MECHANISM OF DEATH 377 



XI. DEATH BY STARVATION 

 (a) STARVATION IN WATER 



Death of bacteria by starvation has received con- 

 siderable attention on account of its importance in water 

 bacteriology, and in the self -purification of lakes and 

 rivers. Many data have been accumulated for this 

 reason, but the interpretation is very difficult, and in 

 many cases impossible. One difficulty lies in the fact 

 that bacteria, like all other organisms, will be able to 

 live for a certain time on their reserve substances, with- 

 out any food; death by starvation will start only after 

 these stored food substances are used up. This ''period 

 of no deaths" will vary considerably. Another difficulty 

 is founded in the fact that the change from a culture 

 medium to distilled water, or to a balanced salt solution, 

 might injure or kill many cells for reasons other than 

 starvation, e.g., by plasmolysis, leaching out of impor- 

 tant body substances, change of acidity, change of inter- 

 face tension, traces of toxic compounds in water. 



Theoretically, the order of death from starvation is 

 not logarithmic; there should be a period of no deaths 

 before the cells begin to die. Cohen (1922) calls this 

 the induction period. This initial period of no death 

 or slow death is characterized by an increase of the 

 death rate. 



A large set of data on the death of Bad. coli and Bad, 

 typhosum is given by Hinds (1916). The death rates 

 decreased quite decidedly. Very probably, this was 

 caused by "cold shock.'' 



To show this more clearly, the death rates have been computed for 

 each time interval, averaged, and recomputed on the basis that this 

 average is 100. The result is shown in Table 120, which represents 



