624 PATHOGENIC MICROORGANISMS 



be true can not, at present, be decided. As a source of infection, how- 

 ever, 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, 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 bacilli in 

 dust, soil, etc., must always be looked upon with suspicion, 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, 17 

 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 inability 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, 

 nevertheless, some evidence which points toward the production of a 

 poisonous substance of some kind by the bacillus. Rost, 18 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 "leprolin," and which he employed therapeutically in the same 

 manner in which tuberculin is employed in tuberculosis. As stated be- 

 fore 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 



17 Arning, Vers. <1. Naturfor. u. Aerzte, 1886. 



18 Kost, loc. cit. 



