PATHOGENIC BACTERIA. 107 



ing the bacillus on a special serum obtained by injecting calves 

 with the leucocytes of guinea-pigs, has secured a toxin which 

 he used to immunize horses, and the serum so obtained has 

 been tried with encouraging results, but its value is still doubt- 

 ful. 



Examination of Milk for Tubercle Bacilli. Place a drop of 

 the sample on a cover-glass and mix it with 2 drops of a 1 per 

 cent, solution of sodium carbonate. The cover-glass is then 

 gently warmed until evaporation is complete. The saponified 

 fat is then stained as the ordinary cover-glass preparation. 

 Only a very few persons have succeeded in discovering the 

 bacillus in milk. 



Lepra Bacillus. (Hansen.) 



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

 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-Uftreduzzi have obtained growths upon 

 blood serum to which peptone and glycerine had been added, 

 but the accuracy of this observation is very doubtful. 



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. 



Rabbits which had been infected through the anterior chamber 

 of the eye showed the lepra nodules (containing the lepra 

 bacilli) diffused through various organs, but here again the 

 results are not wholly satisfactory. 



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 



