THE TOTAL EXCHANGES OF THE BODY 623 



by electric thermo couples, any difference of temperature being at once 

 compensated by electrically warming the cooler part. The chamber con- 

 tains a bicycle or other arrangement for the performance of mechanical 

 work. It is adequately ventilated by a current of air passing through an 

 apparatus similar to that of Benedict, described on p. 617. It is thus possible 

 to estimate simultaneously the total heat production of an individual as well 

 as the respiratory exchanges, including both carbon dioxide output and 

 oxygen intake. The general principle of the calorimeter is shown in the 

 diagram (Fig. 319). The calorimeter is also supplied with bed, table, 

 chair, &c., and food can be introduced through a double window so that 

 an experiment may be continued over two or three days on one and 

 the same individual. 



