NORMAL PROCESSES OF ENERGY METABOLISM 575 



permitting very little opportunity for radiation or conduction of heat from 

 the inside out or from the outside in. For additional security against 

 the radiation of heat from the calorimeters the original device of Rosa is 

 repeated in all of these calorimeters. This is based upon the ability to 

 hold the temperature of the zinc wall at the same level as that of the cop- 

 per wall. To this end it is necessary to know first that there is a tempera- 

 ture difference between the zinc and copper and second to have some method 



Fig. 26. The Sage calorimeter at BcLlevue Hospital, New York City. The ab- 

 sorber table is shown at the extreme left, the observer's table in the middle and the 

 respiration chamber at the right. Air is circulated by a blower, shown on the lower 

 shelf of the absorber table, through overhead pipes which may be seen entering the 

 calorimeter at the upper left hand corner. Oxygen is admitted from a cylinder shown 

 on the extreme right. 



for controlling the temperature of the former. The temperature differences 

 of the two walls are recorded by means of electrical thermo-j unctions, sepa- 

 rate series of which are arranged in the sides, in the top and in the bot- 

 tom of the apparatus (the ends of several thermal junctions can be seen 

 in Fig. 20). A current flowing through these thermal junctions is read 

 on a Wheatstone bridge at the observer's table and fluctuations of tempera- 

 ture between the two walls alters the amount of this current. To insure 

 a cooling effect on the zinc wall a coil of copper tubes carries a thin cur- 

 rent of water and to counteract this cooling effect a wire running in the 

 same space and between the cooling pipes is heated by sending through it 

 the desired amount of current. Adjustable rheostats are within reach of 



