Infections of the Ovum, Embryo and Fetus 505 



The 21 cows used for experimental inoculation show the 

 largest ratio (52.4 ( /r) of observed abortion. Of the 11 

 aborters, however, 4 (Bland, 2; Moore, 2) are known to 

 have aborted, and 2 (Moore) were sterile or aborted unseen 

 the prior year. Only 1 of those aborting (Moore) is known 

 to have calved the previous year and 1 (Bang) may have 

 done so. Omitting the 4 known aborters and the 2 sterile 

 cows of the previous year, there remain 15 cows which pos- 

 sibly calved the prior year, and of these, 5 (23.8% ) aborted. 

 No controls were kept and the ratio is not sufficiently high 

 to constitute good evidence. It is not known that each of the 

 cows did not, when the inoculation was made, carry in the 

 utero-chorionic cavity an infection capable of causing abor- 

 tion. In the one Moore cow, in the group of 5, this is not 

 merely a possibility but a definite probability, since she 

 came from the same herd as the other 4, none of which 

 calved the previous year. 



A study of the available records of experimental inocula- 

 tion in heifers, of which it has been possible to assemble 48, 

 shows that 10 (20.8^ ) are recorded as having aborted. I 

 find only one heifer recorded as having been kept directly 

 as a control — that in my experiment (IX) — and that one 

 aborted. A single case can not be accepted as conclusive 

 nor as valuable evidence, but there is no other way of stat- 

 ing the recorded fact. The question of controls has been 

 ignored. 



The heifers in the Bland experiments (V) were not in- 

 oculated to cause, but to prevent abortion. The inoculation 

 occurred through error. The heifers were assumed to be 

 non-pregnant at the date of inoculation, but later proved to 

 be pregnant. These are inserted in the table under the as- 

 sumption that the effect was the same whether the inocula- 

 tion was made to cause or to prevent abortion. The virtual 

 controls of Bland — (12), (13) — should be applicable, as 

 they were definitely used as controls in efforts to prevent 

 abortion by vaccination of non-pregnant cattle with living 

 bacilli. 



