240 Chapter VIII 



in the act of devouring bacilli. In the normal, susceptible rabbit, 

 on the other hand, the exudation produced is soft, rich in fluid, and 

 very poor in leucocytes. The vessels in the vicinity are distended with 

 blood, and the fact that the leucocytes do not come up to the seat of 

 inoculation is in no way due to the absence of vascular dilatation 

 which might prevent diapedesis. The vessels are much more dilated 

 than in the vaccinated rabbit, and yet in the latter the emigration is 

 incomparably greater. This essential difference must be attributed 

 to the sensitiveness of the leucocytes, which exhibit a negative 

 chemiotaxis in the normal rabbit but a very marked positive chemio- 

 taxis in the vaccinated rabbit. 



It has been shown repeatedly that the subcutaneous exudation, 

 very rich in leucocytes which have had time to ingest all the bacilli, 

 when inoculated into guinea-pigs, ensures the appearance in them 

 of a generalised and fatal anthrax; this affords evidence that the 

 phagocytosis is exercised against virulent and therefore living bacilli. 

 Marchoux 1 , in Roux's laboratory, has carried out numerous experi- 

 ments on the vaccination of rabbits and has observed that the 

 inoculated anthrax bacilli cause an exudation very rich in leucocytes, 

 and that these cells ingest and destroy the bacilli. The phagocytes 

 easily rid the refractory animal of the bacilli in the vegetative state, 

 but the spores are much more resistant. After being devoured by the 

 leucocytes they may remain inside them for months without germinat- 

 ing. Marchoux obtained cultures of anthrax from the subcutaneous 

 exudation taken from vaccinated rabbits 70 days after inoculation. 



The fact that the bactericidal action of the blood serum on 

 [253] anthrax bacilli is specially well marked in the rat, suggested the 

 idea of trying to obtain, in this rodent, an augmentation of this 

 property as a result of vaccination. Sawtchenko 2 attempted to do 

 this in an investigation already cited in Chapter VI, carried out in 

 my laboratory. He succeeded in thoroughly vaccinating white rats 

 against virulent anthrax and in showing that the blood serum of these 

 animals rendered refractory " is bactericidal in the same degree as that 

 of non-immunised rats." In the vaccinated rats "the subcutaneous 

 exudation was as free from bactericidal substances as was the lymph 

 of the control animals." Sawtchenko was unable to demonstrate any 

 increase of bactericidal power except in the peritoneal exudation of 

 rats vaccinated by injection of cultures into the peritoneal cavity. 



1 Ann. de VInst. Pasteur, Paris, 1895, t. ix, p. 805. 



2 Ann. de VInst. Pasteur, Paris, 1897, t. xi, p. 881. 



