474 Veterinary Obstetrics 



micro-organism of the disease itself may pass through the pla- 

 cental capillaries and gain entrance into the fetal circulation, 

 thus accomplishing its destruction. 



So far as known at present, the micro-organisms of those in- 

 fectious diseases which frequently cause abortion in the preg- 

 nant female largely belong to the assumed ultra-microscopic 

 group. The causative agent can pass through an ordinary filter 

 and perhaps also through the dividing membrane between the 

 placental blood-streams of mother and fetus. Among the dis- 

 eases mentioned as causing- abortion, dourine constitutes an ap- 

 parent exception, the disease being clearly due to the presence 

 of a trypanosome. But we do not know that it causes abortion. 

 It prevents breeding certainly enough, but whether it inhibits 

 fertilization in the affected mares or later destroys the young em- 

 bryo is not ascertained. Even in the latter case the parasite ea- 

 ters by the genital canal, is known to exist in the genital secre- 

 tions and can directly attack the fetal membranes. 



The symptoms of abortion from such diseases present no differ- 

 ences from those of accidental abortion and can only be differen- 

 tiated from such by the fact that the abortion occurs in imme- 

 diate connection with the contagious fever itself and independent 

 of any other known influence which could bring it about. 



This form of abortion is important because the loss to the 

 breeder is the same as in other abortions, with the additional 

 danger that, by complicating the disease of the mother, it in- 

 creases the mortality among pregnant females. 



There is nothing to be done in the way of prophylaxis or con- 

 trol of such outbreaks of abortion, aside from the general meas- 

 ures to be taken in reference to the contagious disease of the 

 mother. In this connection it might be well to emphasize what 

 we have already said on page 68 in reference to contagious cel- 

 lulitis, which, because of this tendency to abortion, constitutes 

 one of the most dangerous diseases of stallions and brood mares. 



III. Infectious Abortion. 



The vast majority of abortions in domestic animals are due to 

 infection. The disease is most common in the mare and cow and 

 has been observed in the ewe, goat and sow. 



According to many authors, abortion is most common and 



