50 
that the organism is present in the milk of many herds; and that 
vaginal discharges, feces, and milk must contaminate the food of 
almost all cattle, the outlook for the control of abortion becomes 
discouraging, if not hopeless. 
On the other hand, if we accept the original view of Bang that the 
cervical canal is the usual avenue of invasion of the uterus, or adopt 
our own view that it is essentially the sole avenue and that the inva- 
sion must always occur prior to the sealing of the uterus, the outlook 
becomes somewhat more favorable, though still a formidable task. 
The history of attempts to control contagious abortion is every- 
where strewn with disappointment, and has opened a rich field for 
much of the boldest quackery every practiced upon breeders. If our 
views are correct, the presence of an aborting cow amongst pregnant 
cows can have no danger because, if the utero-chorionic space in the 
uteri of the pregnant animals is clean and the uterine seal is normal, 
any infection ehminated by the aborting animal can not reach the 
uterine cavity of a neighboring healthy cow. Common decency, 
however, in the production of milk dictates that aborted fetuses 
should be promptly removed in a sanitary manner and aborters 
having retained placenta or vaginal discharges should be excluded 
from the dairy till healed, and that soiled stalls or gutters should be 
cleaned. 
Repressive laws against contagious abortion in cattle have been 
proposed by various veterinarians, involving compulsory reporting 
of outbreaks, quarantine of infected herds, exclusion of affected 
animals from cattle shows, etc. So far as we know, no such laws have 
ever been put in force. The wide dissemination of the disease, its 
insidiousness, the uncertainty of its diagnosis, and other difficulties 
make the application of such laws impracticable. 
The sale of aborting animals has been largely practiced by some 
breeders and dairymen. It is a wasteful and hopeless process. Our 
data indicate that 25 to 50 per cent of all cows ultimately abort once, 
so that the dispersal process is an economic waste and it fails to check 
abortion. 
It has generally been claimed that one abortion affords a large 
degree of immunity. This is, according to our data, wholly erroneous. 
The idea that one or two abortions should confer immunity against 
future abortions is contrary to reason. It is the live mother and not 
the dead fetus which needs to be immunized. There is no more 
reason why a cow which has aborted shall thereby acquire an immu- 
nity than that one which gives birth prematurely to a calf because 
of the infection of contagious abortion in her uterus should become 
immune, or that a cow suffering from retained placenta from abortion 
infection, although the calf be carried full time and born healthy, 
should be immune. 
