SUSCEPTIBILITY AND IMMUNITY. 243 



and Roger found that white rats, which are unsusceptible to anthrax, 

 became infected and frequently died if they were exhausted, previous 

 to inoculation, by being compelled to turn a revolving wheel for a 

 considerable time. Pasteur found by experiment that fowls, which 

 have a natural immunity against anthrax, become infected and per- 

 ish if they are subjected to artificial refrigeration after inoculation. 

 This has been confirmed by the more recent experiments of Wagner 

 (1890). According to Canalis and Morpurgo, pigeons which are en- 

 feebled by inanition easily contract anthrax as a result of inocula- 

 tion. Arloing states that sheep which have been freely bled con- 

 tract anthrax more easily than others ; and Serafini found that when 

 dogs were freely bled the bacillus of Friedlander, injected into the 

 trachea or the pleural cavity, entered and apparently multiplied to 

 some extant in the blood, whereas without such previous bleeding 

 they were not to be found in the circulating fluid. 



Again, as already stated in a previous section, the simultaneous 

 injection of certain chemical substances overcomes the vital resist- 

 ing power of the tissues or fluids of the body in such a way that 

 infection and death may occur as a result of inoculations into animals 

 which have a natural or acquired immunity against the pathogenic 

 microorganism introduced. Thus Arloing, Cornevin, and Thomas 

 have shown that rabbits succumb to symptomatic anthrax when lac- 

 tic acid is injected at the same time with the bacillus into the muscles. 

 Nocard and Roux have obtained the same result by injecting various 

 other substances, and their experiments show that the result is due 

 to the injurious effects of the substance injected upon -the tissues, 

 and not to an increased virulence on the part of the pathogenic ba- 

 cillus. The experiments of L3O are of a similar nature. By inject- 

 ing phloridzin into rats he caused them to lose their natural immu- 

 nity against anthrax. Certain anaesthetic agents have also been 

 shown to produce a similar result. Platania communicated anthrax 

 to immune animals dogs, frogs, pigeons by bringing them under 

 the influence of curare, chloral, or alcohol ; and Wagner obtained a 

 similar result in his experiments on pigeons to which he had admin- 

 istered chloral. 



More direct experimental evidence in favor of the view under con- 

 sideration is that obtained by Beumer in his experiments with steril- 

 ized cultures of the typhoid bacillus. He found that after the re- 

 peated injection of non-lethal doses mice were able to resist an 

 amount of this toxine which was fatal to animals of the same spe- 

 cies not so treated. But, on the other hand, Gamaleia found, in his 

 experiments upon guinea-pigs which had been made immune against 

 the pathogenic action of a spirillum, called by him Vibrio Metschni- 

 kovi, that these animals have no increased tolerance for the toxic 



