Natural Infection. 743 



tion of toxins it favors the penetration of other bacteria present in the intestines 

 and other tubular organs or body cavities, into the blood circulation and other 

 organs, thereby indirectly producing abortion. He produced abortion successfully 

 in guinea pigs, rabbits and cows by feeding pure cultures.— Abortion can evidently 

 be occasioned by various infectious causes, since it is quite frequently observed in 

 the course of acute infectious diseases, but such cases should be interpreted dif- 

 ferently than as the independent disease of infectious abortion. 



Natural infection may take place from the external genitals, 

 most frequently it is transmitted during copulation by males, 

 who have previously covered infected females. On the other 

 hand the straw and floors of stables become contaminated with 

 the vaginal discharge during and after abortion, by the amniotic 

 fluid and the fetal membranes, which contain enormous numbers 

 of bacilli, whence the contagion may likewise penetrate the 

 genital organs; at the same time the infection may be intro- 

 duced by various objects, such as sponges and other utensils 

 and also by attendants. 



The possibility of an intestinal infection in cows, goats 

 and sheep, by the ingestion of food and drmking water con- 

 taminated with amniotic fluid and afterbirth, was proven be- 

 yond a doubt by the successful experiments of Bang; and this 

 mode of infection should be considered as the natural infection 

 more often than has heretofore been thp case. Especially does 

 it play an important part in cases where the malady spreads 

 rapidly on a farm. 



In cattle establishments free from the infection the virus is 

 usually introduced by an already infected female, who during 

 abortion infects the stable, and during copulation infects the 

 male. The infection then spreads on this particular farm with 

 every favorable opportunity, since the first cases of abortion 

 or premature births are given little attention, as they are fol- 

 lowed by new cases only after a considerable period, and con- 

 sequently the necessary measures to eradicate the disease are 

 omitted. The introduction of the disease can also be accom- 

 plished by means of animals that suffer from a chronic uterine 

 catarrh subsequent to abortion, and also rarely by animals that 

 in spite of their being infected, carry the fetus the full term. 

 More seldom is the disease introduced by males that have re- 

 cently been covering animals on infected premises, and likewise 

 also by new-born animals from such farms. 



The infection spreads as a rule only among animals of 

 the same species, at times however animals of other species 

 are attacked. As a matter of fact the Bang bacillus is not 

 only capable of producing abortion in cattle, but also in horses, 

 goats and sheep (Garcia & Izcara found during an epizootic 

 abortion among sheep, a bacillus in the exudate which mor- 

 phologically corresponded with Bang's organism) ; on the other 

 hand Ostertag's streptococcus has to the present date been 

 found exclusively in mares. 



