428 BIOLOGY OF PNEUMOCOCCUS 



latus (Pneumococcus). The animals were killed during successive 

 stages of infection and the lungs examined for cellular changes. 

 The differences in the physiological response corresponded with 

 the natural susceptibility of the animal species to infection. In 

 non-refractory animals, the cocci caused only a feeble local in- 

 flammatory reaction with little phagocytosis, and the leucocytes 

 neither engulfed the organisms nor inhibited their growth. In re- 

 fractory animals, on the contrary, a more or less pronounced 

 local inflammatory process developed, with leucocytic migration 

 and accompanying phagocytosis. When the injections were made 

 into the anterior chamber of the eye, there appeared to be no dif- 

 ference in the reaction of the aqueous humor of the animals of the 

 two classes, since the fluid served as a medium for the growth of 

 the injected cocci. 



Opposed to the observations of Tchistovitch were those of Behr- 

 ing and Nissen, 98 published in the same year, who could find no 

 differences in the bactericidal properties of the serum of mice, rats, 

 and rabbits. The inability of the serum of the animals to affect 

 pneumococci was in marked contrast to their destructive action on 

 anthrax bacilli. Wadsworth 1455 also (1903) was unable to discover 

 any parallelism between the action on pneumococci of serum from 

 normal animals and the natural resistance of the animals to pneu- 

 mococcal infection. When tested by agglutination and precipita- 

 tion methods, the serums in low dilutions showed no significant 

 differences. 



Natural immunity of the pigeon to Pneumococcus, according to 

 Strouse (1909), 1345 was due to high normal body temperature and 

 not to any specific tissue reaction. Employing both in vitro and 

 in vivo methods for studying phagocytosis, Strouse could detect 

 no difference in the reaction of pigeons and of mice to experi- 

 mental infection. Ungermann 1434 also studied the phenomenon of 

 phagocytosis occurring after the addition of serum of various 

 animal species to leucocytes of animals of homologous and heter- 



