ABSTEACTS 575 



Immunity Factors in Pneumococcus Infection in the Dog. C. G. Bull. 



(Jour. Exp. Med., 1916, 24, 7-24.) 



Intravenous inoculations of from 1 to 3 cc. per kilo of body weight 

 of a bouillon culture of virulent pneumococci produce septicemia and 

 meningitis in dogs. The injected penumococci leave the circulation 

 rapidly, but begin to reinvade the blood from twenty-four to forty- 

 eight hours later. The septicemia reaches its chmax between the fourth 

 and fifth days and then abruptly declines, the blood becoming sterile 

 within from one to three days after the height of the septicemia is 

 reached. The initial disappearance of the pneumococci from the circu- 

 lation has been found to be due to agglutination of the diplococci in the 

 blood stream and accumulation of the clumps in the lungs, liver, spleen, 

 etc. If the dogs are reinoculated during the ascension of the septi- 

 cemia, the injected diplococci leave the circulation as rapidly as in nor- 

 mal dogs. Cultures isolated in this stage of the infection, both before 

 and from threfe to four hours after the reinoculation, are resistant to 

 the agglutinins and opsonins of immune sera that agglutinate and opso- 

 nize the cultures with which the dogs were originally infected. Thus 

 it follows that the pneumococci are able to reinvade the circulation be- 

 cause they have acquired a fastness to the existing antibodies and not 

 because the antibodies have been exhausted. By reinoculating dogs 

 at the time of the crisis in the septicemia it has been shown that 

 the agglutination of the pneumococci is more rapid and complete 

 and that the diplococci leave the circulation much more rapidly than 

 in normal dogs. Hence acquired antibodies are operative within the 

 animals at this time although they cannot be demonstrated in vitro 

 until from twenty-four to forty-eight hours later, Pneumococci iso- 

 lated as the infection is subsiding are more susceptible to the action of 

 inmiune sera than the original cultures injected. It is probable that 

 all the dogs would have survived the infection if a meningitis had not 

 developed. In the acutely fatal cases of meningitis few pneumococci 

 are phagocyted, while in the milder and convalescent cases much pha- 

 goc3rtosis occurs. It is suggested that the incubation period of infec- 

 tious diseases is due to the fact that the infecting agents must become 

 adapted to the adverse conditions encountered in the newly infected 

 host before they can multiply sufficiently to produce the symptoms of 

 disease. It is further suggested that epidemics may arise because the 

 infectious agent is passed from person to person in the ascending stage 

 of the disease and thus enters new hosts in a state of maximum resist- 

 ance to the natural antibodies of such individuals. When early con- 

 tacts are avoided, epidemics tend to subside because the infectious 

 agent is weakened by the action of acquired antibodies during the 

 period of convalescence. — B. W. 



