156 Chapter VI 



blood when removed from the organism? From numerous experi- 

 [165] ments, carried out by Hankin 1 and by Roux and myself 2 , it has been 

 demonstrated that the bactericidal power of the fluids of the rat 

 cannot be invoked as the cause of the animal's resistance to anthrax. 

 Those rats which show themselves very susceptible to this disease and 

 die from anthrax infection, furnish, nevertheless, a serum that will 

 prevent anthrax in other rats, and which will protect even mice into 

 which the bacilli have been injected. Rats into which we inoculate 

 on one side of the body a little anthrax culture, and on the other 

 side the same quantity of bacilli mixed with blood serum from the 

 same animal, manifest oedema at the former place only. It is from 

 this latter point that the general infection takes place, the side where 

 the anthrax bacilli mixed with serum was introduced remaining 

 unaffected. Sawtchenko 3 , who has investigated the immunity of the 

 rat in my laboratory, has to the facts just mentioned added the 

 observation that when the injection of bacilli causes haemorrhage 

 the rat survives. When, on the contrary, the injection is made with 

 a fine needle and without effusion of blood, the rat contracts a 

 fatal anthrax. 



It follows from these facts that the blood, immediately it has 

 [166] escaped from the vessels, undergoes a change in its composition and 

 becomes bactericidal for the anthrax bacillus, whilst, when it is circu- 

 lating in the organism, it exhibits no such power. Sawtchenko has 

 studied the substance in the serum which kills the bacilli and has 

 demonstrated that it will resist heating to 56 C.; even when heated 

 to 61 C. the serum still exercises a certain amount of bactericidal 

 power for very attenuated bacilli (Pasteur's first vaccine). Researches 

 on the distribution of this bactericidal power in the living rat have 

 convinced Sawtchenko that none of it passes into the fluid of the 

 passive oedema set up by the slowing of the circulation, nor into that 

 of the active oedema developed as the result of the inoculation of 

 anthrax bacilli. He observed that even the bacillus of Pasteur's first 

 vaccine grows abundantly in the oedematous fluid produced by the 

 injection of virulent bacilli. The peritoneal lymph, however, exerts 

 a very marked bactericidal action on the bacilli., Having demon- 

 strated this fact Sawtchenko put to himself the question : May not 

 the great difference between the action of these fluids depend on the 



1 CentralU.f. Bacterial, u. Parasitenk., Jena, 1891, Bd. ix, SS. 336, 372. 



2 Ann. de VInst. Pasteur, Paris, 1891, t. v, p. 479. 



3 Ann. de VInst. Pasteur, Paris, 1897, t. xi, p. 865. 



