332 PATHOGENIC MICROORGANISMS 



but will not agglutinate any of the non-pathogenic members of 

 either group. l 



Active immunization of human beings suffering from staphylococcus 

 infections has been extensively practiced by Wright, in connection with 

 his work on opsonins. There can be no question about the fact that the 

 )psonic substances in the blood are increased by the injection of dead 

 staphylococci. The procedure is of therapeutic value in subacute and 

 :-hronic cases. The work of Hiss on the use of leucocyte extracts in 

 animals infected with Staphylococcus pyogenes aureus -has given en- 

 couragement for such treatment in human beings. A number of 

 staphylococcus infections in man have been successfully treated with 

 leucocyte extract by Hiss and Zinsser. 



STAPHYLOCOCCUS PYOGENES ALBUS 



This coccus differs from Staphylococcus pyogenes aureus simply in 

 the absence of the golden yellow coloration of its cultures. Morpho- 

 ogically, culturally, and pathogenically, it is in every way identical 

 kvith the staphylococcus described in the preceding section, but its 

 :oxin- and enzyme-producing powers in general are less developed than 

 ;hose of the aureus variety. Its close biological relationship to aureus 

 s furthermore demonstrated by its agglutination^J^Japhylococcus 

 Dyogenes aureus immune sera. 



STAPHYLOCOCCUS EPIDERMIDIS ALBUS 



The Staphylococcus epidermidis albus described by Welch is merely 

 me of the non-pathogenic varieties of Staphylococcus pyogenes albus 

 ind possibly does not deserve separate classification. It may give rise 

 ,o unimportant stitch abscesses. 



STAPHYLOCOCCUS PYOGENES CITREUS 



Staphylococcus pyogenes citreus produces a bright yellow or lemon- 

 ;olored pigment of distinctly different hue from that of Staphylococcus 

 >yogenes aureus. It may be pyogenic and in every way similar to 

 Jtaphylococcus pyogenes aureus, but is less often found in con- 

 Lection with pathological lesions than either of the preceding staphy- 

 ococci. 



1 Proscher, Deut. med. Woch., xi, 1903. 



