506 Diseases of t lie Genital Organs 



The more voluminous data regarding the frequency of 

 observed abortions in herds show a higher rate generally 

 than that recorded in experimental inoculations. The ex- 

 ception is the data submitted by Bang showing but 7 per 

 cent, in cows of the Thurebylille herd. When the data upon 

 heifers in first pregnancy are examined, it is found that 

 under the prevailing conditions in herds the ratio of ob- 

 served abortions (52.55', ) is far in excess of the recorded 

 abortions following experimental inoculations. When cows 

 and heifers are taken together, the observed abortions 

 (19 r ; ) are but 1.08 per cent, below the ratio reported in the 

 experimentally inoculated animals. 



The objection to these data may be urged that they are 

 from "infected" or "badly infected" herds, but no data are 

 available from non-infected herds. One often hears of non- 

 infected herds, but any attempt to get in contact with such 

 and. secure accurate data for record leaves one with the 

 feeling that he has been pursuing a mirage. If there are 

 herds in which no abortions occur and in which each cow or 

 heifer of breeding age produces a healthy calf each twelve 

 months, the failure of those having knowledge of the facts 

 to publish the details serves as an impassable barrier to their 

 use. The question can be judged or decided only upon the 

 available recorded data. 



The further and pertinent objection may be made that in 

 many of the experiments the animals were destroyed prior 

 to the termination of pregnancy and that some or many of 

 these might have aborted had they not been killed. But it 

 would be equally erroneous to pick out from the total those 

 animals kept until after termination of pregnancy and ac- 

 cept the results in this group alone. The probability of 

 abortion decreases as the duration of pregnancy advances : 

 the disease may be present and severe but may result in 

 premature birth, in retained afterbirth, or in calf scours or 

 pneumonia. 



On the other hand, it may be very properly maintained 

 that the animals slaughtered prior to the termination of 

 pregnancy were generally held beyond the alleged "period 



