498 Diseases of the Genital Organs 



tion than the normal single fetus, not because bovine (or 

 equine) twins are unnatural but because the increased 

 drain upon the nutritive supply of the mother lovs^ers her 

 resistance and permits the intra-uterine infection to multi- 

 ply disastrously. 



However important food and environment may be to re- 

 production, so far as known, bacterial invasion of the utero- 

 chorionic space of the cow is absolutely essential to abor- 

 tion, retained afterbirth, and 99 per cent, of sterility. 



(e) The biology of abortion. It is now generally con- 

 ceded technically, though largely denied practically, that 

 abortion may be caused by an unknown variety of bacteria. 

 Any microorganism which may exist within the pregnant 

 uterus, and which is capable of causing metritis and the 

 death of the fetus, may cause abortion. Chronologically the 

 chief infections which have been alleged to cause an im- 

 portant amount of abortion in cows are as follows : 



(1) The micrococcus and short bacillus of Nocard.^ In his 

 researches Nocard recognized a short bacillus (probably 

 paracolon or paratyphus) and a micrococcus in the utero- 

 chorionic space of aborting cows, and in the digestive tube 

 of the abort. He concluded that one or both organisms 

 found were the cause of abortion in the cases investigated 

 by him. He believed that abortion was primarily a disease 

 of the fetus, but that the infection was derived from the 

 uterus. He further expressed the very important view that, 

 if the invaders failed to kill the fetus, they persisted in the 

 individual through birth into extra-uterine life and consti- 

 tuted the basic cause of dysentery in young calves, thus as- 

 serting his belief in the continuity of infection between 

 intra- and extra-uterine life. The views of Nocard were 

 virtually discarded. Something more striking was being 

 sought and demanded. Lehnert, in 1878, and Brauer, in 

 1880, believed that they had promptly and reliably induced 

 abortion by experimental infection. In England, also, 

 Woodhead, Aitken, McFadyean, Campbell and others as- 

 lE. Nocard. Avortement epizootique des Vaches. Rec. de Med. 

 Vet., Vol. Ill, p. 669. 



