﻿STUDIES IN TLAGUB IMMUNITY. 269 



Series 63 — Continued. 



were dried and stained and others were examined in a fresh condition. On micro- 

 scopic examination there was no evidence whatever of bacteriolysis either in 

 the fluid from the animals immunized and inoculated with immune serum or 

 in that from the control animal (number 2758) although there was a diminution 

 in the number of the bacteria which had been inoculated in the exudates from all. 

 Those organisms which were present stained naturally and presented no evidence 

 of degeneration. 



The leucocytes were much more numerous in the preparations from animals 

 numbered 2152 and 2153, fewer in number in those from animal number 2757 

 and still more scanty in those from animal number 2758. At a later period a 

 still more marked reduction of the number of the bacteria in the abdominal 

 exudate from all the animals occurred. This reduction, however, was more 

 marked in the animals which had received the serum. On the following morn- 

 ing the guinea pigs were all killed with chloroform and the abdominal cavity 

 in each instance immediately opened and its contents examined. In guinea 

 pig number 2152 there was almost no local reaction apparent about the point 

 of inoculation. The abdominal cavity contained a small amount of a tenacious 

 fluid. Cover slips from this exudate stained with methylene blue showed a 

 considerable number of polymorphonuclear and large mononuclear -leucocytes, the 

 latter variety predominating. None of the leucocytes contained any bacteria 

 and no bacteria were found free in the exudate. A small portion from the edge 

 of the omentum was cut off and rubbed over a glass slide and the preparation 

 stained with methylene blue. This specimen showed innumerable polymorpho- 

 nuclear leucocytes and large, mononuclear, endothelial phagocytes, the majority 

 crowded with pest bacilli. There were a number of free organisms, but these 

 were swollen and frequently stained irregularly and usually faintly so in color. 

 They showed no capsules and no bipolar staining. Many appeared as involution 

 forms. It seems likely that a number of these organisms have been extruded from 

 cells or that the cells have burst and become destroyed and the bacteria have 

 escaped. This opinion is supported by the fact that many bacilli with a similar 

 appearance were seen within degenerating cells or lying about them. 



It appears evident that the bacteria have become acted upon in some manner by 

 the immune serum so that the cells of the omentum to which the bacteria have 

 been attracted are enabled to pick them up in large numbers. It would seem that 

 the great reduction in the number of bacteria in the abdominal cavity during the 

 first hour after inoculation is not due to the fact that the bacteria have been des- 

 troyed but because they have been attracted to the omentum as to a sponge. That 

 the bacteria inside the leucocytes were not all dead was demonstrated by placing 

 some of the leucocytes containing ingested bacilli upon agar cultures. It was 

 then found that when the leucocyte was removed from its natural conditions in 

 the animal body the bacteria sometimes apparently multiplied within the cell 

 and finally burst and destroyed it. The phagocytic cells of the omentum evidently 

 play an important part in pest immunity. In guinea pigs numbered 2153 and 

 2757' very much the same conditions were observed as in number 2152. The cells 

 of the omentum perhaps contained not so many bacteria and there were a few 

 leucocytes in the abdominal cavity which contained a few ingested bacilli. In 

 number 2757 there was not as much exudate present as in number 2152. The local 

 reaction about the point of inoculation was also more marked in guinea pig number 

 2757, there being a hemorrhagic area about 2 cubic centimeters in diameter about 

 the point of inoculation. In guinea pig number 2758 there was a very marked 

 local reaction about the point of inoculation with extensive haemorrhages in the 

 tissues. In this animal there was practically no fluid in the abdominal cavity 

 although there were some flakes and masses of fibrin containing a fair number of 



