Infections of the Ovum, Embryo and Fetus 487 



turbances which commonly destroy the value of the patient 

 for other purposes. 



D. Emphysema of the Fetus 



As a rule the bacteria which infest the utero-chorionic 

 space of the pregnant cow, and which tend to invade the 

 fetus and destroy its life, do not form gases. Instead they 

 most frequently cause a dry necrosis (necrosis of the tips 

 of the embryonic sac) or induce maceration of the fetus. 

 The rapid multiplication of gases within the sealed uterine 

 cavity or the contained fetus is virtually incompatible with 

 the life of the mother unless the cervical canal is open and 

 establishes a free vent for the gases. Usually the crisis of 

 uterine rupture is not reached because the patient succumbs 

 to sepsis. 



Emphysema of the fetus occurs in all species of animals, 

 usually near, or at the end of the normal duration of preg- 

 nancy. The emphysema is apparently the result of second- 

 ary invasion of a recent date. The life of the fetus has or- 

 dinarily been destroyed and the uterine seal broken down by 

 other invaders, preparing an open way for the entrance of 

 the gas producers. When the fetus is emphysematous, the 

 cervical canal is ordinarily open but not dilated. Some- 

 times, as in cases of torsion of the uterus with emphysema 

 of the fetus, the cervical canal is mechanically closed by the 

 torsion. The mechanical injury to the cervix destroys its 

 resistance to invasion, and emphysema results. Sometimes 

 under these conditions the emphysema becomes so great 

 that the fetus occupies almost the entire abdominal cavity 

 and rupture of the uterus appears to be averted chiefly by 

 the support afforded by the contiguous abdominal walls. 



The clinical symptoms of fetal emphysema are essentially 

 those of the uterine gangrene of pregnancy already de- 

 scribed. 



E. The Observed Expulsion of the Fetal Cadaver. Abortion 

 The term "abortion" has a great variety of meanings. In 

 veterinary medicine it ordinarily means the observed expul- 

 sion of a fetal cadaver. If it is stated that twenty per cent. 



