SEC. 3. PARTURITION. 



965. 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 increasing 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 that 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 pregnancy 

 become more marked. As a rule these are " insensible " contrac- 

 tions, 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 parturition enter 

 upon this phase of activity until a certain time has been run. In 

 the human subject the period of gestation generally lasts from 

 275 to 280 days, i.e. about 40 weeks, the general custom being to 



