﻿262 STRONG. 



cavity of a guinea pig immunized against plague either by previous vacci- 

 nation or by the injection of a dose of pest immune serum, it was found 

 that Pfeiffer's phenomenon as observed in the case of the cholera organism 

 in the cholera immune animal did not occur. The virulent organism 

 in question did not undergo dissolution and only with the very avirulent 

 strains ("Maassen Alt" and "Pest Avirulent") did the organisms finally 

 become swollen or disintegrated. It is true that shortly after the inocu- 

 lation of the virulent strain in the immunized animal, a disappearance 

 of the bacteria from the abdominal cavity usually occurred, and that 

 also at first but few animal cells were encountered in the abdominal 

 exudate. Upon investigating the fate of the bacteria by killing the 

 animals at different periods of time after the inoculation, it was found 

 that shortly after the injection, both in the case of animals immunized 

 against pest and in that of normal animals, the majority of the bacteria 

 had been carried to or made their way to the walls of the cavity and 

 particularly to the omentum, to the surface of which they had become 

 adherent. Here man) r of them were taken up by the phagocytic cells. 

 After a short period, the leucocytes became more abundant in the abdom- 

 inal exudate and many of them were seen to contain bacteria. In many 

 cases, in the immunized animal, the leucocytes seem to possess positive 

 chemotaxis for the bacteria, judging from the manner in which the latter 

 are grouped about them. 



In the case of nonimmune animals the pest bacilli outside of the 

 cells increase in number up to the time of the death of the animal. 

 The majority of the bacteria that are found to exist free in the cavity 

 after the negative phase, are short, bipolar staining bacilli which seem 

 to possess capsules ; a smaller number of large bacilli, frequently showing 

 involution forms, are also encountered. After the negative phase in 

 the case of the immunized animal, the leucocytes usually become much 

 more numerous in the abdominal cavity. The phagocytosis of the bac- 

 teria continues, both by the cells in the omentum, and by those free in 

 the abdominal cavity, until very few free bacilli remain. However, as 

 has been mentioned, in the nonimmune animals the bipolar staining 

 organisms, which do not appear to be taken up by the leucocytes, increase 

 up to the time of the death of the guinea pig. (See Series 63, 64, and 

 65 (pp. 268, 270, and 271.) 



Lohlein,™ whose article was published while my experiments were in 

 progress, also encountered these bipolar staining organisms. These he 

 very appropriately terms "bacteria of the second generation," and he calls 

 attention to the fact that they are seldom seen to undergo phagocytosis. 

 This phenomenon as mentioned he explains either upon the assumption 

 that some such substance as the aggressin of Bail may be present, or that 



79 Loc. tit. 



