20 CALORIMETERS FOR STUDYING RESPIRATORY EXCHANGE, ETC. 



the junctions is much less. The two lead-wires of German silver can be 

 carried through the end of the spool and thus allow the insulation to be 

 made much more satisfactorily. In these calorimeters free use of these 

 thermal junctions has been made. In the chair calorimeter there are on 

 the top 16 elements consisting of four junctions each, on the rear 18, on 

 the front 8, and on the bottom 13. The distribution of the elements is 

 made with due reference to the direction in which the heat is most directly 

 radiated and conducted from the surface of the body. 



While the original iron-German-silver junctions have been retained in 

 two of these calorimeters for the practical reason that a large number of 

 these elements had been constructed beforehand, we believe it will be more 

 advantageous to use the copper-constantin couple, which has a thermo- 

 electric force of 40 microvolts per degree as against the 25 of the iron- 

 German-silver couple. It is planned to install the copper-constantin junc- 

 tions in the calorimeters now building. 



INTERIOR OF THE CALORIMETER. 



Since the experiments to be made with this chamber will rarely exceed 

 6 to 8 hours, there is no provision made for installing a cot bed or other 

 conveniences which would be necessary for experiments of long duration. 

 Aside from the arm-chair with the foot -rest suspended from the balance, 

 there is practically no furniture inside of the chamber, and a shelf or two, 

 usually attached to the chair, to support bottles for urine and drinking- 

 water bottles, completes the furniture equipment. The construction of the 

 calorimeter is such as to minimize the volume of air surrounding the subject 

 and yet secure sufficient freedom of movement to have him comfortable. 

 A general impression of the arrangement of the pipes, chair, telephone, etc., 

 inside the chamber can be obtained from figs. 7 and 9. The heat-absorber 

 system is attached to rings soldered to the ceiling at different points. The 

 incoming air-pipe is carried to the top of the central dome, while the air is 

 drawn from the calorimeter at a point at the lower front near the position 

 of the feet of the subject. From this point it is carried through a pipe along 

 the floor and up the rear wall of the calorimeter to the exit. 



With the perfect heat insulation obtaining, the heat production of the 

 man would soon raise the temperature to an uncomfortable degree were 

 there no provisions for withdrawing it. It is therefore necessary to cool 

 the chamber and, as has been pointed out, the cooling is accomplished by 

 passing a current of cold water through a heat-absorbing apparatus per- 

 manently installed in the interior of the chamber. The heat-absorber con- 

 sists of a continuous copper pipe of 6 millimeters internal diameter and 10 

 millimeters external diameter. Along this pipe there are soldered a large 

 number of copper disks 5 centimeters in diameter at a distance of 5 milli- 

 meters from each other. This increases enormously the area for the absorp- 



