Contagious or Epizootic Abortion in Cows. 93 
natural cases of the disease are very rarely observed in these 
animals. 
It was until recently very generally believed that contagious 
abortion was exclusively a disease of pregnant cows, although, 
as was first pointed out by Bang, some local inflammation 
follows the injection of large numbers of the bacilli under the 
skin in male animals as well as in females. It has, however, 
now to be recognised that the abortion bacillus may infect 
bovine animals of either sex and any age. This is a fact which 
could probably never have been determined by observation, 
owing to the circumstance that unless the animal happens to 
be pregnant infection with the abortion bacillus is not mani- 
fested by any symptom of disturbance or illness. The fact 
that the disease which is now being considered is not confined 
to pregnant cows has been ascertained by means of the agglu- 
tination test, and it is important to note that what has been 
proved is not merely that cattle of either sex and any age 
can be experimentally infected, but that non-pregnant females 
and bulls do actually contract the disease naturally, viz., by 
contagion or infection. 
Source of the bacilli which cause infection . — It is obviously 
important to know from what source the bacilli which infect 
previously healthy animals come, and the first point to be 
considered in that connection is whether abortion bacilli can 
grow in water, soil, &c., or whether they multiply only in the 
bodies of infected animals. In the first of these alternatives 
a case of abortion might arise almost anywhere, and quite 
independently of any antecedent case of the disease. It is, 
of course, impossible to prove that abortion bacilli never 
multiply outside the bodies of infected animals, but it may 
safely be said that there is no evidence that they do so in 
natural circumstances, and that there is no experience which 
really contradicts the view that the disease with which we are 
dealing is a purely contagious or infectious one. 
The question of the source of the bacilli which cause 
infection is therefore narrowed down to a consideration of the 
channels by which the bacilli leave the body of a diseased 
animal. It is a matter of certainty that the greatest number 
of bacilli escape from the infected animal at the time of 
abortion or parturition and during the next following few 
days, and it has very generally been assumed that the disease 
is mainly spread by the bacilli thus voided. It must he 
admitted, however, that there is at present little or no real 
knowledge regarding the importance of other channels by 
which bacilli might escape from an infected animal. They 
are apparently sometimes passed out with the milk, but 
nothing is known as to their possible presence in faeces or 
