164 WINSLOW, ROTHBERG AND PARSONS 



From this standpoint it is evident that by far the commonest 

 homogeneous type among the staphylococci is that which in- 

 cludes the orange, liquefying, actively fermenting strains. Forty- 

 one of our 180 cultures were of this type and as shown by the 

 detailed characteristics presented in group 7 of table 10 these 41 

 strains were remarkably uniform in all their properties except the 

 clotting and liquefaction of casein in milk. Of the 203 strains 

 of staphylococci studied by the Winslows 126 were of this type 

 (if we ignore the distinction based on reduction of nitrates) . It 

 seems quite evident that this organism is the most abundant form 

 among the staphylococci and the natural center about which all 

 the other types are grouped. Assuming the distinction between 

 Aur. aureus and Aur. mollis on the basis of nitrate reduction to be 

 unwarranted, this central type of the staphylococcus group should 

 certainly bear the name Staphylococcus aureus; and all the other 

 types of the genus may be assumed to have been derived from this 

 one by the loss of one or more of the characteristics of the primi- 

 tive form. 



Among the types which have retained the orange pigment 

 production but which fail either to liquefy gelatin or to fer- 

 ment lactose, none has occurred with sufficient frequency in 

 the present series of strains to appear deserving of specific rank 

 (see table 8 and groups 8 to 12 in table 10). Dudgeon's orange 

 chromogens were also practically all alike in liquefying gelatin 

 and fermenting lactose. On the other hand the Winslows found 

 49 strains in their series which produced orange pigment but 

 failed to liquefy gelatin or ferment lactose identifying the type 

 as Aur. aurantiacus. We may perhaps recognize this species 

 (group 8, table 10) as Staphylococcus aurantiacus leaving the other 

 two types, characterized respectively by gelatin liquefaction and 

 failure to ferment lactose, and by lactose fermentation and fail- 

 ure to liquefy gelatin, (as well as the groups characterized by 

 miscellaneous fermentative reactions) without specific names. 



The series of white pigment formers appears from all the in- 

 vestigations to be much more variable in its reactions. Of the 

 six groups represented in the third column of table 8 three are 

 represented by 18 or more strains out of the 100 white strains 



