IMMUNITY: DIAGNOSIS. 397 



daily when the examination is made some time after the death 

 of the animal. If the animal is examined immediately after 

 death, a few of the bacilli may be present in the peritoneum and 

 pleurae, usually in the form of long motile filaments, but they 

 are almost invariably absent from the blood. A short time after 

 death, however, they spread directly into the blood and various 

 organs, and may then be found in considerable numbers. 



Subcutaneous inoculation with pure cultures of the bacillus 

 of malignant oedema produces chiefly a spreading bloody 

 oedema, the muscles being softened and partly necrosed ; but 

 there is little formation of gas, and the putrid odour is almost 

 absent. 



When the bacilli are injected into mice, however, they enter 

 and multiply in the blood stream, and they are found in con- 

 siderable numbers in the various organs, so that a condition 

 not unlike that of anthrax is found. The spleen also is much 

 swollen. 



The virulence of the bacillus of malignant oedema varies con- 

 siderably in different cases, and it always becomes diminished in 

 cultures grown for some time. To produce a fatal disease, a 

 relatively large number of the organisms is necessary, and these 

 must be introduced deeply into the tissues, inoculation by scari- 

 fication being followed by no result. A smaller dose produces 

 a fatal result when injected along with various other organisms 

 (bacillus prodigiosus, etc.). 



Immunity. — Malignant oedema was one of the first diseases 

 against which immunity was produced by injection of toxins. 

 The filtered cultures of the bacillus in sufficient doses produce 

 death with the same symptoms as those caused by the living 

 organisms, but a relatively large quantity is necessary. Cham- 

 berland and Roux(i887) found that if guinea-pigs were injected 

 with several non-fatal doses of cultures sterilised by heat or 

 freed from the bacilli by filtration, immunity against the living 

 organism could be developed in a comparatively short time. 

 They found that the filtered- serum of animals dead of the dis- 

 ease is more highly toxic, and also gives immunity when 

 injected in small dOses. These experiments have been con- 

 firmed by Sanfelice. 



Methods of Diagnosis. — In a case of supposed malignant 

 oedema, the fluid from the affected tissues ought first to be 



