IMMUNITY AGAINST MICEOBES. 419 



most of them, whereas Algerian sheep are not affected by the 

 same virus. The virus which may prove fatal to puppies proves 

 harmless to full-grown dogs. 



The result of the inoculation is influenced to a considerahle 

 extent by the fact of the animal having recovered from a previous 

 attack of the same disease, or having been rendered immune 

 against it by artificial means ; much will also depend on the 

 state of the animal's health at the time of inoculation. Fowls 

 which are naturally immune against anthrax take the disease 

 readily if their temperature be artificially lowered by immersion 

 into cold water. Contrariwise, frogs, which are also immune 

 against anthrax, inoculated with the same disease, die when 

 their temperature is artificially raised. Moreover, if the tem- 

 perature of a warm-blooded animal be artificially lowered, or if 

 it be submitted to long-continued fright, the micro-organisms 

 normally present in the intestine pass through the lining 

 epithelium and invade the blood. ^ 



Lastly, much will depend on the mode of introducing the 

 virus. Thus, a quarter of a cubic centimetre of a culture of 

 Bacillus pyocyaneus injected into the veins of a rabbit 

 proves fatal within forty- eight hours ; but the same quantity in- 

 jected under the skin causes deathafter aweekonly,or not at all.^ 



The problem is a very complex one, and in this paper, there- 

 fore, the writer will only make use of data which have been 

 obtained by actual experiments. 



It will be best to discuss in the first place the cases in which 

 the virus produces a well-marked inflammatory reaction at the 

 point of inoculation, when introduced under the skin. We 

 will take, as examples, the cases in which guinea-pigs have 

 been inoculated with virulent quarter-evil (Bacillus Chau- 

 vsei), as being the most typical example of the kind. 



At the end of twelve to eighteen hours after a small quan- 



1 Ch. Bouchard, "Essai d'une Theorie de I'Infection," ' Proceedings of the 

 Teuth Medical Congress,' Berlin, 1890. 



2 Charrin, ' La Maladie Pyocyauique.' Compare also Armand Buffer ' On 

 the Nature of the Disease produced by the Inoculation of the Bacillus pyo- 

 cyaneus.' 



