1 6 A RESPIRATION CALORIMETER. 



one about 96 mm. above the other. Two brass pipes, 40 mm. internal 

 diameter, 1 70 mm. long, are screwed into these shoulders. To provide 

 for slight differences in the exact position of the chamber when it is 

 withdrawn and again put in place in the wooden house, it was found 

 desirable to have the final coupling with the outside air-pipes more or 

 less flexible, and consequently the coupling was attached to the brass 

 pipes screwed into the wall by short lengths of thick- walled rubber 

 tubing. A small wooden box with openings for the two pipes was 

 attached by wax and small nails to the zinc wall of the chamber and 

 wooden upright between the zinc and copper walls. The box was so 

 adjusted that it held the flexible couplings in the proper position for 

 satisfactory connection to the outer air-pipes. Plaster of Paris was 

 poured into the top of the box and the whole mass allowed to set ; 

 this serves as an excellent support for the pipes, and yet the flexibility 

 of the rubber allows considerable twisting motion in making the 

 connections. When the chamber is put in place in the house the 

 rectangular box supporting the air-pipes fits perfectly into an opening 

 through the two front panels, shown to the left of the window open- 

 ing in figure 31. The box is sufficiently long to project clear through 

 both wooden walls and thus allow the making of an easy connection 

 with the air-pipes outside. With this arrangement there can be no 

 leakage through the air-pipes or through the joint between the air-pipe 

 and the inner copper wall. 



Opening for weighing apparatus. In order to permit of accurate 

 weighing of the subject inside the respiration chamber, the weighing 

 apparatus shown in figure 46 is situated on the floor of the room 

 above the chamber and a metal rod connects the scales with the chair 

 upon which the subject sits ; consequently an opening through the 

 top of the chamber is necessary to allow the passage of this rod. This 

 opening is 35 mm. in diameter, and consists of a hard rubber tube 

 tightly screwed into a metal flange soldered to the top of the copper 

 wall. When the weighing apparatus is not in actual use the opening 

 is closed by a tightly fitting rubber stopper. A number of tests have 

 shown that this closure can be made uniformly without leak. 



Opening for the water-pipes. As is described in detail beyond, a water 

 current is used to bring away the heat generated by the subject. The 

 passage of this current through the metal walls was secured by solder- 

 ing to the opening in the walls a stiff metal ring, as in the case of the 

 food aperture. A round wooden plug, previously well boiled with par- 

 affin to render it non-porous and so prevent gain or loss of water, was 

 then driven firmly into this ring and tightly sealed by means of wax. 

 The plug is shown in position in figure 30 immediately at the right and 



