THE GENUS STREPTOCOCCUS 145 



these differences were too slight to offer any satisfactory 

 basis of classification. Migula (1900) listed forty-seven 

 species under the genus Streptococcus, and Le Gros 

 (1902), sixty-three; but most of these "species" are iden- 

 tical in all the important characters described. Minute 

 differences in the appearance of colonies, dryness, granu- 

 lation, outgrowths from the edges, etc., are given diagnos- 

 tic value in certain cases; but these are to be attributed 

 mainly to variations in the conditions of cultivation. Such 

 differences in vitality as are shown by the failure to grow 

 upon potato or on gelatin at 20 degrees also occur; but 

 these can certainly not be considered as of systematic 

 value. One or two fairly definite types have, however, 

 been distinguished by differences in morphology, and in 

 the character of growth in broth. 



Lingelsheim (1891) distinguished two species, Str. 

 longus and Str. brevis, the former characterized by long 

 chains and large flocks in broth, the latter by short chains 

 and diffuse turbidity. Str. brevis was generally not 

 pathogenic, liquefied gelatin slightly, and exerted a strong 

 reducing action on certain dyestuffs. This distinction 

 apparently corresponds to a real division between two 

 types of streptococci. Vincent and others have shown, 

 however, that both morphological characters (the length 

 of chains) and cultural characters (turbidity in broth) 

 are markedly influenced by the reaction of the medium; 

 and even under the same conditions the same strain may 

 exhibit wide variations. 



