52 BULLETIN 106, U. S. DEPAKTMENT OF AGKICULTTJEE. 
Our data show that the immunity following abortion is not the 
immunity ordinarily following recovery from an acute contagious 
malady, but on the contrary is what we may designate age immunity. 
The animal has with age acquired a higher degree of resistance to 
abortion than she enjoyed as a heifer. 
In view of the facts thus far elicited, it is doubly inexpedient to 
fight abortion by selling aborters. If there is truth in the belief that 
an animal from a herd where abortion is virulent may introduce a 
more highly virulent strain of infection into another herd, it is evi- 
dently wrong to sell such animals. The greatest objection to the 
selling plan for the control of abortion is that it causes a serious and 
needless drain upon the herd. As already stated, the resistance to 
abortion increases with age. If an aborter will again breed, she has 
in the meantime aged one year, has acquired increased resistance, 
and is on the whole a safer breeder than the previous year. More- 
over, if properly handled at the time of aborting, as Bang early 
pointed out, the danger from reaborting may be very largely 
eliminated. 
McFadyean and Stockman and others suggest the possibility or 
probability of establishing an efficient immunity through the use of 
biological products (abortins, bacterins), but the investigations in this 
direction have not yet afforded definite results. INTor can we see hope 
that the plan will succeed. Apparently their hopes are predicated 
upon an alleged natural immunity following one or two abortions. 
If our data are correct, the power to control abortion by this means 
is predicated upon our ability to induce an artificial immunity in 
a chronic disease incapable itself of producing natural immunity. 
Sven Wall, Holth, and others have enthusiastically embraced the 
hypothesis that the disease may be controlled by isolating the infected 
animals with the aid of the agglutination, complement-fixation, or 
other laboratory tests, but a glance at their investigations intimates 
that a very large percentage of animals would need to be isolated, a 
large proportion of herds would have to install- the method, and it is 
not yet determined that success would follow. The outlook at present 
is that the isolation would prove well-nigh as great an economic 
burden as the malady. 
Brauer suggested many years ago the hypodermic administration 
of carbolic acid as a preventive for abortion, and many have had 
apparently good results, but there seems to be no great reason for 
accepting the alleged results as more than apparent. 
Much has been claimed for vaginal disinfection of pregnant animals, 
but this plan has not been supported by conclusive evidence. 
Our conclusion that the infection enters the uterine cavity through 
the cervical canal prior to or very soon after conception leads us to 
advise the thorough douching of the vagina for a time before and 
