56 INFLUENCE OF TEMPERATURE 



castor-beans, or of yolk of egg by pancreatic juice. 

 We may therefore say that the vital processes are 

 in this special case very similar to processes in 

 general chemistry. 



It has often been said that there is a great 

 difference between vital and ordinary chemical pro- 

 cesses with respect to the influence of temperature 

 upon them. It is a very common feature that vital 

 and even enzymatic processes show an optimum of 

 temperature. For instance, the assimilation process 

 in plants goes on with a maximum velocity at about 

 37 C., as is indicated by the investigations of 

 Miss GABRIELLE MATTHAEI (see Fig. 12 a). A very 

 similar thing holds good for the inversion of cane- 

 sugar by invertase, according to KJELDAHL (Fig. 

 1 2 d], and the coagulation of milk by rennet, accord- 

 ing to FULD'S experiments (Fig. 126}. The ex- 

 planation of this fact is in reality very simple. The 

 spontaneous destruction of, e.g., the saponifying lipase 

 in castor-beans has a value of //,= 26,000, which is 

 much greater than the corresponding value 7540 

 for the saponification of cotton oil by means of 

 this lipase (according to NICLOUX'S measurements). 

 Therefore at sufficiently high temperatures the 

 enzyme is destroyed during the preliminary heating 

 to this temperature before it is able to exert a 

 sensible action on cotton oil. Hence a maximum 

 effect of the lipase must occur at a temperature 

 below that given. 



Further, the velocity of reaction must in this 

 special case decrease with time ; at very low 



