BACTERIOLOGY OF WATER AND MILK 



175 



into seventeen groups each dominated by a certain species. 

 He does not believe it practicable to extend water analyses 

 beyond the identifying of the group in which the organism 

 belongs and the identification of the important and well de- 

 fined species. For these organisms the methods described in 

 this volume are sufficient but for the differentiation of many 

 water bacteria it is necessary to employ special media and 

 methods. The groups into which water bacteria may be di- 

 vided as suggested by Jordan are as follows: 

 Group I B. coli communis. 



Group II B. lactis aerogenes. 

 Group III B. proteus. 

 Group IV B. enteritidis. 

 Group V B. fluorescens liquefaciens. 

 Group VI B. fluorescens non-liquefaciens. 

 Group VII B. subtilis. . 



Group VIII Non-gas forming, non-fluorescent, non-spore- 

 forming bacilli which liquefy gelatin and acidi- 

 fy milk. 

 Group IX Similar to Group VIII, save that the milk is 



rendered alkaline. 

 Group X Similar to Group VIII, save that gelatin is not 



liquefied. 

 Group XI Similar to Group IX, save that gelatin is not 



liquefied. 

 Group XII Similar to Group XI, save that the reaction of 



milk is not altered. 

 Group XIII Chromogenic bacilli not included in the above 



groups. 



Group XIV Chromogenic staphylococci. 

 Group XV Non-chromogenic staphylococci. 

 Group XVI Sarcinac. 

 Group XVII Streptococci. 



Pure water is not a favorable medium for the multiplica- 

 tion of bacteria unless it be those in class I. The individuals 

 of most species die quite rapidly in water. However, a few 

 persist for a long time. 



