Infections of the Ovum, Embryo and Fetus 507 



of incubation" of the abortion infection and should mostly, 

 according to the constructive standards of various experi- 

 menters, have aborted prior to slaughter if they were to 

 abort. 



Some investigators have also argued that the finding of 

 the B. abortus in the uterine cavity of the killed animal is 

 experimental proof that it is the cause of abortion. If that 

 is true of the B. abortus, then it must be equally true of all 

 the other microparasites found in the uteri of pregnant 

 cows. It can be experimentally proven that a given organ- 

 ism causes a cow to abort only by those cases which actually 

 abort. It is not necessary to produce infection of the utero- 

 chorionic space in a pregnant cow to show that the B. 

 abortus is capable of causing such infection ; Bang proved 

 that in the first cow in which he recognized the bacillus. 

 If it existed and multiplied in that cow, it follows, a priori, 

 that, implanted in another pregnant uterus of identical 

 species and power -of resistance, it would cause infection 

 again. 



It has been attempted to apply to abortion the postulates 

 of Koch who assumed as a basis for experimentally proving 

 the specific character of a bacillus: (1) The organism 

 needs to be obtained in pure cultures. (2) Inoculation of a 

 sound animal with pure cultures must cause the typical 

 symptoms and lesions observed in naturally infected ani- 

 mals. (3) Pure cultures of the organism must be recov- 

 ered from the tissues of the experimentally inoculated and 

 diseased animal. Koch's postulates are inapplicable to 

 abortion in cattle because the abortion is not the disease nor 

 is it a lesion ; it is merely one of the possible occurrences in 

 the course of a disease having the power to destroy the life 

 of a fetus and to irritate the pregnant uterus in a manner 

 to cause it to expel the fetus. While the data submitted 

 fail to justify the dictum of Bang and others that the inocu- 

 lation of a pregnant cow or heifer with the Bang organism 

 will cause her to abort during the existing pregnancy and 

 thus prove that the B. abortus is the specific cause of abor- 

 tion in cattle, it is not proof that such inoculation is without 



