34 HOMOIOTHERMISM 



affected until there is considerable reduction. Tiger- 

 stedt (1906) observed a man who retained consciousness 

 with a temperature of only 26.7 deg. C. and discusses 

 persons who recovered after extreme exposure during 

 which the temperature of the body fell to 24 deg. C. 



An increase of the temperature beyond certain limits 

 involves general disturbances in the health of an organ- 

 ism. In general animals stand a decrease better than an 

 increase in temperature. A rise of only 2 and 3 deg. C. 

 may cause very severe disorders. A temperature of 41 

 or 42 deg. C. in the human body is regarded as a very 

 dangerous symptom if prevailing for more than a short 

 time. 



Constancy of Body Temperature. — While a given in- 

 dividual is said to have a certain body temperature, it 

 should not be assumed that the entire body is at the same 

 temperature; in fact, such is not the case. The differ- 

 ences between various parts of the body may amount to 

 several degrees. This has been notably demonstrated by 

 Bazett (1927) and his co-workers. By means of specially 

 designed thermocouples he has shown that temperature 

 gradients exist in the body, the internal temperatures 

 highest and decreasing toward the exterior. The gradi- 

 ent is greater when the temperature of the environment 

 is lower. 



Homes. — The usual functions of the homes built by 

 animals are as refuges from enemies, often with particu- 

 lar reference to guarding and rearing the young, and as 

 places for storing food. In many cases homes also serve 

 for protection against the elements, a shelter against 

 storms, and an inclosure for protection against the ex- 

 treme temperature changes of the surroundings. Some 

 animals build their homes of vegetation; others burrow 

 beneath the ground beyond the frost line, where they may 



