UPON ENZYMES AND LIVING CELLS 95 



planation of the existence of an optimum temperature of action 

 for all ferments. 



The, temperature coefficient, that is, the variation in the velocity 

 constant with the temperature, which is usually expressed for 

 each 10 C., has been measured by Bayliss in the case of trypsin. 

 It was found that it required 5*3 times as long to effect an equal 

 change at 2O7 C. as at 3O7 C. ; between 3O7 C. and 38'7 C. the 

 ratio of velocities was 2'6 : 1, giving 3*3 as the coefficient for an 

 interval of 10 C. ; also a determination of the velocity at C. 

 gave a coefficient for each 10 interval between C. and 30 C. 

 of 12. In the case of emulsin, between 60 and 70, Tammann found 

 for the temperature coefficient the value of 7*14; Senter for the 

 peroxidase of blood the value of 1*5, between C. and 10 C. 

 (Quoted from Bayliss loc. cit.) 



The living cell in its reaction to temperature changes, in so 

 far as it is not controlled in the higher animals by the temperature 

 regulating mechanism, obeys exactly the same laws as the enzyme. 

 Its activity is only possible, as in the case of the enzyme, between 

 certain well-defined limits, which vary from cell to cell, as from 

 enzyme to enzyme, and somewhere in the range there is an 

 optimum point of maximum activity which is variable under like 

 conditions as in the case of the enzyme. Also at the point of 

 maximum activity, the living cell is working above its safety 

 point, and prolonged action at this point leads to a break-down 

 in the cell's activity, and to death. 



There is an apparent exception in the case of warm-blooded 

 animals in the fact that a slight fall in temperature leads to 

 increased activity, but this is merely due to the action of one 

 cell upon another, to stimulation by the nervous system ; and 

 when on account of continued fall in temperature the regulatory 

 mechanism is overcome, the cells of the warm-blooded : animal 

 obey the general law just as do those of cold-blooded animals. 



On account of the regulatory mechanism, as a result of the 

 action of which the cells of the warm-blooded animals are rarely 

 exposed to any appreciable variations in temperature, the cells 

 have lost their power to respond to temperature variations through- 

 out so wide a range, the minimum and maximum points are close 

 together, and so arises the great danger of temperature variations 

 after the regulating mechanism has been overpowered by greater 

 than normal variations in temperature of external surroundings. 



