TUBERCULOSIS. LEPROSY 97 



The use of tuberculin did not prove as satisfactory 

 as Koch had expected, and was discontinued almost 

 entirely, except as a means of diagnosis in obscure 

 cases in man and as a test in dairy cows, the latter 

 being practiced extensively in all countries. 



Immunity. — An attack of tuberculosis followed 

 by cure does not render the patient immune, but on 

 the contrary, seems to increase his susceptibiUty to 

 further infections. 



LEPROSY 



Leprosy is a chronic, infectious, endemic disease 

 caused by Bacillus leprce, an organism bearing a very 

 strong resemblance to Bacillus tuberculosis. 



The leprosy bacillus was discovered by Hansen, a 

 Norwegian scientist, in 1872 ; prior to this, certain 

 peculiar cells had been observed in leprous tissue, 

 and Hansen found large numbers of leprosy bacilli 

 lying within these ' ' lepra cells." The leprosy bacillus 

 is a slender rod, usually straight, occurring in charac- 

 teristic bundles; it is without motion, does not form 

 spores, and is usually found in the "lepra cells," al- 

 though sometimes observed in the lymphatic glands 

 and in the blood. 



In the tubercular form the bacilli occur in enor- 

 mous numbers, much greater than in the anaesthetic 

 form. 



