GRANULAR VENEREAL DISEASE AND ABORTION IN CATTLE. 27 



abortion. A cow will be served by the bull and fail to come in heat 

 for two to five periods, convincing the owner that she is pregnant, 

 when unexpectedly she again shows estrum. While such phenomena 

 may depend upon a variety of causes, abortion unquestionably 

 accounts for many of these cases. Occasionally the breeder chances 

 upon the freshly expelled embryo, which may be only 3 to 4 inches 

 long. Since these embryos come away inclosed within the fetal 

 membranes, leaving no afterbirths, the discovery of the abortion is 

 a remote possibility. 



In rare cases the fetus dies from the infection of contagious abor- 

 tion but is not expelled, and the cow or heifer appears sterile. Two 

 things may occur: The fetus may undergo maceration, the tissues 

 break down, some pus escape from the uterus, but largely remain in 

 the organ as pyometra. In other cases the fetus does not break 

 down, but desiccates to form an inert foreign body known as a 

 mummy (lithopaedion). 



When pregnancy nears its close abortion again may escape un- 

 noticed. A fetus may be expelled alive at the eighth month, or even 

 earlier, because of the presence of the infection of contagious abortion 

 in the uterus, and is commonly designated premature birth, though 

 in fact its early expulsion is due to precisely the same cause as that 

 which causes other fetuses to be expelled dead. Or, the infection 

 being present, the fetus may live and develop up to the normal date 

 for parturition, die immediately preceding labor, and be expelled 

 fully developed, fresh, but dead, and it is classed as a stillbirth, 

 though just as evidently an abortion as is the five months' fetus, 

 killed by the same infection. Abortion statistics in any herd can 

 accordingly be merely approximate. 



ABORTION DATA IN HERD A. 



As a basis upon which to build an outline of the behavior of abor- 

 tion in a herd, we submit statistics from herd A in Table 4 below. 

 This herd at first consisted largely of grades, but was later changed 

 into a pedigreed herd. The period covered is 22 years, which serves 

 to afford a fair opportunity for arriving at the average rate of abortion. 

 An average annual rate of 12 per cent of abortions is shown. The 

 vacillations from year to year are exhibited in the diagram, figure 1, 

 and the prevalence of abortion according to age in another diagram, 

 figure 2. During the earlier part of the time covered the herd con- 

 sisted largely of adult cows, which were bought when mature, milked 

 for a time, and sold. Later it has been the policy to grow all heifer 

 calves and breed them. Thus there has been latterly a compara- 

 tively large number of heifers in first or second pregnancy. 



