SUBFAMILIES AND GENERA OF COCCACE^ 95 



In our series of cultures, there was a suggestive corre- 

 lation between acid production and reaction to the Gram 

 stain, the most actively fermenting forms being usually 

 Gram-positive. 



It is evident that the streptococci as a whole constitute 

 an acid-forming, Gram-positive type; and these charac- 

 ters, with the general failure to attack gelatin and nitrates, 

 may, therefore, be included in the characterization of the 

 genus Streptococcus, in addition to its familiar morpho- 

 logical and cultural characters. 



GENUS III. STREPTOCOCCUS (Billroth) Winslow and 

 Rogers. Parasites. Cells normally in short or long chains 

 (under unfavorable cultural conditions, sometimes in pairs 

 and small groups, never in large packets). Generally stain 

 by Gram. On agar streak, effused translucent growth, 

 often with isolated colonies. In stab culture, little surface 

 growth. Sugars fermented with formation of large amount 

 of acid. Generally fail to liquefy gelatin or reduce nitrates. 



There remain to be considered the four color-types of 

 the White, Orange, Yellow, and Red cocci, the charac- 

 ters of which have been briefly discussed above. It will 

 be remembered that the wJiite and orange chromogens 

 resemble the other Paracoccaceae in failing to show the 

 packet grouping, in a generally positive Gram reaction, 

 in forming a surface growth of a not over-vigorous charac- 

 ter, and in fermenting both dextrose and lactose. The 

 yellow and red forms frequently show packets, are gen- 



