CHAPTER XXIX 



THE ACID PAST GROUP— THE GENUS MYCOBACTEEIUM— 

 TUBERCULOSIS, PARATUBERCULAR DYSENTERY AND 

 LEPROSY. 



The organisms belonging to this group are all slender, 

 nonsporing rods, which do not generally produce capsules, 

 are Gram-positive, and nonmotile. They also have in com- 

 mon the character of acid fastness, that is, they are rela- 

 tively difficult to stain with the aniline dyes, but when once 

 stained they retain the stain with avidity, not losing it even 

 in the presence of relatively strong solutions of mineral 

 acids. All of the species belonging to this group, further- 

 more, show a decided tendency under certain cultural con- 

 ditions to produce elongated, more or less branched threads. 

 In some respects they are intermediate' between forms like 

 Actinomyces and the other bacteria. 



Organisms belonging to this group are widely distributed 

 in nature, in soil, in manure, etc. Three species are of 

 importance because of their ability to produce disease, that 

 is, they are primarily pathogenic and parasitic. These are 

 the Mycobacterium tuberculosis, the cause of the disease 

 tuberculosis, Mycobacterium paratuberculosis, the cause of 

 paratubercular dysentery in cattle, and Mycobacterium 

 leprce, the cause of leprosy in man. 



Mycobacterium tuberculosis 



Synonyms. — Bacillus tuberculosis, Bacterium tubercu- 

 losis. 



This organism, together with its several varieties, is the 

 specific cause of tuberculosis in man, birds and various 



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