Contagious or Epizootic Abortion in Cows. 
95 
The role of the bull in the transmission of the disease has 
next to be considered. Many persons of experience believe 
that bulls play an important part in spreading contagious 
abortion from cow to cow, their opinion being that by successive 
acts of copulation the abortion bacilli are mechanically trans- 
ferred from the genital passages of diseased to those of healthy 
cows. It is impossible to deny that this is one of the natural 
methods of infection, and facts which have only recently 
been proved will probably be held by many to constitute 
further strong evidence in support of the view that the bull is 
a serious factor in the spread of the disease. The facts here 
referred to are (1) that bulls can be experimentally infected by 
introducing abortion bacilli into the sheath, and (2) that in 
infected herds bulls can sometimes be proved to have contracted 
the disease. The proof of infection in both these cases has been 
furnished by the agglutination test. It would, however, be 
easy to exaggerate the importance of these discoveries, for it 
does not follow from the mere fact that a bull has become 
infected that he would be capable of transmitting the disease in 
the act of service, nor does it follow that he himself became 
infected in that way, since the disease has been detected in 
young animals of both sexes, which had never copulated. It 
must be left to future observation and experiments to furnish 
more conclusive evidence than exists at present regarding the 
relative frequency of infection from the bull, but it seems 
probable that this method has far less importance than infection 
by the mouth. 
The results of infection with abortion bacilli . — The act of 
abortion or premature labour is only a symptom — and an 
inconstant one — of the disease which is caused by the abortion 
bacillus. The cause of the abortion is a diseased condition of 
the womb, and the membranes which surround the foetus, and 
beyond this the post-mortem examination of an infected preg- 
nant cow never reveals anything abnormal. The absence of 
disease from the other internal organs explains the fact that in 
cases of contagious abortion the animal’s general health, at 
least up to the time of abortion, appears quite unaffected. 
After the act of abortion the cow’s health may suffer, but that is 
practically always attributable to retention of part of the 
cleansing, which must be regarded as a complication of the 
original disease. Contagious abortion has been defined as a 
specific uterine catarrh, and no doubt that is accurate for the 
disease as it affects pregnant animals. Obviously, however, the 
definition is not wide enough to embrace all the cases, since 
male animals can contract the disease, and young female 
animals when infected do not develop any catarrh of the 
womb. Indeed, in these animals the post-mortem examination 
