198 MAX KLEIBER 



9. Partitional Calorimetry and Kata Thermometer 



For characterizing the thermostatic behavior of animals a parti- 

 tion of the total heat flow into its components — radiation, convection, 

 and evaporation of water — is important. Rubner has already worked 

 intensively on this problem and has found that for average comfort- 

 able conditions evaporation accounted for about 20% of the total heat 

 loss, convection and conduction for 30%, and radiation for 50%. 

 Such measurements have been extended and refined, especially by 

 Hardy and Dubois and by a group of biophysicists at Yale University 

 (30). 



Hardy (13) has designed a radiometer that measures radiant en- 

 ergy after its conversion to heat at a black surface. One thermo- 

 electric junction is installed on the blackened receiver of radiation 

 and the other junction of the electric thermocouple is at a point 

 shielded from the radiation. The difference in temperature, indi- 

 cated by the electric potential between the two junctions, measures 

 the intensity of radiation. On the basis of Stefan-Boltzmann's law 

 of radiation, the radiometer may be used also to measure surface tem- 

 peratures of animals. 



The Hardy radiometer measures the surface temperature of ani- 

 mals in comparison with the temperature of a reference body. If 

 this reference body is at the temperature of the entire environment 

 such as the walls, floor, and ceiling of a room, the heat radiated from 

 a square centimeter of the animal surface may be calculated on the 

 basis of the Stefan-Boltzmann law : 



AQ^/A At = a(n - T'r) (18) 



where AQr/A At = rate of heat loss by radiation per square centi- 

 meter of surface area, a — Stefan-Boltzmann constant = 1.37 X 

 10~^2 cal. per second per square centimeter, Tg = temperature of 

 radiating surface, in degrees absolute, and T^ — temperature of re- 

 ceiving surface, in degrees absolute. 



In the John Pierce Laboratory at Yale, radiation may be con- 

 trolled by surrounding the experimental person with copper sheets 

 that reflect radiant heat received from outside. The temperature of 

 the walls in radiation exchange with the body may thus be varied in- 

 dependently of the temperature of the air surrounding the body. 



The reverse tendency to the differentiation of the total heat loss 

 of animals into the various paths is the integration of the thermal 

 environmental factors into one figure. This integration is accom- 



