500 Veterinary Obstetrics 



connection with the control of the malady. We know no way 

 to disinfect the pregnant uterus, and if the infection may exist in 

 it for seven months there can be little hope for the prompt 

 eradication of the disease from a herd. 



The Method of Natural Infection doubtless varies greatly 

 in different instances. Consequently one author will place the 

 principal emphasis upon a given method and another upon a dif- 

 ferent avenue of infection. Bang places considerable stress upon 

 infection through the alimentary tract by means of contaminated 

 food. While such a possibility should be recognized, we have 

 little evidence that it plays a highly important part in the major- 

 ity of outbreaks. 



Some writers probably over-emphasize the frequency with which 

 the disease is transmitted by the male breeding animal through 

 copulation. Doubtless this mode of transmission is quite im- 

 portant, and should be fully recognized in all plans for control 

 or eradication. When, however, a cow aborts during the 5th to 

 7th month of gestation," we are skeptical about the correctness of 

 attributing the disease to infection by copulation. If the cow 

 came in estrum during pregnancy, and copulated with the male, 

 we might readily admit that the infection was probably trans- 

 mitted in that way. Bang, in his published researches, makes 

 the period of incubation in experimental cases about 8 to 10 

 weeks and in some rare cases as long as 12 weeks, but when he 

 considers the transmission of the infection by the bull he ap- 

 parently considers the period of incubation as much as 6 or 7 

 months, which seems to us to raise a very serinus question of 

 doubt. If the infection is capable of producing abortion at all, 

 and is introduced by the penis of the male at the time of copula- 

 tion, it would seem more reasonable to expect the bacilli to destroy 

 the life of the fetus at a very early period, or perhaps even the 

 ovum or spermatozoa prior to fertilization, and cause an invisible 

 abortion. We do not believe that copulation constitutes the chief 

 means of transmission nor that we should finally conclude that 

 abortions occurring late during pregnancy are due to this mode 

 of infection. 



Clinical evidence indicates that the disease is most frequently 

 transmitted, either directly or indirectly, through the vulvo- 

 vaginal canal, from a cow which has recently aborted to one 

 which is pregnant. If the disease breaks out in a stable, it tends 



