PHTSIOLOGT 19 



pure sodium chloride. We find that it is at once 

 injured, and if the exposure be sufficiently pro- 

 longed it is killed. During the whole time of ex- 

 posure to the solution of sodium chloride its 

 electrical resistance (measured with an alternat- 

 ing current) falls steadily until the death-point 

 is eventually reached j after this there is no fur- 

 ther change. A study of the time curve of this 

 process shows that it corresponds to a monomo- 

 lecular reaction (slightly inhibited at the start). 

 This may be expressed in the form of an equa- 

 tion which can be utilized to predict the curve of 

 death under various conditions. We find that in 

 testing these predictions we must ascertain when 

 the death process reaches a definite stage (i.e., 

 when it is one-fourth or one-half completed). 

 This can be determined experimentally with a 

 satisfactory degree of accuracy. 



We can therefore follow the process of death 

 in somewhat the same manner that we follow 

 the progress of a chemical reaction in vitro; in 

 both cases we obtain curves which may be sub- 

 jected to mathematical analysis, from which we 

 may draw conclusions regarding the nature of 



