PATHOGENIC BACTERIA. 99 



it as a cure for tuberculosis. The results are as yet undecided. 



Tuberculin as a diagnostic agent. In cattle it has been used in 

 doses of 30 to 40 -grammes. When they are tubercular severe 

 reactions follow its injection. 



Lepra Bacillus. (Hansen.) 



Origin. In 1880 Armauer Hansen declared, as the result ot 

 many years' investigation, that he found a bacillus in all leprous 

 processes. 



Form. Small slender rods somewhat shorter than tubercle 

 bacilli, otherwise very similar in appearance. 



In the interior of the cell two to three oval spaces are usually 

 seen, not known if spores or otherwise. 



Properties. They are immotile, do not liquefy the nutrient 

 media. 



Growth. Bordoni-Uffreduzzi have obtained growths upon 

 blood serum to which peptone and glycerine had been added. 

 The growth is very slow, requiring about eight days at a tem- 

 perature of 37 C. 



Colonies. Small grayish round spots, under microscope ap- 

 pearing like a close-netted spider web around a firm centre. 



Stab Cultures. Show a waxy -like growth along the needle track. 



Staining. They resist the decolorizing action of acids as the 

 tubercle bacilli, but they are easily stained, requiring but a 

 few minutes with the ordinary watery solutions. They take 

 Gram's stain readily. 



Pathogenesis. Arning has inoculated prisoners with tissue 

 obtained from leprous patients, and produced true leprosy. 



Babbits which had been infected through the anterior chamber 

 of the eye showed the lepra nodules (containing the lepra 

 bacilli) diffused through various organs. 



In man the skin and peripheral nerves are principally affected, 

 but the lymphatic glands, liver, and spleen can also become the 

 seat of the lepra nodules. The lepra cells which compose these 

 nodules contain the bacilli in large numbers. By applying a 

 vesicant to the leprous skin the serum thereby obtained will con- 

 tain great numbers of bacilli. This is a simple diagnostic test. 



Method of Infection. Not yet determined ; the air, soil, water, 

 and food of leprous districts have been carefully examined with- 

 out result. 



