52 BULLETIN 106, U. S. DEPARTMENT OF AGRICULTURE. 



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. Nor 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 



