654 ANIMAL HEAT 



stream of water flowing through the chamber in a series of tubes, the 

 temperature within the calorimeter being kept constant by regulating 

 the temperature and velocity of the entering stream of water. The 

 quantity of the escaping water and the increase in its temperature are 

 measured, and the heat production can then be calculated. The 

 apparatus consists of a chamber in which a human being can live for 

 several days and nights. A stream of air is supplied, and the chemical 

 changes produced in this are investigated in the manner already 

 described (p. 239). 



Fig. 211. Respiration Calorimeter (Atwater). Interior of chamber. A corner of 

 the inner copper wall is supposed to be taken away. The ventilating air-current 

 enters the chamber at the lower end of W, and leaves the chamber through the 

 long tube fastened above W. The copper tubes H, H are surrounded by copper 

 discs I, I, fastened on them like a string of beads to increase the surface. These 

 tubes constitute the arrangement through which the stream of water flows which 

 removes the heat formed in the chamber. J, J are copper troughs which receive 

 the water dropping from H, H. M, M, M are electrical thermometers which show 

 the temperature of the chamber; N, N, similar thermometers which show the 

 temperature of the copper wall. 



Air calorimeters have sometimes been used for physiological pur- 

 poses. A diagram of one is shown in Fig. 212. Such calorimeters are 

 really thermometers with an immense radiating surface, for only a 

 small proportion of the heat given off by the animal goes to heat the 

 measuring substance. The heat required to raise the temperature of a 

 litre of air by i is very small in comparison with that required to raise 

 the temperature of a litre of water by the same amount. Hence a given 



