44:6 COMPARATIVE PHYSIOLOGY. 



(106 F.); snakes, 10° to 12° (50 to 53-6 F.); but higher in large 

 specimens (python). Cold-blooded animals have a tempera- 

 ture a little higher (less than 1° C. usually) than the surround- 

 ing air. During the swarming of bees the hive temperature 

 may rise from 33° to 40° (89-6 to 104 F.). All cold-blooded 

 animals have probably a higher temperature in the breeding- 

 season. In our domestic mammals the normal temperature is 

 not widely different from that of man. In the horse the aver- 

 age is 37-5° to 38° (99-5 to 100'4 F.) ; in the ass, 38° to 39-5° (100-4 

 to 103 F) ; in the ox, 38° to 38-5° (100-4 to 101-3 F.) ; in the sheep 

 and pig, 39° to 40° (103-2 to 104 F.) ; in the cat, 38-5° to 39° (101-3 

 to 103-3 F.); in the dog, 38-5° (101-3 F.). 



Variations in the average temperature are dependent on 

 numerous causes which may affect either the heat production 

 or heat loss : 1. Change of climate has a very slight but real 

 iniluence, the temperature being elevated a fraction of a degree 

 when an individual travels from the poles toward the equator, 

 and the same may be said of the effect of tlie temperature of a 

 warm summer day as compared with a cold winter one. The 

 wonder is that, considering the external temperature, the vari- 

 ation is so light. 2. Starvation lowers the temperature, and 

 the ingestion of food raises it slightly, the latter increasing, the 

 former decreasing, the rate of the metabolic processes. 3. Age 

 has its influence, the very young and the very old, in whom 

 metabolism (oxidation) is feeble, having a lower temperature. 

 This especially applies to the newly born, both among man- 

 kind and the lower mammals ; and, as might be suppo.sed, the 

 temperature falls during sleep, when all the vital activi- 

 ties are diminished. The same remark applies with greater 

 force to the hibernating state of animals. The temperature 

 of man does not vary more than about 1° C. during tlie twenty- 

 four hours. 



It will be inferred, from the facts and figures already cited, 

 that different kinds of food have considerably different capacity 

 for heat production. 



It is well known that an animal when working not only 

 feels warmer, but actually produces more heat. 



It appears from a multitude of considerations that the body 

 is like a steam-engine, producing heat and doing work ; but it 

 is found that while a very good steam-engine, as a result of the 

 chemical processes going" on within it, converts ^ of the poten- 

 tial energy of its supplies into mechanical work, the other | 



