Infections of the Ovum, Embryo arid Feins 



529 



per cent, of the ideal of one calf each twelve months. Dur- 

 ing the same period the reproduction in the controls was 

 77.4 per cent., or only 8.6 lower than in the vaccinated. In- 

 advertently selecting the controls improperly might very 

 well have made a much greater difference. 



Bland compares the abortion rate in 1910 with the rate 

 upon the same premises in 1911-1913, but the cattle in the 

 herds of 1910 were not the same as those used in the experi- 

 ments. In effect, he says, "In 1910 the cow, Rose, aborted 

 (100 per cent, abortion) and in 1911-1914 the cow, Cherry, 

 was vaccinated and calved (100 per cent, calves) ; therefore 

 vaccination reduced the abortion rate from 100 per cent, to 



Fig. 176 — Chart of Agglutination Test on Three Heifers after Inocu- 

 lation with B. abortus with failure to react on date of Abortion. 



zero." That is, Bland asserts that in 1910, 28.9 per cent, of 

 671 animals, or 194, aborted, and later he states that 66 of 

 the 1910 aborters were used in the 1911-1913 experiments, 

 and 128 aborters disappeared. Forty-three cows which 

 aborted in 1910 were vaccinated in 1911-1914, and of these 

 29 (67 per cent.) calved. Evidently the dairymen selected 

 for holding those aborters which gave the greatest promise 



34 



