CHAPTER IX 



THE PATHOGENICITY OF JOHNE'S BACILLUS : INOCU- 

 LATION EXPERIMENTS WITH INFECTED MATERIAL 

 —INOCULATION EXPERIMENTS WITH PURE CUL- 

 TURES OF JOHNE'S BACILLUS— THE PATHOGEN- 

 ICITY OF THE BACILLUS FOR SMALL ANIMALS 



Inoculation Expepiments with Infected Material. — As 



no cultures of Johne's bacillus were available at the 

 time, all the early experiments regarding the patho- 

 genicity of the bacillus were performed with infective 

 material that was obtained at post-mortem examina- 

 tion. 



The first to carry out systematic experiments in this 

 direction were Johne and Frothingham, who sought to 

 prove the tubercular nature of the condition by inocu- 

 lating subcutaneously two guinea-pigs with small 

 portions of the submucous tissue of the caecum of 

 a cow affected with the disease. In neither case was 

 there any reaction at the site of inoculation ; but the 

 animals became considerably thinner, so that in spite 

 of the absence of any local affection, they considered 

 that the animals were suffering from a generalized 

 tuberculosis. About five weeks after the inoculation, 

 however, they were astonished to find that the con- 

 dition of the animals had improved, and at the end of 

 eight weeks both guinea-pigs were again in a perfectly 

 sound condition. As a similar state of affairs may 



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