106 LIFE: ITS NATURE AND ORIGIN 



For protection against cold, warm-blooded animals have hair, 

 fur, feathers, or layers of fat (whale). When we get "blue with the 

 cold," our blood has stagnated to reduce heat loss; and shivering, 

 probably initiated by the hypothalamus, represents involuntary 

 "exercise." As protection against heat, animals seek shade, but 

 rely mainly upon radiation of heat to the air, which may be aided 

 by perspiration, since water has a high latent heat of vaporization. 

 Dogs, which have no sweat glands, loll out their tongues, and I 

 have seen sparrows near Merced, Cal., in the meager shade of 

 fence posts, "panting" to endure a temperature which registered 

 over 110° F in the shade above ground level. 



Efficiency in Biocatalysis 



The ideal heat-engine of Carnot (1824) has a theoretical effi- 

 ciency of about 50 per cent. For steam engines, it is about 20 per 

 cent, for gas engines about 25 per cent, for diesel engines about 

 40 per cent; but actual results may go considerably below these 

 figures. A standard cadmium storage "battery" or cell, slowly 

 charged and discharged, may approach 100 per cent efficiency; and 

 it is to be expected that animals, operating likewise by chemical 

 energy rather than by differences of temperature, will show high 

 efficiency — and they do. But the situation is greatly complicated 

 by the fact that animals utilize much of the energy of their food 

 in mere maintenance and in growth and reproduction, which 

 involve synthetic processes which require heat. The efficiency of 

 some of these synthetic processes may be low, but the "waste" heat 

 may be utilized in speeding up or initiating other chemical 

 changes, as well as in keeping up the body temperature when dis- 

 tributed by the blood. 



The efficiency of autotrophic bacteria in producing ammonia from 

 atmospheric nitrogen approximates 3 per cent, 16 while that Nitro- 

 bacter, using the energy derived from oxidation of nitrite to nitrate, 

 to assimilate carbon from carbon dioxide, is reported as about 6 per 

 cent. 17 O. Rahn 18 estimates that one Calorie value in food produces 

 the following heat liberation (in Calories) in various animals: pig, 

 0.2-0.4; trout, 0.18-0.31; cockroach, 0.34-0.35; mold, 0.58-0.70; colon 

 bacillus, 0.13-0.24; pseudomonades, 0.21-0.22. Agriculturists estimate 

 efficiency in terms of useful or marketable products produced — wool, 

 meat, hide or skin, fat, eggs, milk, manure, etc. 



By directing the course of chemical reactions with restricted 

 heat emission, at localized areas and at regulated velocities, cata- 



