316 



PHYSIOLOGICAL REGULATIONS 



At very low body temperatures and loads, it was observed, the 

 rates of all beat exchanges are absolutely slower than at interme- 

 diate ones. This may possibly represent a zone of loads extremely 

 embarrassing to the narcotized organism; indeed, in slightly dif- 

 ferent circumstances recovery might not occur. 



The development of heat equilibration during infancy may also 

 be viewed in the rabbit (fig. 151). It seems to me that the signifi- 

 cance of equilibration is best appreciated by comparison of the 

 usual organism with an organism partially divested of regulations. 

 8 



c 

 o 



a 



0) 



X 



s- 

 o 



o 



DC 



6- 



4- 



2 - 



°6 



-4-2 +2 



Heat Load-Cal./kg. 



+4 



Fig. 150. Eate of net heat exchange in relation to heat load in several species of 

 vertebrates. Comparison of net heat equilibration diagrams. Man, A, data taken from 

 figure 144, and B, data from figure 146; Eabbit, data from figure 149; Mouse, Snake 

 (Boa) and Lizard (Heloderma) , data from figure 152. 



Such is the infant. The gradual acquirement of the compensatory 

 responses to load then outlines in a vivid manner what the stabili- 

 zation means in the life of the individual. The high rate of heat 

 production of the newborn animal is not greatly increased in heat 

 deficits (Giaja, '25b). Shivering develops at about 4 days after 

 birth (Ginglinger and Kayser, '29). Before that age, recovery 

 appears to depend on the automatic decrease of heat losses in a 

 suitable environment, selected by the parent or by the experi- 

 menter, rather than upon any great modification of functions in 

 the body. 



Older individuals economize on energy turnover, and with it 



