RESEARCHES ON CERTAIN PROBLEMS OF PLAGUE IMMUNITY 39 



where highly virulent bacilli are injected, phagocytosis is the only agency 

 at work in their destruction. 



The writer's experience and results are largely in agreement with 

 Markl's, but, as already mentioned, in dealing with the subject of 

 bacteriolysis in vitro, evidence of complete destruction of the bacilli, 

 even of low virulence, could not be obtained. The results observed by 

 Markl when the bacilli were injected into the peritoneum can also be 

 obtained in the subcutaneous tissue. The writer has found that when a 

 bacillus of high virulence is injected into the subcutaneous tissue of the 

 abdomen, or where infection is caused by shaving the skin and rubbing 

 the culture on the shaved area, i.e., by the cutaneous method, an enormous 

 multiplication of the bacilli takes place within the lymph spaces, which 

 become distended with lymph in the vicinity of the point of inoculation. 

 Microscopical preparations from this region show a complete, or almost 

 complete, absence of leucocytes. On the other hand, if the animal has 

 been immunised by an injection of anti-plague serum, given say 24 hours 

 before the injection of the bacilli, instead of the diffuse indefinite swelling, 

 or absence of any swelling, visible to the naked eye found in the 

 unprepared rat, a well marked generally sharply circumscribed swelling 

 is observed, and microscopical examination shows in it the presence of an 

 enormous number of polymorphonuclear leucocytes, many of which are 

 packed with bacilli. Animals in which this condition is observed either 

 recover or die at a much later period than the controls. 



Summary. 



Toxins can be demonstrated in the filtrates of bouillon cultures of 

 the B. pestis. These toxic substances are probably set free by the 

 disintegration of the bacillus through autolysis, but, since Albrecht and 

 Ghon and Markl were able to demonstrate their presence in young 

 cultures, the possibility is not excluded that they are toxins in the 

 narrower sense, i.e., secretory products of the bacillus. The toxin is 

 much more toxic for the rat and mouse than for the rabbit and guinea- 

 pig. The toxicity for mice is destroyed by heating to 70° C. for 30 

 minutes. 



Under certain conditions, the injection of toxin stimulates the animal 

 body to the formation of antitoxin, and the experiments recorded here 



(149) 



