538 INFECTION AND IMMUNITY. 



ing are often seen to consist of two hemispheres, 

 which are separated by a delicate cleft. In pus 

 they are found in small groups of two to nine or 

 ten, ocasionally as diplococci, tetrads or very short 

 chains. 

 cultivation They are luxuriant growers on nearly all media 



and Biologic ,. t_ -.L i i j> i_ 



properties, which are suitable for bacteria, preferring, how- 

 ever, a slightly alkaline reaction. Growth is best 

 in the presence of oxygen, but proliferation occurs 

 in its absence. Sputum, serum and ascitic fluid 

 are favorable media, and in the last two the cocci 

 may be agglutinated. An alkaline reaction is pro- 

 duced in litmus milk, and the casein is precipitated 

 and partly digested. The production of a proteo- 

 lytic ferment is shown by liquefaction of gelatin 

 and the formation of a clear zone about the colo- 

 nies when grown in plates which contain coagulat- 

 ed serum (Loeb, cited by Neisser and Lipstein). 

 Albumin is changed into peptone. Loeb distin- 

 guishes between a ferment which liquefies gelatin 

 (gelatinase, a "collolytic" ferment), and one which 

 digests albumen (tryptic ferment). Gelatinase is 

 present in staphylococcus filtrates and normal 

 serums are rich in antibodies for it. A fat-splitting 

 ferment (lab ferment) is also present in the 

 filtrates. The fact that the pus which is produced 

 in staphylococcus infection does not coagulate may 

 be due to the action of the proteolytic ferment, 

 which digests the fibrinogen. 



Van der Velde had noted in 1894 that "staphy- 

 lotoxin" (staphylococcus filtrates) cause hemoly- 

 sis. Neisser and Wechsberg, in 1901, by growing 

 the organisms in bouillon of suitable alkalinity, 

 obtained hemolytic filtrates, giving the name of 

 staphylolysin to the hemolytic principle. The hemo- 



