_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 does not invariably follow infection, but the calf is carried to full term. In these cases, however, retained afterbirth is a common occurrence, even to the extent that frequent retention of afterbirth in a herd may be taken as an indication of the presence of the disease. Very often suppurative processes persist for a long time, preventing conception, or sterility may result without apparent cause. A sterile cow is valueless, of course, for any purpose except for beef. Such animals are a source of infection for the others and should not be allowed to remain in the herd.