Abortion may occasionally be transmitted from cow to cow by direct contact. The discharges from diseased cows, swarming with the germs, soil the external genitals, tail, and hind quarters, and then a susceptible animal, by contact, gets the infective material upon the vulva, the infection traveling up the genital canal and directly infecting the uterus. The belief long entertained that the female acquires the disease at the time of copulation as a result of transference of the infection from affected to healthy females on the genital organs of the bull has failed to receive the support of experimental evidence. The view that the disease is spread to any great degree in this way has been largely discredited. Cows of all ages are more or less susceptible, but young ones in first or second pregnancy most frequently abort. A second abortion is not unusual, and a third may occasionally occur, after which the cow usually becomes immune and thereafter carries her calf to maturity. Heifers from aborting mothers sometimes seem to be less susceptible than others. _Symptoms._--Contagious abortion is a very insidious disease, developing very slowly through several months of the gestation period, and resulting finally in the expulsion of the immature young, this act being simply an indication of the presence of the disease and not the disease itself. Because of this slow development and the fact that the health of the animal is not noticeably influenced, the presence of the disease may not be suspected until it has gained a firm foothold in the herd. The symptoms of approaching abortion are those preceding normal calving. In addition, there may be observed, 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.