Staining 



763 



Etiology. The cause of leprosy is, without doubt, the 

 lepra bacillus, discovered by Hansen in 1879. 



Morphology. The bacillus is about the same size as 

 the tubercle bacillus. Its protoplasm commonly presents 

 open spaces of fractures, giving it a beaded appearance, like 

 the tubercle bacillus. It occurs singly or in irregular groups. 

 There is no characteristic grouping and filaments are un- 

 known. It is not motile and has no flagella and no spores. 



Duval found that the cultivated bacilli are longer, more 

 curved, and show a greater irregularity in the distribution of 

 the chromatin than those in the tissues where they are short, 

 slender, and slightly curved. In artificial cultures there is a 



Fig. 249. Lepra bacilli. Smear from a lepra node stained with carbol- 

 fuchsin (Kolle and Wassermann). 



delicate filamentous arrangement of the bacilli, especially 

 where they have become accustomed to a saprophytic exist- 

 ence. They often contain distinct metachromatic granules 

 analogous to those met with in certain forms of the diphtheria 

 bacillus. They are quite pleomorphous, and in the same cul- 

 ture all forms occur, from solidly staining coccoid shapes to 

 slender slightly curved filaments, with numerous chromatic 

 segments and occasionally metachromatic granules. Some- 

 times the organisms are pointed at the ends. 



Staining. It stains in very much the same way as the 

 tubercle bacillus, but permits of a more ready penetra- 

 tion of the stain, so that the ordinary aqueous solutions 



