RAT LEPROSY 511 



The disease can be transmitted experimentally from rat to rat and 

 probably is transmitted naturally from rat to rat by the agency of 

 fleas (Wherry, McCoy). Although clinically not exactly hke human 

 leprosy the condition is sufficiently like it to arouse much hygienic 

 interest. The distribution of the disease in various parts of the world 

 does not correspond with the distribution of leprosy. A peculiar feature 

 of its distribution is the fact that in San Francisco, as the writer was 

 told by McCoy, almost all the rats that suffered from this disease came 

 from the district in which the retail meat business is located, known as 

 "Butchertown." The organisms were made to multiply in vitro by 

 Zinsser and Cary in plasma preparations of growing rat spleen. Chapin 

 has succeeded in cultivating them by a method analogous to the trypsin- 

 egg albumen method employed by Duval. In the experiments of Zinsser 

 and Cary it was found that although the organisms may retain their 

 acid-fast characteristics for many weeks within leucocytes they degen- 

 erate rapidly within the spleen cells, a fact which seems to have some 

 bearing on the mechanism of resistance possessed by the body against 

 acid-fast organisms. 



