No. 582] SIGNIFICANCE OF INTERNAL CONDITIONS 351 



Further details should be sought in the text-books of 

 physical chemistry, and especially those by Bancroft and 

 Findlay on the phase rule. 40 



IV. The Interpretation of the Regulatory Mechan- 

 isms in Terms of Chemical Equilibrium 

 But what evidence is there that the laws of mass action 

 or of chemical equilibrium apply to living matter? Is 

 there any evidence that the reactions occurring in the 

 cell are "slow" reactions similar to those of the physico- 

 chemical laboratory ! The answer to these questions is 

 decidedly in the affirmative. Much evidence in favor of 

 such a view was presented by Blackmail. Hofmeister, 

 Bredig and others regard the cell as a congeries of en- 

 zymes, each one, according to Hofmeister, 41 acting in its 

 own compartment upon its own peculiar substrate. 



1. Applications of Van't Hoff's Law 

 As further evidence of the nature of the reactions in 

 living matter, we may cite the work of Shelford 42 on tiger 

 beetles, in which the length of the combined quiescent 

 periods of the pupal and the prepupal stages was in- 

 creased from four or six weeks at a temperature of 28° 

 to 30° C. to ten or twelve weeks at a temperature of 15° 

 to 17° C. Riddle 43 found that the temperature coeffi- 

 cients for digestion in Amia, Rana, Necturus and the 

 common turtle {Emydoidea) ranged from 0.93 in Nec- 

 turus to 7.81 in the turtle. Rogers and Lewis 44 have re- 

 cently shown that the temperature coefficient of the rate 

 of contraction of the dorsal blood vessel of the earthworm 

 is of the order of magnitude to be expected if the processes 



*o Bancroft, "The Phase Bule," Ithaca, New York; Findlay, "The Phase 

 Bule and Its Applications, ' ' 3d ed., 1911, London and New York. 

 " Hofmeister, loc. ext. 



"Shelford, Linnean Society-* Journal , 190s, XXX, p. 176. 

 "Riddle, American Journal of Physiolo,,,,, 1009. XXIV. pp. 447-458. 

 "Rogers and Lewis, Biological Bulk tin. 1914, XXVII. p. 269. See also 

 Lehenbauer, "Physiological Researches," 1914, I, pp. 247-288. 



