1 68 RELATIONSHIPS OF THE COCCACE^E 



into groups by their quantitative power of fermenting 

 dextrose and lactose. Sixty-one cultures showed an 

 average acid production of 1.9 per cent normal in dextrose 

 broth and 1.4 per cent normal in lactose broth. The 

 mode in each case was near the lower end of the scale, 

 indicating that the strong acid-producers are " variants by 

 addition " from less active types. One point which deserves 

 further investigation is an apparent correlation between 

 high acid production and a positive reaction to the Gram 

 stain. In our small series of cultures it was apparently 

 true that these two properties were definitely associated, 

 negative Gram reactions being observed only with cul- 

 tures of slight acid-producing power. 



There is one type of streptococcus, besides the six de- 

 scribed by Andrewes and Horder, which seems at present 

 sufficiently well marked to deserve specific rank. The 

 best basis for species — and the only satisfactory basis — 

 is a study of the frequency with which various types occur, 

 specific names being given to the centers of variation. 

 When, however, some strains exhibit a highly peculiar char- 

 acteristic we may recognize a provisional species, pending 

 comparative studies, if the property be sufficiently definite 

 and of fairly common occurrence. Such a provisional 

 specific type seems warranted in the case of the lique- 

 fying streptococci. 



A slight liquefying power has been noticed, again and 

 again, in exceptional strains of streptococci, {Str. Brightii, 

 Trevisan, Str. enteritidis , Escherich, Str. Bonvicini, Ches- 



