPIRATORY EXCHANGE. 



tance of a graphic record of the degree of muscular rest on the part of 

 the subject has been very thoroughly emphasized. Various methods 

 of obtaining such a record have been employed in this research, which 

 are subsequently described. Most of the men in these comparison tests 

 were trained subjects and accustomed to keeping quiet during such 

 experiments; the untrained subjects were also particularly instructed 

 to refrain from all movements of body and limbs during the time of the 

 experiment. 



The apparatus used were the bed respiration calorimeter, the two 

 types of the Benedict universal respiration apparatus, the Zuntz- 

 Geppert valves, meter, and gas-analysis apparatus, the Tissot nose- 

 pieces, valves, and spirometer, the Douglas bag and mica-flap valves, 

 the Mueller valves, two forms of the Haldane gas-analysis apparatus, 

 and a small hand spirometer. A detailed description of these appa- 

 ratus follows. 



BED RESPIRATION CALORIMETER. 



The bed respiration calorimeter used in this research is in principle 

 like the chair calorimeter which has been described in detail elsewhere. 1 

 It has all the features of that apparatus, but the form of the chamber 

 is particularly adapted to experiments with subjects in a reclining 

 position. 



The general principle of the apparatus is that of a closed-circuit 

 system, consisting of a chamber with a ventilating apparatus attached. 

 The ventilating apparatus removes the air continually from the 

 chamber and provision is made for absorbing the water- vapor and the 

 carbon dioxide from the air-current and for admitting oxygen to replace 

 that used by the subject. 



The general arrangement of the chamber and ventilating apparatus 

 is shown in figure 1. The interior portion of the chamber consists 

 of a copper shell, which is rigidly attached to a steel framework. 2 

 In horizontal cross-section it is rectangular in shape and in vertical 

 cross-section it is trapezoidal. The length is 220 cm., the width 

 76 cm., and the height 71 cm. in front and 41 cm. at the back. Its 

 volume is about 950 liters. A rectangular opening at the front, 

 70 cm. wide and 47 cm. high, permits placing inside a subject lying 

 upon a mattress. This opening is closed by a pane of plate glass, which 

 is held in place and sealed air-tight by means of a soft wax of special 

 composition seared over with a soldering iron. 



The ventilation of the chamber is maintained by means of a rotary 

 blower, 3 F, which draws the air from the chamber and forces it through 



'Benedict and Carpenter, Carnegie Inst. Wash. Pub. 123, 1910. 



2 Since this was written, the bed calorimeter has been reconstructed, using wood for the frame- 

 work and "compo" board and cork for the outside insulating walls. 



J For full description, see Benedict and Carpenter, Carnegie Inst. Wash. Pub. 123, 1910, p. 57. 

 Recently the Crowell blower has been adopted with success. 



