﻿STUDIES IN PLAGUE IMMUNITY. 271 



Series G4 — Continued. 



immune serum and the mixture injected into the abdominal cavity. Microscopic 

 examination of drops of fluid after twenty minutes showed numerous bacteria 

 with but few leucocytes. No evidence of phagocytosis was present. After sixteen 

 hours the animal was killed. A small amount of sticky fluid was encountered in 

 the abdominal cavity, containing numerous polymorphonuclear leucocytes, the 

 great majority of which did not enclose bacteria. In the few which had ingested 

 pest bacilli, the organisms appeared degenerated. Very few free bipolar staining 

 organisms were present. In the omentum evidences of an extensive phagocytosis 

 existed. However, there were still a number of free bacteria. Some of the 

 bacteria had apparently invaded other organs of the body. 



Guinea, pig number 2855: One-half agar slant culture "Pest Virulent" (from 

 guinea pig number 2704, second transplant) suspended in 1 cubic centimeter of 

 saline solution was inoculated into the abdominal cavity. Microscopic exami- 

 nation of drops of fluid from the abdomen after twenty minutes showed numerous 

 bacteria and comparatively few cells. After one hour a few large mononuclear 

 cells containing bacteria were present. The number of bacteria was considerably 

 diminished. The animal was killed after sixteen hours. Very few bacteria 

 were found in the abdominal exudate. Upon the omentum and surface of the 

 abdominal walls innumerable bacteria were observed. There were moderate 

 numbers of leucocytes present, some of which contained organisms. There were 

 also a number of free bacteria which took the bipolar stain and appeared 

 encapsulated. 



Series 05. — Relating to the mechanism of the action of plague immune sera. 



Guinea pigs numbered 2751, 2800, 2S02, 2804, 2807, 3050, and 3059 were, 

 all inoculated intraperitoneally with 1 cubic centimeter of pest immune serum, 

 mixed with 1 cubic centimeter of a suspension of pest bacilli of the several 

 strains "Pest Virulent," "Maassen Alt," and "Pest Avirulent." Guinea pigs 

 numbered 2803, 2808, 3051, and 3000 were employed for controls and were ino- 

 culated with a suspension of the bacteria to which was added 1 cubic centimeter of 

 saline solution in place of immune serum. Drops of fluid from the abdominal 

 cavities of the animals were examined from time to time, from five minutes to one 

 hour after the inoculation, the animals also being killed at various periods after 

 the inoculation. These examinations demonstrated that the "Avirulent" strains of 

 pest bacilli do to a certain extent become swollen and undergo degeneration under 

 the influence of plague immune serum, outside of the phagocytes. 



However, only a portion of the bacteria inoculated showed these changes, and 

 a typical Pfeift'er's phenomenon with granular destruction of the bacilli does not 

 occur, the degeneration manifesting itself by swelling of the bacilli and their 

 poor and irregular staining reactions. The experiments on these animals also 

 demonstrated the other phenomenon of phagocytosis, etc., encountered in the 

 experiments described in the previous series. 



The individual protocols are not further detailed here, the reults of the 

 experiments having been fully described in general in the text. (See p. 202.) 



