RESPONSES OF POIKILOTHERMS TO VARIATIONS 21 



with a turtle weighing 278 grams with heat absorbed first 

 by a living turtle and then with the same turtle dead. 



Figure 1 illustrates how blood circulation apparently 

 influences the temperature gradient between the surface 

 of an animal and the surrounding medium. It is also 

 interesting to note that, in consequence of the influence 



\io 



i 6 



A\ \B 



10 



20 



SO 



TIME IN MINUTES 



40 



50 



Fie. 1. — Rate of response to an altered environmental temperature in 

 a living and dead turtle. A — living turtle; B — same turtle dead. 



of temperature on the rate of heart beat and velocity of 

 blood flow, the temperature of the turtle more quickly 

 approaches the temperatures of the water bath at higher 

 temperatures than at lower. If the medium is kept 

 in motion the gradient will be higher than if it is stag- 

 nant. A terrestrial animal will gain or lose heat 

 more rapidly if it is exposed to convectional cur- 



