NOTE ON THE INFLUENCE OF TEMPERATURE 



UPON THE RATE OF THE HEART-BEAT IN 



A CRUSTACEAN (CERIODAPHNIA). 1 



T. BRAILSFORD ROBERTSON. 



1. Arrhenius has shown 2 that the velocity of a chemical 

 reaction increases very much more rapidly with increasing tem- 

 perature than any known physical phenomenon. The velocity 

 of a chemical reaction increases about 10 per cent, per degree 

 centigrade rise in temperature while molecular velocity, the elec- 

 tric conductivity of a wire, the elasticity of a solid, the viscosity 

 of a fluid, surface-tension, etc., are much less affected by the same 

 rise of temperature. The viscosity of a fluid, for example, only 

 diminishes about 2 per cent, per degree centigrade rise in tem- 

 perature. The viscosity of a gas, according to Maxwell's equa- 

 tion for air 3 should increase about 6.7 per cent, per degree centi- 

 grade rise in temperature at 15 C. 



2. The fact of the extreme variability of chemical reactions with 

 temperature has been applied to ascertain whether given biological 

 phenomena involve chemical reactions or not. Arrhenius 4 and 

 van t'Hoff 5 have shown that the quotient 



velocity of reaction at T n+lo 

 velocity of reaction at T n 



is equal to about 2, T n being the absolute temperature. That is 

 to say, the velocity of a chemical reaction increases about 100 

 per cent, per ten degrees. Hertwig 6 has found that the rate of 

 development of frog's eggs increases very rapidly with rise of 

 temperature. At Dr. Loeb's suggestion C. D. Snyder" investi- 



1 From the Rudolph Spreckels Physiological Laboratory of the University of 

 California. 



2 Zeitsch rift f. Physik-Chemie, 1899, Bd. 4, s. 226. 



3 "Theory of Heat," 1872, p. 279. 

 Loc. cit. 



5 " Etudes de dynamique chimique," p. 112, etc. 



6 " Die Zelle und die Gewebe," Bd. II., S. 119. 



7 University of California Publications, Physiology, Vol. 2, p. 125. 



242 



