POSITION OF THE BACILLI 271 



bacilli, but to use a weaker solution of sulphuric acid, say 5 per 

 cent, in decolorising ; in the case of films and thin sections, 

 decolorising with such a solution for fifteen seconds is usually 

 sufficient. Thereafter the tissues are coloured by a contrast 

 stain, such as a watery solution of methylene-blue (vide p. 101). 

 The bacilli are also readily stained by Gram's method. Regarding 

 the presence of spores practically nothing is known, though some 



FIG. 93. High -power view of portion of leprous nodule showing the 

 arrangement of the bacilli within the cells of the granulation tissue. 



Paraffin section ; stained with carbol-fuchsin and methylene-blue. x 1100. 



of the unstained or stained points may be of this nature. We 

 have, however, no means of testing their powers of resistance. 

 Leprosy bacilli are non-motile. 



Position of the Bacilli. They occur in enormous numbers 

 in the leprous lesions, especially in the tubercular form. In fact, 

 so numerous are they that the granulation tissue in sections, 

 properly stained as above, presents quite a red colour under a low 

 power of the microscope. The bacilli occur for the most part 

 within the protoplasm of the round cells of the granulation tissue, 

 and are often so numerous that the structure of the cells is quite 



