ACTION OP THE FEMALE. 981 



the occurrence of the uterine nisus may be induced by a variety of causes, 

 several of which probably concur in the normal act of Parturition. For, in the 

 first place, the state of development of the muscular substance of the uterus 

 can scarcely be without a considerable influence on this operation. We see it 

 undergoing a gradual augmentation during the period of pregnancy, without any 

 demand being made upon its functional activity ; it gradually becomes more and 

 more irritable, contractions being far more readily excited in it by electrical or 

 other stimulation, in the later, than in the earlier months of pregnancy; and at 

 last this irritability seems to reach its acme, in virtue of the nutritive changes 

 which have been progressively taking place in it, and to discharge itself in one 

 powerful effort. That the parturient effort, however, is not solely dependent 

 upon the state of development of the Uterus, appears from several considera- 

 tions : and, in the first place, from the very curious fact that, in cases of Extra- 

 uterine pregnancy, contractions resembling those of labor take place in its walls. 

 Moreover, various states of constitution, especially that which is designated as 

 irritability, may induce the occurrence of the parturient efforts at an earlier 

 period; and this constitutes Abortion, or Premature Delivery, according to the 

 viability of the child. There are some women, in whom this regularly happens 

 at a certain month, so that it seems to be an action natural to them ; but it is 

 always to be prevented, if possible, being injurious alike to the mother and the 

 child ; and this prevention is to be attempted by rest and tranquillity of mind 

 and body, and by a careful avoidance of all the exciting causes which may pro- 

 duce uterine contractions by their operation on the Nervous system. Among 

 the causes of Abortion, however, the death of the foetus, or an abnormal state of 

 the placeutal structure, is one of the most common; and thus we have a very 

 distinct proof of the influence which the state of the contents of the uterus has 

 on the induction of parturient effort. In fact, what may be termed the matu- 

 ration of the uterus and its contents a condition analogous to that which pre- 

 cedes the dropping of ripe fruit, and which is acquired by the completion of the 

 developmental process appears to have more influence in determining the 

 normal parturient effort, than any other cause which can be assigned. Certain 

 preparatory changes are known to be taking place in the uterus itself during 

 the last two or three weeks of gestation ; for its upper part contracts itself more 

 closely around its contents, as if it were bracing itself up for the coming 

 encounter; whilst there is a greater disposition to relaxation of its lower part, 

 as also in the soft parts surrounding the orifice of the pelvis, so that the whole 

 mass descends. It is well known that there is far less aptitude for dilatation in 

 the os uteri before this change takes place ; so that premature labors are fre- 

 quently rendered very difficult and tedious by the resistance which the foetus 

 encounters from the soft parts, notwithstanding that its smaller size enables it 

 to pass more readily through the pelvic canal. The placenta of the fully 

 developed foetus, again, is somewhat in the condition of the footstalk of a 

 ripening fruit; that is, having attained its full evolution as an organ of tem- 

 porary function, its connection tends to become dissevered in virtue of the 

 further changes which take place in itself, quite irrespectively of any external 

 agency. 1 This is very strikingly evinced by the fact, that when the uterus 

 contains two foetuses, and one of them is expelled either in consequence of 

 impeded development or of disease in itself, or because it has attained its own 



itself spontaneously whenever the disturbance in its equilibrium attains a certain intensity. 

 If the movement of the machine be uniform, and other conditions remain the same, the 

 discharge will take place at regular intervals. 



1 Such a change may be easily verified in the placenta of many of the lower animals, 

 such as the cat, in which the foetal and maternal portions remain more distinct than they 

 do in the human female ; for these become far more easily separable from each other, as 

 the period of parturition draws near, than they are at any previous time. 



