DISEASES OF THE GENERATIVE OEGANS. 169 



has failed to receive the support of exjDerimental 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 suscep- 

 tible, but young ones in first or second pregnancy most frequently 

 abort. A second abortion is not unusual, and a third may occasion- 

 ally occur, after which the cow usually becomes immune and there- 

 after 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, de- 

 veloping 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 foot- 

 hold 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 abor- 

 tion 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 mem- 

 branes 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 tlie 

 walls of the uterus and then in the tissues of the fetus. These in- 

 flammatory changes seem most intense in the cotyledons and result 

 in the destruction of the minute structure of those bodies, and thev 

 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 



