BACILLUS LEPRAE AND LEPROSY 509 



as the primary path of infection. Whether or not this be true can 

 not, at present, be decided. As a soiu-ce of infection, however, the 

 nasal mucus and, secondarily, the saliva, are certainly the vehicles 

 by which large numbers of the bacilli leave the infected patient, and, 

 therefore, tend to spread the disease. 



The contagiousness of leprosy is far less than is that of most other 

 bacterial diseases. Physicians and others who come into direct contact 

 with large numbers of leprous patients, observing at the same time the 

 ordinary precautions of cleanliness, rarely contract the disease. On 

 the other hand, intimate contact with lepers without such precautions 

 is the only possible means of transmission. The demonstration of 

 leprosy bacilU in dust, soil, etc., must always be looked upon with sus- 

 picion, since, apart from actual human inoculation, there is no method 

 of positively differentiating the bacilli from similar acid-fast organisms. 

 Instances of transmission by contact are on record, not the least famous 

 of which is the case of Father Damien, who contracted the disease while 

 taking care of the lepers upon the island of Molokai. Hansen states 

 that in his knowledge no case of leprosy can be found in which careful 

 examination of the past history will not reveal direct contact with a 

 previous case. Direct inoculation of the human being with material 

 from a leprous patient has been successfully carried out by Arning,^ 

 upon a Hawaiian criminal. In this case a piece of a leprous nodule 

 was planted into the subcutaneous tissue of the left arm. One month 

 after the inoculation, pain appeared in the arm and shoulder, and four 

 and a half months later a typical leprosy nodule was formed. Four 

 years after the inoculation, the patient was a typical leper. 



Although our inabihty to cultivate the leprosy bacillus, and the lack 

 of success attending animal inoculation, have made it impossible to study 

 more closely the toxic action of this microorganism, there is, neverthe- 

 less, some evidence which points toward the production of a poisonous 

 substance of some kind by the bacillus. Rost,^ who claims to have 

 cultivated the bacillus, manufactured from his cultures, by the technique 

 for the production of "Old Tuberculin," a substance which he called 

 "leproUn," and which he employed therapeutically in the same maimer 

 in which tuberculin is employed in tuberculosis. As stated before, the 

 results of Rost still lack confirmation. Of far greater importance, both 

 in demonstrating the probability of the existence of a definite toxin as 

 well as in indicating the close relationship between the leprosy bacillus 



' Aming, Vers. d. Naturfor. u, Aerzte, 1886. * Rost, loc. cit. 



