CHAPTER VI 



DESCRIPTION OF JOHNE'S BACILLUS— CULTIVATION 



OF THE BACILLUS— NATURE OF THE ** ESSENTIAL 



SUBSTANCE "—DESCRIPTION OF CULTURES 



Description of Johne's Bacillus. — The specific bacillus 

 of pseudo-tuberculous enteritis, commonly known as 

 "Johne's bacillus," belongs to the acid-fast group of 

 bacteria, and is allied to the various tubercle bacilli. 

 According to the classification of micro-organisms 

 adopted by Lehmann and Neumann, it would be more 

 correct to describe it as a mycobacterium, and the 

 scientific name of the micro-organism would then be 

 Mycobacterium enteritidis chronicce pseudoiuberculosce 

 bovis Johne, the name by which we have suggested 

 it should be known. At the same time, in English 

 literature it is usually referred to as "Johne's bacillus," 

 and in Continental countries as the " paratuberkel- 

 bazillus," or bacillus of pseudo-tuberculous enteritis. 

 In the lesions of the disease the bacilli often appear 

 in extremely large numbers. They are present as 

 slender rods, sometimes slightly bent, and are usually 

 between i and 2 a* in length. Sometimes they show a 

 beaded appearance, but this is not so marked as in 

 the tubercle bacilli. Their size and appearance are 

 such that it is not possible to detect any pecuHarity by 

 which they can with certainty be differentiated from 

 tubercle bacilli (see Plate V.). 



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