286 MICRO-ORGANISMS IN WATER 



CHAPTER VIII 



THE VITALITY OF PARTICULAR PATHOGENIC BACTERIA 

 IN DIFFERENT WATERS 



The difficulties which, in the last chapter, we have seen 

 attend what may be called the analytical method of 

 investigation into the fate of pathogenic bacteria gain- 

 ing access to natural waters, early led to supplementary 

 researches by what may be called the synthetic method, 

 in which the pathogenic organisms were purposely in- 

 troduced on an experimental scale into different kinds 

 of water, which were then kept under observation and 

 examined from time to time for the bacteria in ques- 

 tion. 



Although at first sight it might appear an easy task 

 to thus synthetically determine the vitality of organisms 

 in water, requiring only their introduction into various 

 waters and the subsequent estimation of their numbers 

 at suitable intervals of time, as a matter of fact, how- 

 ever, the number of problems requiring solution in this 

 connection is continually increasing ; for as our know- 

 ledge of the physiology and morphology of bacteria 

 becomes more extended from day to day, new factors 

 arise which have to be reckoned with in these investi- 

 gations. 



In a subsequent chapter we shall refer to the action 

 of light on micro-organisms. Whilst we have already 

 learnt how great is the effect of temperature upon the 



