SEC. 3. PAETURITIOK. 



706. Owing to the growth of the foetus, and also to the 

 accumulation of the amniotic fluid, the uterus towards the 

 end of pregnancy has become much distended and has risen 

 into the cavity of the abdomen, displacing the abdominal 

 viscera. The expansion of the uterus during pregnancy is a 

 complex process in which the mechanical effects of the in- 

 creasing internal pressure are mingled with those of growth. 

 Though the uterine walls are, as we have said, much thickened 

 by the addition of new muscular fibres as well as by the 

 increase in length, breadth, and thickness of the individual 

 fibres, and also enlarged by the vascular development, they 

 become somewhat thinned again towards the end of pregnancy 

 by reason of the great distension of the cavity. The Fallopian 

 tubes and the round ligaments share in the uterine enlargement, 

 in so far as their muscular tissue is increased ; but the mucous 

 membrane of the former does not alter, and the only changes 

 taking place in the ovary are those concerned with the corpus 

 luteum left by the shed ovum. The walls of the vagina are 

 congested, soft and hypertrophied. Previous to labour the 

 foetus occupies in the womb a position which it assumes at a 

 quite early date, namely, one in which the head is directed 

 downwards towards the pelvis ; this is at least the normal 

 position, though deviations from it not infrequently occur. 



From an early date waves of contraction, at times rhythmical, 

 sweep over the enlarged uterus and towards the end of preg- 

 nancy become more marked. As a rule these are " insensible " 

 contractions, that is to say the mother is not conscious of them, 

 though at times they may be distinctly felt ; and in all cases 

 they are temporary, producing no permanent effect on the uterus 

 or its contents. Though, as shewn by the cases of premature 

 labour and abortion, whether occurring from natural causes or 

 induced artificially, the uterine muscles are capable at even an 

 early date of carrying out the systematic contractions which 

 lead to the expulsion of the foetus, they do not in normal partu- 

 rition enter upon this phase of activity until a certain time has 



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