382 BIOLOGY OF PNEUMOCOCCUS 



the differences in the immunological behavior of immune horse and 

 rabbit serum. 



Inasmuch as complement fixation does not occur in the absence 

 of particulation and since particulation is a secondary phenome- 

 non in the reaction, the authors regard complement fixation as a 

 tertiary manifestation. 



The evidence presented in the communications cited and in other 

 reports is sufficient to demonstrate that the method of complement 

 fixation offers no advantages over other serological methods for 

 the identification of pneumococci or of types within the species. 



Bactericidins 

 With the advancement of bacteriological knowledge, the pneu- 

 mococcidal action of both normal and immune serum has been 

 found to be a more complicated process than it was earlier con- 

 ceived to be. Instead of being solely a function of possible bac- 

 tericidins in serum, the destructive effect of blood involves the ac- 

 tion not only of serum but of leucocytes and of fixed tissue cells. 

 Since the pneumococcidal power of blood depends on the asso- 

 ciated participation of tropins or opsonins and phagocytes, the 

 special features of their combined action will be described later in 

 the present chapter, while the nature of other inherent defenses of 

 the animal body will be discussed in a subsequent chapter. 



Antihemotoxin 

 Experiments on the antigenic action of pneumococcal hemo- 

 toxin reported in 1914 by Cole 252 indicated that the serum of rab- 

 bits and sheep immunized with hemolytic extracts of Pneumococ- 

 cus had acquired increased power to inhibit the lytic effect of the 

 extract on erythrocytes. In studies on the oxidation and reduction 

 of immunological substances, Neill 952 and his colleagues 958 " 9 com- 

 pared the immunological response to the injection into rabbits of 

 reduced and oxidized pneumococcal extracts, and succeeded in 

 producing a neutralizing antibody by immunizing the animal with 



