in a section of country
containing a number of glandered animals others can seem to contract and
develop the disease without having apparently been exposed to contagion.

_Causes._--The contagious nature of glanders, in no matter what form it
appears, being to-day definitely demonstrated, we can recognize but one
cause for all cases, and that is contagion by means of the specific
virus of the disease. The causative organism is known as the _Bacillus
mallei_.

In studying the writings of the older authors on glanders, and the works
of those authors who contested the contagious nature of the disease, we
find a large number of predisposing causes assigned as factors in the
development of the malady.

While a virus from a case of glanders if inoculated into an animal of
the genus _Equus_ will inevitably produce the disease, we find a vast
difference in the contagious activity of different cases of glanders. We
find a great variation in the manner and rapidity of the development of
the disease in different individuals and that the contagion is much more
liable to be carried to sound animals under certain circumstances than
it is under others. Only certain species of animals are susceptible of
contracting the disease, and while some of these contract it as a
general constitutional malady, in others it develops as only a local
sore.

In acute glanders the contagion is found in its most virulent form, as
is shown by the inevitable infection of susceptible animals inoculated
with the disease, while the discharge from chronic semilatent glanders
and farcy may at times be inoculated with a negative result; again, in
acute glanders, as we have a free discharge, a much greater quantity of
virus-containing matter is scattered in the neighborhood of an infected
horse to serve as a contagion to others than is found in the small
amount of discharge of the chronic cases.

The chances of contagion are much greater when sound horses, asses, or
mules are placed in the immediate neighborhood of glandered horses,
drink from the same bucket, stand in the next stall, or work in the same
wagon, or are fed from feed boxes or mangers which have been impregnated
by the saliva and soiled by the discharge of sick animals. Transmission
occurs by direct contact of the discharges of a glandered animal with
the tissues of a sound one, either on the exterior, when swallowed mixed
with feed into the digestive tract, or when dried and inhaled as dust.