290 The Influence of Environment 



is not sufficiently long, only part of the colloid coagulates ; 

 in this case an organism may again recover. 



Inside of these upper and lower temperature limits 

 we find that life phenomena are influenced by tempera- 

 ture in such a way that their rate is about doubled for 

 an increase of the temperature of io° C, and that this 

 temperature coefficient for io°, Q I0 , very often steadily 

 diminishes from the lower to the higher temperature; 

 so that near the lower temperature limit it becomes 

 often considerably greater than 2 and near the higher 

 temperature limit it becomes very often less than 2. 1 

 This influence of temperature is so general that we are 

 bound to associate it with an equally general feature of 

 life phenomena; and such a feature would be most 

 likely the chemical reactions. It is known through the 

 work of Berthelot, van't Hoff, and Arrhenius that the 

 temperature coefficient for the velocity of chemical 

 reactions is also generally of about the same order of 

 magnitude; namely ^2 for a difference of io°. In 

 chemical reactions there is also a tendency for Q I0 to 

 become larger for lower temperature, and coefficients 

 of Q I0 about 5 or 6 have repeatedly been found for 

 purely chemical reactions between o° and io°, e. g., 

 for the inversion of cane sugar by the hydrogen ion. 

 The temperature coefficient for the reaction velocity 

 of ferments shows the same diminution of Q I0 with 



1 A full discussion of the literature on temperature coefficients is given 

 in A. Kanitz's book on Temperatur und Lebensvorgdnge, Berlin, 1915. 



