Pathogenic Bacteria

252 PA THOGENIC BACTERIA.

The most characteristic growth is upon potato. It
first appears in about forty-eight hours as a transparent,
honey-like, yellowish layer, developing only at incuba-
tion-temperature and soon becoming reddish-brown. As
this brown color of the colony develops, the potato for
a considerable distance around it becomes greenish-
brown. (See Frontispiece.} No other known organism
produces the same appearance upon potato.

In litmus milk the growth of the glanders bacillus is
associated with the production of an acid that reddens
the reagent, with the formation of a firm coagulum and
the subsequent separation from it of a clear reddish
whey.

The organism loses its virulence if cultivated for many
generations upon artificial media.

The bacillus is killed in five minutes by exposure to
55° C.

That this bacillus is the cause of glanders there is no
room to doubt. Iv6ffler and Schiitz have succeeded by
the inoculation of horses and asses in producing the
well-known disease.

The organisms when in cultures can be stained with
the watery anilin-dye solutions, but are difficult to stain
in tissues. They do not stain by Gram's method.

The chief difficulty in staining the bacillus in tissues
is the readiness with which it gives up the stain in the
presence of decolorizing agents. Loffler at first accom-
plished the staining by allowing the sections to lie for
some time (five minutes) in the alkaline methylene-blue
solution, then transferring them to a solution of sulphuric
and oxalic acids—

Concentrated sulphuric acid, 2 drops;

5 per cent, oxalic-acid solution, i drop ;

Distilled water, 10 c,cm.

for five seconds, then transferring to absolute alcohol,
xylol, etc. The bacilli appear dark blue upon a paler
ground. This method gives very good results, but has