526 Diseases of the Genital Organs 



ously or hopelessly sterile and her breeding career is closed. 

 This alone renders it impossible for many aborters to abort 

 again the following year. But the cow may improve, the 

 uterus gain new vigor, and the infection become largely re- 

 pressed. Then, if she aborts at all, it will be later in her 

 pregnancy. If the repression of the infection goes further, 

 pregnancy may continue to full term and a live calf be born. 

 The cow may have retained fetal membranes and the calf 

 may have dysentery, but abortion, as defined, is absent. 

 The same or a kindred infection, however, is still present 

 and active. Naturally, therefore, the infection in the geni- 

 tal tract does not as a rule bring about each year precisely 

 the same result, except when hopeless sterility has been 

 reached. 



In all data I have been able to obtain, it has been shown 

 clearly that a given number of cows or heifers which 

 aborted the previous year are more likely to abort again the 

 next year than an equal number of animals which have 

 dropped healthy calves. But the question is to be decided 

 by the percentage of abortions among those which become 

 pregnant. A far larger proportion of the aborters fail to 

 breed. The difference between the two classes is rendered 

 more clear when the false measure of abortion is discarded 

 and the results are measured by the percentage of healthy 

 calves born. 



Regardless of the foregoing facts, it is attempted to con- 

 trol or eradicate abortion, working upon the theory that it 

 is a specific contagious disease and that one attack produces 

 a distinct and valuable immunity. 



B. abortus serum has been proposed as a remedy and has 

 failed. I used serum experimentally upon a group of 26 

 heifers' without result upon abortion, sterility or other in- 

 terference with reproduction. The animals upon which the 

 serum was used aborted at virtually the same rate as the 

 controls and the two groups aborted at the average rate for 

 the herd in which the abortion rate had for years been vir- 

 tually static. My results were in harmony with all available 



'An. Rep. N. v. State Vet. Col., ^16-1917. 



