THE EFFECTS OF HEAT AND RADIANT ENERGY 109 



the reaction area between enzyme and fermentable substance is 

 diminished. The question arises, Can we show that certain life phe- 

 nomena are a direct function of a reaction velocity? In my book on 

 the Comparative Physiology of the Brain, I expressed the idea that 

 the rhythmical contractions of the jellyfish, of the heart, and perhaps 

 in general, are a function of enzymatic processes. It seemed to me 

 that this idea could be put to a test, since in case it were true, the 

 rate of heartbeats should vary with the temperature, according to the 

 figures found by Arrhenius for the influence of temperature, upon re- 

 action velocity, i.e. we should find that with a rise of temperature of 

 10 C. the rate of heartbeats should at least double. At my request 

 Mr. Snyder undertook experiments in this direction on strips of the 

 ventricle of the tortoise heart. He found, indeed, that inside the tem- 

 perature range of from 5 to 30 C., the number of heartbeats is about 

 doubled for every rise of temperature of 10 C. The strips of the ven- 

 tricle were kept in a moist chamber, which was submerged in a water 

 bath of constant temperature. The contractions of the strips were 

 recorded in the usual way. I will give as an example the records of 

 six experiments.* The hearts of six terrapins were put into moist 

 chambers, and the latter were kept at a constant temperature for two 

 hours and forty minutes. Two strips were kept at a temperature of 

 10 C., two at 20 and two at 30. The average number of heartbeats 

 was determined for every five or ten minutes. The left vertical column 

 of the following table gives the time in minutes, the other vertical 

 columns gives the average number of heartbeats for each heart at that 

 time. 



TIME r=io r=2o r=so 



MINUTES HEART i HEART 2 HEART 3 HEART 4 HEART 5 HEART 6 



5 9.5 9.5 21.5 21 48 48 



10 79 21 24 48 44 



15 6.7 8.7 19 18 48 40 



20 7 8.2 19 16.5 41 



30 77 16 14 



40 6.5 7.9 15.5 15-5 



50 6.5 7.9 13-5 l6 



60 6.2 7.4 13 15 



80 6.2 6.8 ii 14.5 



100 6.5 7.1 10 10 



120 6.4 6.6 10 



140 6.5 6 89 



160 6.5 5.9 7.6 9 



Other experiments gave similar results. The experiments show that 

 the influence of temperature upon the rate of contractions in different 



* C. D. Snyder, University of California Publications, Physiology, Vol. 2, p. 125, 1905. 



