Quantitative Bacteriological Examination. 39 



deviation either way decreased the number of colonies 

 developing. 



TABLE SHOWING PERCENTAGES OF BACTERIA DEVEL- 

 OPING ON MEDIA OF DIFFERENT COMPOSITIONS. 



(GAGE AND PHELPS, 1902.) 



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

 particular kind of gelatin used but its exact physical con- 

 dition as affected by sterilization 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: 



