Contagious or Epizootic Abortion in Cows. 101 
Prevention— The consideration of this part of the subject 
falls naturally into two parts, viz., (1) the means by which a 
healthy herd may be kept free from contagious abortion, and 
the measures which may be employed to eradicate the 
disease from an infected herd. 
1*. There is no doubt that the usual cause of an outbreak of 
abortion in a previously healthy herd is the introduction of 
an infected animal. In the great majority of cases the animal 
which thus serves as the starting point of an outbreak is a cow 
or heifer, but facts already mentioned indicate that it may 
sometimes be a bull. Except when there is perfectly trustworthy 
evidence that a newly purchased animarcomes from a healthy 
herd there is only one practicable safeguard against the possible 
introduction of infection, viz., to keep the animal isolated until 
the agglutination test has freed it from suspicion. Inasmuch 
as a certain time must elapse after infection before a positive 
reaction to this test can be obtained, it is advisable to delay the 
test for three or four weeks after purchase. This may appear 
a troublesome procedure, and in dairy herds in which sales and 
purchases are frequent it can hardly be considered practicable. 
In breeding herds, however, and especially in valuable pedigree 
herds, the trouble and expense of such precautionary measures 
can hardly be pronounced out of keeping with the risk of 
incurring the serious losses which an outbreak of .contagious 
abortion always entails. 
2. To eradicate contagious abortion from a herd is a problem 
of much greater difficulty. It must be stated, in the first place, 
that there is no satisfactory evidence that the disease can be 
either cured or prevented by the administration of any drug 
whatsoever. The alleged success of treatment with carbolic 
acid reposes on a very obvious fallacy, viz., that the disappear- 
ance of the disease from a herd which has been treated in this 
way cannot have been due to natural causes. It has long been 
known that under certain circumstances contagious abortion 
often disappears without any treatment whatever, and the fact 
can be most reasonably explained by assuming that, speaking 
metaphorically, the fire has died out from lack of fresh fuel. 
Although, unfortunately, there are a good many exceptions to 
the rule, cows that become infected while pregnant generally 
make a complete natural recovery after the act of abortion 
or parturition, and are for a time thereafter immune against 
re-infection. Hence the disease tends to die out in a few years 
provided no fresh animals are introduced into the herd. A 
fact which is quite in harmony with this -view is that after one 
or two bad seasons of abortion the further cases are mainly or 
entirely among heifers carrying their first calves. 
For a good many years past the preventive measures 
