37

This appearance is never seen in the blood-stream
where the bacilli are found singly or at most in pairs.

In the tissues of the body when seen in section the
bacilli are arranged in irregular clumps.

Each bacillus is surrounded by a mucoid cortex. In
old cultures, peculiar involution forms develop, oval,
club-shaped, spindle-shaped and spherical being common.

This change is especially well seen in dried-up agar
cultures.

The bacillus shows only very slight or no movement.

                           Staining reactions.

With all stains the bacillus stains better at the ends
than in the centre, thus coming under the Pasteurella class
of organism. It stains very easily with watery solutions
of the Aniline dyes.

Lœffler's alkaline Methylene Blue stains deeply in one
minute.

Aqueous Methylene Blue 1 per cent. stains faintly in
one minute.

Ziehl's carbol-fuchsin stains at once and the bipolar
staining is very well shown.

It does not stain by Gram's method or with Weigert's
modification.

By Claudius' method the result is very deep-staining,—
too deep to show the bipolar appearance, for the centre part
is also stained.

Leishman and Giemsa stains give good results—Bacilli
from cultures do not show the bipolar staining so well as
those from the body.

No staining methods have yet shown capsule or spore
formation.

                           III.—BIOLOGY.

                                  Vitality.

The bacillus when outside the animal body has only
very feeble powers of resistance.

It is destroyed immediately by the ordinary strengths
of disinfectants.