3° 



ELEMENTS OF WATER BACTERIOLOGY. 



The following table from Gage and Phelps shows con- 

 clusively the effect of the general composition of the 

 nutrient medium. 



TABLE SHOWING PERCENTAGES OF BACTERIA DEVELOPING ON MEDIA OF 



DIFFERENT COMPOSITIONS. 



(Gage and Phelps, 1902.) 



Medium. 



Days' Count. 



Nahrstoff agar 



Nahrstoff pepton agar. 



Pepton agar 



Meat agar 



Plain agar 



Regular agar 



Nahrstoff glycerin agar 

 Nahrstoff meat agar. . . 



Meat gelatin 



Pepton gelatin 



Standard gelatin 



Plain gelatin 



Nahrstoff gelatin 



100 

 3° 

 24 

 17 

 14 

 11 

 11 

 10 

 26 

 20 

 13 

 J 3 

 13 



Finally, Whipple (Whipple, 1902) has shown that not 

 only the particular kind of gelatin used but its exact 

 physical condition as affected by sterilization and other 

 previous treatments will materially affect the results 

 obtained. It is evident, therefore, that only the strictest 

 adherence to some standard method can ensure com- 

 parable results; the ordinary nutrient gelatin should 

 then in all practical sanitary work be made up in exact 

 accordance with the direction of the A. P. H. A. Commit- 

 tee as given in the Appendix. 



