52 



The internal organs are relatively slightly affected in the natural 

 disease. Small foci have been found in the hver by Dean (4) and 

 in the liver and spleen by McCoy (10). Wherry (7) reports finding 

 the bacilli in smears from both the liver and spleen. The writer has 

 found microscopic lesions containing the characteristic bacilli in the 

 liver ia a case of the experimental disease. 



Lesions have been observed in the bone marrow by Dean (4), and 

 the same author states that the nerves are invaded by the bacilli of 

 the disease. McCoy (10) found the bacilli in the urinary bladder in 

 one case. 



With a disease showing such a striking similarity to human leprosy, 

 attention has naturally been directed to the bacteriological examina- 

 tion of the nasal mucus. Dean (4) and Wherry (7) have both 

 found the characteristic bacilli in the nasal mucus, while McCoy (10) 

 has failed to do so. The writer's experience has been confined to 

 the experimental disease, and in his animals the nasal examinations 

 have been negative. 



ETIOLOGY. 



The accepted etiological factor in the disease is an acid-fast bacillus 

 3 to 5 microns in length and 0.5 micron wide. The bacilli resemble 

 very closely the lepra bacillus of man, but seem to have somewhat 

 greater power to hold carbol-fuchsin stain against mineral acids. 

 The bacilli often have rounded ends and may be curved. The 

 beaded appearance so often seen in lepra bacilli is common. The 

 bacilli show the same tendency to form bundles that is such a marked 

 characteristic of Bacillus leprse. To one familiar with the microscopic 

 appearance of smears from the discharges and lesions of human 

 leprosy the picture presented by similar preparations from the dis- 

 ease of the rat is m9st striking. 



The organism does not grow on the usual culture media — Stefansky 

 (1), Eabinowitch (2), Dean (4),- Tidswell (5) — or on certain special 

 media — Dean (4). 



The organism is not pathogenic for the guinea pigs — Dean (4), 

 Tidswell (5) — rabbit, mouse, monkey — Dean (4). The disease can 

 be transmitted to black and white rats — Dean (4), Wherry. 



SUMMARY. 



In the leprosy-like disease of rats we have an affection which 

 closely resembles, both in its etiological factor and in its pathology, 

 the disease leprosy in man. The fact that the disease is readily 

 propagated in a laboratory animal permits of its investigation in any 

 laboratory. It is earnestly hoped that the study of this disease wiU 

 be taken up by bacteriologists and pathologists, as in this way valu- 

 able information may be gained which will be applicable to the prob- 

 lems presented by leprosy in man 



