BIOCHEMICAL FEATURES 83 



it is destroyed by the action of trypsin. In its properties the he- 

 molysin corresponds to the substance contained in the lytic ex- 

 tracts of pneumococci that cause the death of guinea pigs on in- 

 travenous injection. Its activity is prevented by the presence of 

 minute amounts of cholesterol. Following the injection of autoly- 

 sates into rabbits and sheep, the serum of the animal acquires in- 

 creased power of inhibiting the hemolytic action and therefore Cole 

 (1914), 252 whose conclusions these are, believed that the hemoly- 

 sin has antigenic properties ; that it is not simply a product of 

 autolysis but undoubtedly exists preformed in the pneumococcal 

 cell ; it is not given up to the surrounding fluid so long as the 

 bodies of the cocci are intact and, accordingly, is to be considered 

 as a hemolytic endotoxin. 



Previous as Avell as subsequent to the work of Cole, there have 

 been isolated observations of a zone of hemolysis about the colonies 

 of pneumococci on blood agar. Libman, 811 in 1905, demonstrated 

 an organism, probably a pneumococcus, isolated from the blood of 

 a pneumonia patient on the fifth day of the disease, which on blood 

 plates produced a peculiar hemolysis. Later (1922) Hewitt and 

 Famulener 640 described the production of a zone of hemolysis im- 

 mediately around a colony on blood agar of an organism, beyond 

 doubt a pneumococcus, isolated from the blood in a fatal case of 

 septicemia with meningitis following mastoiditis. From their study, 

 Hewitt and Famulener inferred that pneumococci of all serological 

 groups, under certain cultural conditions, may hemolyze human 

 erythrocytes, and that this property apparently is not influenced 

 by the reaction of the medium within the growth limits of the or- 

 ganism nor by prolonged refrigeration of the developed colonies on 

 blood-agar plates. The authors also expressed the opinion, later 

 substantiated by Avery and Neill, that the hemolysin was an intra- 

 cellular product liberated from the autolyzed organisms, which dif- 

 fuses from the colony into the surrounding blood agar. In contra- 

 distinction to the hemolysis of Streptococcus haemolyticus, Hewitt 

 and Famulener called the pneumococcal effect "pseudo-hemolysis." 



