Infections of the Ovum, Embryo and Fetus 509 



are specific. But the metritis met in essentially all cases of 

 abortion bears no mark by which it can be assigned to any 

 one bacterium. Consequently if several bacteria are pres- 

 ent, there is nothing' in the metritis to indicate which of the 

 invaders is responsible. 



Any contagion competent to injure or destroy an adult 

 may, so far as known, equally imperil the life of an ovum, 

 embryo, or fetus if contact occurs. The vast majority of 

 infections do not and can not reach the intra-uterine young. 

 The opening of the genital tract through the vulva is her- 

 metically sealed at the cervical canal by the uterine seal. It 

 is not known, and there is no reason to suspect, that bacteria 

 can traverse the cervical canal and enter the utero-chorionic 

 space of the pregnant cow while the uterine seal is intact. 

 The mammalian placenta, so long as intact, is not known to 

 permit the passage of any form of pathogenic organism. 

 It has not been shown that any disease-producing organism 

 passes during pregnancy from the blood system of the 

 mother into the utero-chorionic space. Infection is not 

 known to invade the uterine cavity of the pregnant female 

 through the oviducts. There is accordingly no portal of 

 entry into the sealed uterus of pregnancy through which 

 bacteria have been known to enter. The orthodox con- 

 tagious-abortionists positively assert that the B. abortus 

 enters the uterus during pregnancy, but avoid stating by 

 what avenue the invasion occurs. 



I have held that the infections which prevent or interrupt 

 reproduction invade the uterus prior to the sealing of the 

 cervical canal ; either the infection was present in the uterus 

 at the time of coitus, or it was introduced during that act. 



The frequency of abortion in a herd usually corresponds 

 fairly well with the intensity of infection by B. abortus. 

 In those herds where abortion and other interferences with 

 reproduction are common, the agglutination and comple- 

 ment-fixation tests usually show intense infection with B. 

 abortus. But such reactions can only show that the B. 

 abortus is somewhere active (or has been active) and can 

 not show that it caused a given abortion. If such tests 



