WHITE AND ORANGE STAPHYLOCOCCI 



155 



considerable proportion of strains that fail to do so if the compo- 

 sition of the medium is not altogether favorable. 



The distribution of results in broth containing maltose, sucrose 

 or lactose is generally similar except that the differential effect of 

 the peptone broth seems to be less marked in the case of maltose 

 and lactose. 



Throughout all the tests, however, the dehydrated broth is 

 characterized by a higher acidity than the peptone medium. 



The proportion of acid, neutral and alkaline reactions for each 

 of the carbohydrates studied is indicated in the table above. 

 Raffinose, mannitol, dulcitol, salicin and inulin were studied only 

 in the peptone medium. 



It may be of interest to compare with the results presented 

 in table 3 the data obtained by Dudgeon (1908) using the change 

 in the color of litmus as the sole measure of acid production. We 

 have calculated the percentage of positive results obtained by 

 him for his two chief groups of 46 orange strains and 71 white 

 strains in table 4. 



Glucose, maltose, sucrose and lactose appear most readily fer- 

 mentable in either case, but the use of litmus (which is a highly 

 inaccurate indicator), with no study of the progressive change in 

 reaction, led Dudgeon to report a large number of positive results 



