242 PA THOGENIC BA CTERIA.

covered by Hanseu, and subsequently clearly described
by Neisser.

The bacillus is almost the same size as the tubercle
bacillus—perhaps a little shorter—but lacks the curve
•which is so constant in the latter. 'It stains in very
much the same way as the tubercle bacillus, but permits
of a rather more rapid penetration of the stain, so that

FIG. 65.—Bacillus leprae, seen in a section through a subcutaneous node;
x 500 (Frankel and Pfeiffer).

the ordinary aqueous solutions of the anilin dyes color
it quite readily. It stains well by Grain's method,
by which beautiful tissue specimens can be prepared.
The peculiar property of retaining the color in the
presence of the mineral acids which characterizes the
tubercle bacillus also characterizes the lepra bacillus,
and the methods of Ehrlich, Gabbett, and Unna can be
used for its detection.

Like that of the tubercle bacillus, its protoplasm often
presents open spaces or fractures, which have been re-