BACILLUS OF CHRONIC DYSENTERY IN CATTLE 373 



cent, nitric acid alcohol, then wash in distilled water and counterstain 

 with watery methylene blue. This method stains the lepra bacillus 

 red, while tubercle bacilli are not stained at all. 



Rat Leprosy. There is a disease in wild gray rats which is caused 

 by an acid-fast bacillus and which presents lesions almost identical 

 with those found in human leprosy. The two diseases, however, are 

 not identical. The rat cannot be infected with human leprosy, and 

 there is no reason to believe that the human disease came originally 

 from rats or that man can be infected with rat leprosy. 



Occurrence. Rat leprosy has been observed by Stefansky in Russia, 

 Rabinowitsch in Berlin, Dean in London, Tidswell in Australia, the 

 English Plague Commission in India, and Wherry and McCoy in 

 California; accordingly, it appears to occur over a large territory. 

 Its prevalence bears no relation to human leprosy, as is shown in 

 the Hawaiian Islands, where leprosy among human beings is common 

 and where, in spite of rewards offered, leprosy-infected rats have 

 never been found. 



Pathology. The pathologic lesions of this disease of rats, according 

 to Brincke"rhoff, are as follows : The skin in a well-developed case of 

 the disease presents a patchy alopecia coincident with thickening 

 and nodule formation situated in the subcutaneous tissue. The cut 

 surface of the nodules or thickenings is light yellow in color, clean, 

 dry, and cheese-like. In the region of the nodules the skin is atrophic, 

 and ulcers often form on the prominent parts of the affected area. The 

 subcutaneous fatty tissue is diminished in amount. Histologically the 

 process is seen to be practically confined to the subcutaneous tissue 

 and to consist essentially in the presence of cells rich in protoplasm, 

 with vascular nuclei, whose cell body is more or less completely 

 filled with slender acid-fast bacilli. The subcutaneous fat is replaced 

 by such a tissue. Where the musculature is involved the muscle 

 fibers atrophy and the fibers are infiltrated with the acid-fast bacilli. 

 The peripheral lymph' nodes are generally involved; they are enlarged 

 and on section opaque, pale yellowish-white in color. 



Morphology of Bacillus of Rat Leprosy. It resembles closely the 

 lepra bacillus of man, is 3 to 5 micra long, 0.5 micron wide; it is 

 somewhat more firmly acid-proof than the human lepra bacillus. It 

 often shows a beaded appearance, and presents itself in crowded 

 bundles. The disease can be transmitted by inoculation to gray and 

 white rats. Guinea-pigs and other animals are not susceptible. 



BACILLLUS OF CHRONIC DYSENTERY IN CATTLE (JOHNE'S 



DISEASE). 



Occurrence. There occurs in cattle a chronic dysentery with 

 progressive emaciation and anemia and finally death, due, as it 

 appears, to an acid-fast bacillus which is found in enormous numbers 



