452 BIOLOGY OF PNEUMOCOCCUS 



immunological action of an antigen prepared by combining the 

 capsular polysaccharide of Type III Pneumococcus with horse 

 serum globulin, fully justify the conclusion that it is the soluble 

 specific carbohydrate which determines the type-specificity of the 

 hypersensitive state and of the anaphylactic reaction. 



The contrasting differences in the sensitizing properties of se- 

 rum from the immune rabbit and the immune horse were studied by 

 Mehlman and Seegal (1934). S89 In conformity with the results of 

 Avery and Tillett, guinea pigs injected parenterally with anti- 

 pneumococcic rabbit serum were thrown into anaphylactic shock 

 by the intravenous injection twenty-four hours later of the capsu- 

 lar carbohydrate of pneumococci corresponding in type to that of 

 the immune serum. Guinea pigs similarly prepared with antipneu- 

 mococcic horse serum were not susceptible to an otherwise shock- 

 ing dose of the homologous antigen. Uteri removed from guinea 

 pigs sensitized passively with the immune rabbit serum contracted 

 characteristically on contact with the homologous specific carbo- 

 hydrate, whereas uteri of guinea pigs injected with immune horse 

 serum failed to react in this manner. Tests made to determine a 

 possible anti-alexic activity of parenterally injected antipneumo- 

 coccic rabbit and horse serum failed to show any marked differ- 

 ence between the two serums. In a second communication, Mehl- 

 man and Seegal 890 demonstrated in mice the same difference be- 

 tween the sensitizing property of antipneumococcic serum from 

 the rabbit and from the horse. The sensitizing property of immune 

 rabbit serum appeared to be independent of protective action, 

 since the serum of both the immune rabbit and horse were equally 

 effective in curing mice of infection with Pneumococcus.* 



The comparative inability of antipneumococcic horse serum to 

 sensitize the guinea pig passively to Pneumococcus is also evident 

 when sensitivity is tested by intracutaneous injection of soluble 

 specific substance. According to Mehlman and Seegal (1934), 



* Differences in the nature of antibodies in immune rabbit and horse serum 

 have been discussed in Chapter XI. 



