84 BIOLOGY OF PNEUMOCOCCUS 



Takami 1372 described a zone of hemolysis about the colonies of all 

 the sixty strains of pneumococci plated on blood agar. This zone 

 was separated from the periphery of the colony by a greenish 

 zone ; it appeared on standing at room or ice-box temperature and 

 in time might spread over the whole plate. 



Avery and Neill 58 made further studies on this property of 

 Pneumococcus. Extracts of pneumococci prepared in broth, or 

 from washed pneumococci made with phosphate solution and fil- 

 tered through Berkefeld candles, were actively hemolytic for rab- 

 bit erythrocytes. The hemolysin was destroyed by ten minutes' 

 heating at 55°. The conclusions of the authors were: 



When pneumococcus extracts are exposed to air, the hemotoxin is 

 destroyed only in those extracts capable of undergoing auto-oxidation. 

 The active agent responsible for this destruction is probably a peroxide 

 formed by the union of molecular oxygen with some other easily oxi- 

 dizable constituents of the extracts. 



In another study, Neill 051 mixed pneumococcal extracts, in which 

 the hemotoxin had previously been inactivated by oxidation, with 

 B. coli and anaerobic Bacillus T, sealed and incubated the extracts 

 thus treated for several hours. Titration of the bacteria-free su- 

 pernatant fluid obtained by centrifuging this mixture showed that 

 the inactive oxidation product of pneumococcal hemotoxin was re- 

 converted to an actively hemolytic substance by the action of those 

 bacteria, which were not themselves hemolytic. The reduction was 

 also accomplished by sodium hyposulfite. The active lysin, or hemo- 

 toxin, produced by the reduction of the inactive oxidized extracts 

 was shown to be identical with the original active hemotoxin, since 

 it possessed the same degree of thermolability and was neutralized 

 by the same specific antibody. Pneumococcal hemolysin or hemo- 

 toxin is, therefore, not an artificial cleavage product but a natural 

 substance originating within the cell. Normal serum, egg albumen, 

 cholesterol, and peptone, according to Weiss, 1509 inhibit hemolytic 

 activity. 



