Quantitative Bacteriological Examination. 39 



deviation either way decreased the number of colonies 

 developing. 



TABLS SHOWING PERCENTAGES OF BACTERIA DEVEL- 

 OPING ON MEDIA OF DIFFERENT COMPOSITIONS. 

 (GAGE AND PHELPS, 1902.) 



Days' Count. 



NahrstoflF agar . . . 

 Nahrstoff pepton agar 

 Peptonagar .... 



Meat agar 



Plain agar . . . 

 Regular agar .... 

 Nahrstoff glycerin agar 

 Nahrstoff meat agar . 

 Meat gelatin .... 

 Pepton gelatin .... 

 Standard gelatin . 

 Plain gelatin . . . 

 Nahrstoff gelatin 



100 



30 

 24 



17 

 14 

 II 

 II 

 10 

 26 

 20 

 13 

 13 

 13 



Whipple (Whipple, 1902) has shown that not only the 

 particular kind of gelatin used but its exact physical con- 

 dition as affected by sterihzation and other previous 

 treatment will materially affect the results obtained. 

 Gage and Adams (1904) found marked differences in 

 counts as the result of the use of the two best known com- 

 mercial peptones. A long series of waters plated on agar 

 made up with Merck's and Witte's peptones, respectively, 

 showed the following average relative results : 



