ANTIBODIES TO PNEUMOCOCCUS 363 



brought about a marked decrease in the agglutinative ability of 

 the cultures in the presence of homologous serum, and caused the 

 development of agglutinability with heterologous serum. The 

 changes appeared irregularly and suddenly. Megrail and Ecker, 888 

 on the contrary, claimed that Type I Pneumococcus in contact 

 with Type I serum resisted the immunological change, as did the 

 same organism when passed through a series of sterile abscesses 

 artificially produced in mice and rats. 



As has already been explained in Chapter V, the dissociation of 

 typical pneumococci into degraded variants is accompanied by a 

 loss of type-specificity and the development of species-specificity 

 in the agglutinative properties of the organism. When the de- 

 generative process has not extended too far and the organism is 

 then appropriately stimulated by animal passage with the accom- 

 paniment of vaccines of typical strains or by growth in antirough 

 serum, the organism may develop type-specific agglutinogens as it 

 approaches the parent strain in its biological characters. 



AGGLUTININS IN THE BLOOD OF ANIMALS 



Bull (1915-1916) 170 ' 172 " 4 ascribed to agglutinins a decisive part 

 in the resistance of animals to pneumococcal infection. He found 

 that the injection, of small quantities of specific antipneumococcic 

 serum brought about almost instantaneous and specific agglutina- 

 tion of pneumococci in the circulation of infected rabbits. In all 

 instances of both natural and passive immunity investigated, ag- 

 glutination of the bacteria within the blood of the infected animal 

 was followed by the rapid removal of the agglomerated cocci from 

 the circulation and their destruction either by phagocytosis or in 

 the capillary systems of the viscera. Unagglutinated pneumococci 

 might remain in the blood stream and produce a progressive sep- 

 ticemia. 



There could be found only one reference in the literature to the 

 possible effect of an alien infection on agglutinins in the blood of 



