TEMPERATURE AND AUTONOMOUS RESPONSES 333 



32 minutes, or nearly to two-thirds of the period at 19 C. 

 At 28 C. it was found to be again reduced to 21 minutes, 

 or half. But at 40 C. it 

 was only 1*4 minute, or 

 one-third. Thus, while 

 in 4-3 minutes, at 19 C. 

 there is only a single 

 beat, there are two beats 

 at 2 8° C. and three beats 

 at 40 C. in the same 

 time. I give below (fig. 

 138) a record of these 

 responses at various 

 temperatures. The re- 

 cord given afterwards 

 (fig- r 39) shows how 

 similar is the effect of 

 temperature on the 

 amplitude and rhythm 

 of the pulsation of the 

 animal heart. When 

 the temperature of Desmodium is raised above 40 C. there 

 appears to be an arrest of pulsation. But this need not be 



Fig. 136. Effect of Lowering of Tempera- 

 ture in Producing Increase of Amplitude 

 and Decrease of Frequency in Pulsation 

 of Frog's Heart 



The pulsations to the left represent normal 

 pulsations at the temperature of the 

 room. Those to the right were taken 

 at a temperature several degrees lower 

 (after Brodie). 



Fig. 137. Photographic Record of Pulsations of Desmodium during 

 Continuous Rise of Temperature 



regarded as due to heat-rigor. For in magnified records 

 I have often noticed that here we may have very much 



