1536 PARTURITION. [BOOK iv. 



foreign to itself, the placenta and membranes, the latter consist- 

 ing of amnion, chorion, the whole of the remains of the decidua 

 reflexa and a variable part of the decidua vera ; and, under normal 

 conditions, these are by the last expulsive efforts ejected with or 

 immediately after or soon after the child. As a rule the membranes 

 are ruptured and the amniotic fluid escapes before the head ex- 

 trudes, but at times the child is born still surrounded by the intact 

 membranes with their contained fluid ; it comes into the world in 

 its " caul." 



When the placenta and membranes have left the uterus (they 

 not unfrequently are lodged for a while in the vagina), the tonic 

 contraction or "retraction" spoken of above, which during the 

 whole of labour has been following up the advance of the foetus, 

 and progressively lessening the uterine cavity, continues its work 

 and serves an important purpose. When the last pain of labour, 

 by which the emptied uterus is gathered up into a small hard 

 ball, passes away, the walls under normal conditions do not wholly 

 relax, a permanent tonic contraction keeps the walls thick and in 

 contact, thus closing the uterine cavity; and over this compact and 

 closed uterus waves of rhythmical contraction, the " after-pains," 

 still for a while pass without altering its permanent condition. 

 By this continued contraction or retraction, not only the open, 

 torn ends of the vessels of the decidua but all the vessels through- 

 out the thickness of the uterine walls are so compressed that 

 all extensive bleeding is prevented. Should this continued con- 

 traction give away to relaxation, haemorrhage or " flooding" follows. 

 This retraction or tonic contraction, whatever be its exact nature, 

 which is so conspicuous in the uterus but which perhaps may be 

 recognized in a lesser degree as mere ordinary tonic contraction in 

 other rhythmically contracting organs, in the bladder, in the 

 intestine, and even in the heart, appears to serve more than one 

 purpose in the work of the uterus ; by continually lessening the 

 uterine cavity it renders more efficient during labour the rhythmic 

 uterine "pains," by compressing the blood vessels during labour 

 it gradually shuts off the extravagant blood supply now no longer 

 needed, and by continuing that compression after labour and by 

 closing the uterine cavity it prevents haemorrhage and wards off 

 the evil effects which the free entrance into the uterine cavity 

 of foreign organisms might bring about. And probably it is on 

 account of its great usefulness that this peculiar form of muscular 

 activity is so prominent in the uterus. 



Even before labour proliferation of the epithelioid cells may 

 be observed in the lining membrane of the uterine vessels ; these 

 are rapidly increased after labour is completed, and form part of 

 the healing processes which follow. The tonic contraction of 

 which we have been speaking is maintained until the blood vessels 

 are permanently closed by these nutritive healing processes. After 

 birth the muscular elements of the uterus dwindle, many of the 



