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^o, 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.^ 

 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 10°. In 

 chemical reactions there is also a tendency for Qio to 

 become larger for lower temperature, and coefficients 

 of Qio about 5 or 6 have repeatedly been found for 

 purely chemical reactions between 0° and 10°, 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 Qio with 



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

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



