INFLUENCE OF TEMPERATURE UPON LIFE-PROCESSES 419 



the acceleration of hydrolysis is the predominant result of raising the 

 temperature, but at higher temperatures, destruction of the enzyme 

 becomes the controlling factor. The temperature-coefficient for 

 enzyme destruction is exceptionally high, so that the rate of auto- 

 destruction may be imperceptible between 30 and 40 and extremely 

 rapid at temperatures lying between 40 and 50. 



Even in a single uncomplicated chemical transformation the tem- 

 perature-coefficient is not constant, for, reverting to the equation: 



ko 



we see that the temperature-coefficient for 10 temperature-interval 

 is given by: 



i n(-M-\ ' 



KI = e ^VTi T ) 



k 



it is therefore not independent of the absolute magnitude of the tem- 

 perature employed; in fact the temperature-coefficient must invariably 

 decrease as the temperature rises. Assuming a value of /z ( = 13, 200) 

 which would yield a coefficient of 2 between the temperatures of 30 

 and 40, the following table shows the coefficients which might be 

 anticipated at other temperatures : 



Temperature- 



Temperature interval. coefficient. 



0to 10 ................. 2.34 



10 to 20 ................. 2.22 



20 to 30 ................. 2.11 



30 to 40 ................. 2.00 



40 to 50 . . ... ...... ...... 1-92 



The reduction of the coefficient for enzyme reactions at temperatures 

 above 40 is, however, much more extreme than could be accounted for 

 in this fashion, the coefficient ultimately falling to zero at the thermal 

 limit for the activity of the enzyme. 



The actual phenomena of life are almost invariably of a mixed 

 character, involving physical as well as chemical processes and changes, 

 and we may inquire through the investigation of their temperature- 

 coefficients whether the physical or the chemical factors predominate 

 in determining the rate of performance; whether the chemical trans- 

 formations, in other words, are consequent upon preceding physical 

 changes or whether, on the contrary, the physical modifications of 

 protoplasm await and are the resultant of the chemical transformations 

 which accompany the performance of vital activities. 



The first investigator to apply this criterion to the study of life- 

 phenomena was Cohen, who in 1892 pointed out that the previous 



