BIOCHEMICAL FEATURES 85 



Returning to the original observation of Cole that active or 

 reduced pneumococcal hemotoxin is antigenic, Neill 952 in 1927 re- 

 ported that "a neutralizing antibody may be produced by im- 

 munization with the hemolytically inactive hemotoxin present in 

 oxidized solutions as well as by immunization with the active toxin. 

 The antibody is a species-specific antihemotoxin neutralizing the 

 hemotoxin from all types of pneumococci." Neill also showed that 

 the hemotoxin is independent of the bacteriolytic enzyme present in 

 pneumococcal cells. In the next year, Cotoni and Chambrin 282 con- 

 firmed the data reported by Cole and by Avery and Neill, and de 

 scribed a simple method for the quantitative measurement of the 

 hemolytic power of Pneumococcus. While Cotoni and Chambrin 

 were able to make satisfactory determinations on a number of 

 strains, they reported that the quantity of hemoglobin liberated 

 did not follow the law of multiple proportions and that strains 

 varied in their hemolytic action. To the authors there appeared to 

 be no difference in the susceptibility of the blood cells of man, rab- 

 bit, guinea pig, cow, pig, horse, or sheep to pneumococcal hemoly- 

 sin. They also gave a method for titrating the antihemolytic 

 power of immune serum. 



Sickles and Coffey 1280 published a paper on a hemolytic sub- 

 stance in pneumococcal culture broth. No proof was presented 

 that this substance is not the same as the hemolysin already dis- 

 cussed, but Sickles and Coffey, like Neill, and Cotoni and Cham- 

 brin, found that pneumococcal immune serum had a marked inhib- 

 itory effect on hemolysis, giving complete inhibition in a 1 to 1,000 

 dilution, whereas normal horse serum was effective only in a 1 to 

 400 dilution. 



The belief of Cole and his associates that hemolysin is an intra- 

 cellular constituent of Pneumococcus was not shared by Cowan. 287 

 On the contrary, this author stated positively that the principle is 

 extracellular and arises during the growth of the organism in fluid 

 media. Its highest titer occurred immediately after the maximal 

 period of multiplication — phase of logarithmic growth — while the 



