668 TEMPERATURE AND LATENT PERIOD 



of van't Hoff. The deviations above the optimum temperature are 

 generally dismissed by attributing them to the destructive effect of 

 heat on protoplasm. 



As has been pointed out (Snyder, 1911), the lack of constancy of the 

 temperature coefificient is no bar to a process being chemical in nature. 

 This is simply because purely chemical reactions also fail to show a 

 constant temperature coefhcient. The emphasis is to be placed on 

 the order of magnitude of the coefficient and not on its invariability. 



The real difficulty, however, is that biological phenomena do not 

 represent single chemical reactions. In order, therefore, that the 

 variations shown by biological activities be properly understood, it is 

 necessary to know the nature and number of the chemical reactions 

 concerned, and also their interrelations. Osterhout (1917) has in- 

 deed emphasized this by assuming a wholly imaginary biological 

 activity composed of two consecutive chemical reactions, and syn- 

 thesizing the effect of temperature on their combined activity. An 

 analysis of data actually secured in the study of a vital process has 

 apparently never been made in any but the most approximate man- 

 ner. This is especially true of the variations exhibited by vital proc- 

 esses at higher temperatures. 



Aside from the work of Blackman (1905), so vigorously criticized 

 by Kanitz (1915, p. 22), the one significant contribution in this di- 

 rection has been made by Putter (1914). In the effect of temperature 

 on the oxygen consumption of the leech, Putter attributes the usual 

 variations at higher temperatures to an increasing effect of an inter- 

 fering process. For the estimation of this second factor, Putter 

 compares his actual results with those calculated on the basis of a con- 

 stant temperature coefficient. The difference between the two is then 

 shown to possess an approximately constant temperature coefficient 

 of its own. 



Putter's idea, though correct in general conception, does not yield 

 a quantitatively correct analysis. One reason for this is, as he 

 realizes himself, that his data are not comparable at different tem- 

 peratures; he measures the amount of oxygen consumed in a given 

 time instead of the time for the consumption of a given amount of 

 oxygen. In addition, we are wholly ignorant of the chemical and 

 physical reactions involved in the process. Without such knowl- 



