Infections of the Ovum, Embryo and Fetus 489 



vanced rapidly during the eighteenth century. In the nine- 

 teenth century Pasteur and others firmly established the 

 fact that disease is chiefly due to contact and that the under- 

 lying cause is a living microparasite passing from the dis- 

 eased to the healthy animal as a result of direct or indirect 

 contact. 



The belief in the infectiousness of abortion has experi- 

 enced a long and eventful course of development which has 

 not yet been completed. For a time a few abortions were 

 ascribed to infection, but these were at first limited to those 

 cases where ingenuity failed to ascribe any other reason. 

 At present probably a majority of people believe that most 

 abortions are due to infection. The observed expulsion of a 

 fetal cadaver came to be regarded as a disease, and by many 

 is still so designated. Those abortions believed to be due to 

 contact accordingly became known as "contagious," "infec- 

 tious," or "epizootic" abortion and were considered a specific 

 malady. Many believed, and still believe, that, if a cow 

 aborts as a result of infection, it must be due to one infecting 

 agent and one only. 



Mammalian existence is divisible into two clearly defined 

 eras — intra-uterine or ante-natal, and extra-uterine or post- 

 natal life. In post-natal life an indefinite number of infec- 

 tions may threaten health or life. On the other hand, it has 

 been constructively assumed that during intra-uterine life 

 but one bacterium or other microparasite may threaten the 

 unborn animal. It is further assumed for all practical pur- 

 poses that an infection invading the fetus can not cross the 

 birth line and continue as a disease of the calf. Neither has 

 it been commonly assumed that an infection of the pregnant 

 female can invade the fetus within her uterus. Technically 

 all pathologists admit that tuberculosis and syphilis may 

 pass from mother to fetus, but this is not credited with any 

 important bearing upon "contagious abortion." While the 

 existence of such belief may be technically denied by the 

 orthodox contagious-abortionists, they practically teach that 

 "contagious abortion" is due to an infection which acts 

 without contact. That is, if a cow aborts in the presence of 



