Infections of the Ovum, Embryo and Fetus 525 



the fifth to eighth month of pregnancy. Prior to concep- 

 tion, probably three to six months had elapsed since the 

 previous calving. She is consequently nearly or completely 

 dry and the owner cannot hope for profitable lactation or 

 for a healthy calf until about twelve more months have 

 elapsed. Naturally she is sold for beef, or disappears for 

 some other reason. This is well illustrated in the work of 

 Bland 1 , who states that in the herds listed in 1914-1916, to- 

 talling 1,016 animals, there had been, in 1919, 305 or 

 30 per cent, of abortions. In the same herds, in 1914- 

 1916, 160 animals are accounted for which had aborted in 

 1913; 145, or 48 per cent., of those aborting in 1913 were 

 not in the herds in 1914. Probably some died, some were 

 sterile and therefore sold, and some may have conceived 

 and have been sold to other dairymen but not because the 

 seller thought them immune to abortion. Of the 160 cows 

 aborting in 1913 which are reported in 1914-1916, 107, or 

 67 per cent., calved and 33 per cent, failed to produce calves 

 during the period of two or three years between 1913 and 

 1916. Though they were presumably the most promising 

 of the aborters in 1913, 33 per cent, failed to produce calves. 

 These data fail to show a valuable immunity. 



Infections of the genital tract, like chronic infections of 

 other organs, are rarely static. During the interval between 

 weaning (or changing from a milk to a vegetable diet) and 

 the first coitus, the animal enjoys the most healthful period 

 of its life, judged by clinical standards. When sex activity 

 begins, it is difficult to conceive of a static condition of the 

 bacteria in the genital tract. Abortion signifies one grade 

 of activity of these bacteria, lower in virulence than sterility 

 and higher than dysentery and retained fetal membranes. 

 It should not be expected that in each breeding year an 

 active, virile infection would maintain throughout a given 

 level but that it would vacillate from year to year. Should 

 the intensity increase markedly, causing hydrosalpinx, pyo- 

 salpinx, or ordinary salpingitis, the animal becomes seri- 



1 Bland, G. R., Second Rep. Ag. Organizer, Epizootic Abortion Exp., 

 1911-1916, Oxfordshire, Eng., page 15. 



