RATE OF THE HEART-BEAT IN A CRUSTACEAN. 247 



EXPERIMENT 10. 



Temperature. Beats per Second. 

 29 6.15 



21 3.06 



21 3.23 



19 2.86 



Rate at 29 



Rate~at 7g = 



The beat was regular throughout, but the temperature had 

 been raised above 29 before the observations at 21 were taken. 



EXPERIMENT n. 



Temperature. Beats per Second. 



17 2-38 



21 4.04 



27 5 



Rate at 27 

 Rate at 17 = 



The observations were taken in the following order, 21, 17, 



27. 



EXPERIMENT 12. 



Temperature. Beats per Second. 



13 2.28 



21 4-57 



23 5 



Rate at 23 

 Rate at 13 = 



Rate at T 



5. The average value of the coefficient -^- ".t 10 for all the 



Rate at f n 



observations made was 2.03. The results are therefore such as 

 to confirm Snyder's observations, referred to above, in so far as 

 they apply in general to rhythmically contracting tissues and to 

 lead us to conclude that a chemical reaction is involved --as I 

 have assumed in previous papers. 1 



6. The rate of the beat in different individuals at 21 is 

 remarkably constant, provided they have been treated in the 

 same manner and have not been subjected to any extreme tem- 

 peratures this is particularly well shown in experiments 7 and 



1 Transactions of the Royal Society of South Australia, Vol. XXIX., p. 47; 

 Plilger' 1 s Arch. f. d. ges. Physiologie, Bd. IIO, s. 610. 



