356 PRINCIPLES OF ANIMAL NUTRITION. 
several temperatures, and the same facts are also shown graphically 
in the accompanying diagram. 
Disposed of by 
Temperature Total Heat 
of Air. Production, Conduction As Latent 
Deg. C. Cals. and Heat of Water 
Radiation, Vapor, 
Cals. Cals. 
7.6 83.5 71.7 11.8 
15.0 63.0 49.0 14.0 
20.0 53.5 37.3 16.2 
25.0 54.2 37.3 16.9 
30.0 56.2 30.0 26.2 
LATENT|HEAT OF WATER VAPOR 
RADIATION AND|CONDUCTION 
7.6°C 15°C 20°C 25°C 320°C 
It appears, then, that a certain minimum heat production, 
corresponding to the metabolism at the critical temperature, is 
inseparably connected with the life of the animal. The very fact 
that the heat production at this temperature is a minimum shows 
that its amount is not determined by the needs of the organism for 
heat. If the latter were the controlling condition, a rise of exter- 
nal temperature should still further reduce the generation of heat, 
while as a matter of fact it is accompanied by a slight increase up 
to the point where the amount of heat produced overpasses the 
ability of the organism to dispose of it and death results. The 
natural conclusion is that the metabolism at the critical tem- 
perature is that which is necessary for the performance of the 
various functions of the organism, and that the heat production 
at this temperature, therefore, represents the amount of energy 
necessarily consumed in the internal work of the body. This is, 
of course, Rubner’s conclusion (p. 346) in a slightly altered form. 
The case is not unlike that of a room in which a fire must be 
kept burning for some purpose—a kitchen, for example. In winter, 
changes in external temperature may be met by burning more or 
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