PATHOLOGY OF PREGNANCY AND PARTURITION 433 



In human beings the term miscarriage is used when the 

 foetus is not viable and is expelled before the twenty-eighth 

 week ; the term premature birth is used when the foetus is 

 between the twenty-eighth and thirty-eighth week and is cap- 

 able of survival. The viability of the foetus in domestic animals 

 must be the ground for diagnosing premature birth. 



(b) Pathological Complications of Parturition. 



Among savage people the causes preventing birth are 

 reckoned to be weak pains, bad position or want of activity of the 

 foetus, and disproportion between the size of the child and the 

 mother's genital canal, and magic. This latter, and also the 

 want of activity on the part of the foetus, are childishly simple 

 ideas, but with these exceptions the views of savage nations are 

 very close to the reality, especially in the entire absence of 

 external aid. 



The circumstances hindering birth in civilised people are 

 known to be abnormal size of the foetus, or of one of its parts ; 

 abnormalities in the membranes, umbilical cord or placenta ; 

 anomalies in the uterus or external genitals ; faulty position 

 of the foetus ; contracted pelvis, and, after delivery, retained 

 placenta. 



Abnormal size of the foetus may hinder parturition both in 

 human beings and in our domestic animals. The abnormality 

 may affect the whole body or only one part. The belly may be 

 excessively large owing to ascites, or the head may be enlarged 

 by hydrocephalus, which in both cases is often a hindrance to 

 birth. But apart from any collection of fluid in the brain, the 

 child's head may have a disproportionately large circumference. 

 In man this may occur in the children of fathers whose heads 

 are very large, and in calves and puppies under similar circum- 

 stances. 



Deformities and tumours, both in human and animal foetuses, 

 and curvatures and contractures in the latter, may form a more 

 or less complete obstacle to delivery. 



In the vast majority of cases, only one foetus is developed in 

 the human uterus. The simultaneous presence of more than 

 one foetus in the uterus, besides causing increased trouble during 

 pregnancy, interferes with parturition, as abnormal positions of 



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