622 PATHOGENIC MICROORGANISMS 



minous substances and inoculating with bacteria capable of producing 

 amino-acids from the medium. After leprosy bacilli had been grown 

 on for several generations, they could easily be cultivated on agar slants 

 without special additions or preliminary treatment. 



In spite of extensive work upon this very important problem opin- 

 ions are still divided as to the specific nature of the organisms cul- 

 tivated by Clegg and by Duval. Animal experiments with these cul- 

 tures have remained inconclusive. The cultures after prolonged preser- 

 vation upon artificial media grow heavily, often lose their acid-fast 

 characteristics, develop into strep tothrix-like or diphtheroid forms and 

 become markedly chromogenic, all these characteristics suggesting 

 saprophytism. 



In a recent communication, Duval 13 states his opinion as follows: 

 From 29 cases of leprosy, 22 successive cultivations of acid-fast bacilli 

 were made; in 14 of them a chromogenic organism, similar to that of 

 Clegg, was found. This grows either as a non-acid-fast streptothrix in 

 subsequent cultivations or as non-acid-fast diphtheroid forms. From 

 eight cases an organism distinctly different from the former was cul- 

 tivated which grows only on specific media and by serological tests 

 seems to give reaction which differentiates it from Clegg's organism. 

 Duval believes that there is no reason to assume specific etiological 

 relationship for the first organism mentioned. In the case of the second, 

 he admits that not sufficient proof has been brought, but states his belief 

 that its etiological significance is probable. 



Pathogenicity. Numerous attempts to transmit leprosy to ani- 

 mals by inoculation have been unsuccessful. Nicolle, 14 however, has 

 recently claimed successful experiments upon monkeys (macacus) in 

 whom inoculation with tissue from : nfected human beings was followed, 

 in sixty-two days, by the development of a small nodule at the site of 

 inoculation, in which, upon excision, leprosy bacilli were found. In 

 most cases, however, inoculation has given rise merely to a transient 

 inflammatory reaction. 



Among human beings, leprosy has been a widely spread disease since 

 the beginning of history, and much evidence is found in ancient litera- 

 ture which testifies to a wide distribution of the disease long before the 

 Christian era and throughout the Middle Ages. At the present day, 

 leprosy is most common in the eastern countries, especially in India and 



13 Duval, Jour, of Inf. Dis., xi, 1912. 

 "Nicolle, Sem. medieale, 10, 1905. 



