44 PROTOPLASMIC ACTION AND NERVOUS ACTION 



physiological range (5°-40°) a rise of temperature of 

 io° more than doubles the rate of most chemical reactions 

 (Qio 2-3); this rule applies to many processes which, 

 though occurring within the living system, have in them 

 nothing that is specifically vital; thus the rate of hydrol- 

 ysis in the digestive tract, the rate of consumption of 

 oxygen or evolution of CO2 by living cells, and the rate 

 of autolysis in dead cells are all accelerated to about 

 the same degree by a given rise of temperature; the 

 same is true of chemical reactions in non-living systems; 

 e.g., the hydrolysis of sucrose by acid. Such accelera- 

 tions are not instances of stimulation in the physiological 

 sense; true stimulation is illustrated only when the 

 organism, cell, or other living system makes a response 

 whose characteristics can be explained only by reference 

 to the special peculiarities of the system as living. 

 Thus a muscle can be mechanically subdivided by 

 scissors, and the purely mechanical action is the same in 

 the living as in the dead muscle; but, in addition, the 

 former contracts, i.e., exhibits its characteristically vital 

 response. Or a living unfertilized starfish egg or frog's 

 egg mechanically treated in an appropriate way begins 

 a sequence of cell-divisions; the same result follows 

 when a starfish egg is kept at 35° for 2 minutes, or treated 



with — butyric acid solution for a similar period. 

 200 



The change in the behavior of the living system under 



a given stimulating condition is normally a constant one, 



but the special nature of this change is determined by 



the specific organization or "inherited" character of 



the system, as well as by its physiological state at the 



time. Hence the same change of conditions acting as a 



