the milk of infected mothers. In such instances the infection may remain
dormant until the colt develops and becomes pregnant, when the organism,
finding a condition suitable for its development, produces the disease.

On the other hand, stallions used in covering infected mares may be
carriers of the germs, and when used for the breeding of healthy animals
may in this manner readily transmit the disease to them.

_Diagnosis._--Contagious abortion may be diagnosed by the changes which
occur in the fetal membranes, and also in the expelled feces. In order,
however, to substantiate a diagnosis with certainty, demonstration of
the germ by microscopical examination is necessary. The occurrence of
frequent abortions among the mares in a stable is also an additional
evidence of the contagious character of the malady. It must be
considered that at times infected mares may carry the fetus to full
maturity, in which case the diagnosis is possible only by blood
examinations in a laboratory.

Infected animals usually abort only once; however, in a certain
proportion of cases they may abort even two, three, or four times in
succession.

Animals which establish a tolerance for the infection, and carry the
fetus to full maturity, may nevertheless remain a source of danger for
spreading the disease.

The tests used in laboratories for the diagnosis are the agglutination
and complement-fixation tests, by which the disease may be diagnosed
from a sample of blood from a suspected animal. Such tests, however,
have to be confined to the laboratories, which are equipped for such
work.

_Treatment and prevention._--Medicinal treatment is usually of no avail,
and all efforts should be directed toward the prevention of the
disease. Various medicinal agents have been recommended and are being
exploited for the treatment, but to the present time no satisfactory
evidence has been established as to their merits. Bacterial vaccines
prepared from the specific organism have been given limited trials, but
to date they can not be considered as entirely satisfactory, since it
will require considerable experience with them before their usefulness
can be definitely established.

The prevention should consist largely in sanitary measures directed
toward the disinfection of premises and animals. (For a method for
disinfection of premises see article under that heading.)

The following procedure is advised for the disinfection of animals: To
preven