erved, a few days previous to abortion, a sticky, sometimes
purulent, rusty, and odorless discharge. Abortion occurs most frequently
from the third to the seventh month, according to the number of abortions,
occurring early in first abortion, and later in each succeeding abortion
until the calf is carried to full term and the mother has become immune. It
happens frequently that calves are carried almost to full term, and are
born alive, but are sickly, and soon die. Following abortion there is a
dirty, yellowish-gray mucopurulent discharge which persists for two or more
weeks. If abortion occurs early, the fetus is passed surrounded by its
membranes, but if late in the period of pregnancy, the membranes are
retained, decomposition sets in and blood poisoning, which may cause the
death of the animal, or sterility may result.

_Lesions._--The most characteristic change is found in the uterus where a
dark-brown fluid, purulent or even gluey in consistency, and containing
grayish-white flakes separates the material membranes from those of the
fetus, preventing that intimate contact between the two which is so
necessary for the interchange of fluids and gases by which the fetus is
nourished and by which it obtains its oxygen. These being cut off, the
fetus must of course die. The germs producing the disease are found in
greatest numbers at this point. In addition there may be inflammatory
changes, first in the walls of the uterus and then in the tissues of the
fetus. These inflammatory changes seem most intense in the cotyledons and
result in the destruction of the minute structure of those bodies, and they
appear swollen, pale, and soft. The membrane of the uterus between the
cotyledons also may show inflamed and necrotic patches.

_Complications._--Serious results sometimes follow abortion, and this is
particularly the case when there is retained afterbirth. The retained
membranes decompose, the poisonous products of decomposition and the
organisms of decomposition themselves are absorbed, blood poisoning
results, and the animal dies. Sometimes, when the animal is able to resist
the effects of this decomposition, the uterus becomes the seat of such
severe changes that sterility results. The walls of that organ become
thickened and hard, the lining membranes become eroded, and conception can
not take place. At other times the ovaries, where the reproductive cells
originate, become affected and lose their function. Abortion d