LABOR-PAINS. 279 



that if we place a finger on the point of the ovum where it tends 

 strongly to engage in the opening, we find that the head of the 

 foetus, instead of pressing into it, actually retires from below up- 

 wards, being repelled by the fluids which pass beiwixt it and the 

 womb in order to fill up the bag of waters. 



This however does not imply that the child has nothing to do with 

 the production of this phenomenon, but merely that it is not the 

 active cause in it, and can only concur in it by being under the in- 

 fluence of some other power. 



701. The real cause of it is to be found in the contractions of 

 the womb. It is of the essence of fleshy fibres to shorten themselves, 

 and tend to approach a straight line, when they contract; the womb is 

 composed of curved fibres, the most numerous and strongest of which 

 occupy its fundus and body, and are principally placed lengthwise; 

 the cervix is the weakest part of the whole organ; the ovum is an in- 

 compressible body. Now, it is ma'iifest that with such a disposition, 

 the dilatation of the cervix must commence with the contractions of 

 the womb. The vertical and oblique fibres, by their two extremities, 

 which are their movable points, draw the horizontal fibres to which 

 they are attached, or with which they are interlaced, upwards to- 

 wards their middle, where is to be found the real fixed point. The 

 transverse fibres, in contracting upon the ovum, a smooth oval body, 

 necessarily tend to slide towards its apex or towards its base; but as 

 tliey are at least as numerous above as below the middle transverse 

 zone, it follows, that the circular fibres of the inferior portion of the 

 uterus will, in any general contraction, be found to resist, alone, the 

 eflx)rts of all the longitudinal and circular fibres of its superior half. 



On the other hand, as the ovum can only be pushed by the con- 

 cavity of the uterine fibres towards the least resisting point of the 

 organ, it engages in the partly open orifice, and becomes a powerful 

 though secondary cause of the dilatation of the os uteri, and in this 

 case acts like a wedge: it is an inert force which acts in aid of a vital 

 or organic force. Thus it may be admitted that the ovum is de- 

 pressed while the os uteri is raised upwards; in other words, that 

 these two parts, under the influence of the same power, the uterine 

 contraction, slide one upon the other, and that the latter must dilate 

 in the direct ratio of the force which causes the former to descend. 



At the commencement of labor, when the os uteri just begins to 

 open, it is known to contract instead of dilating during the pain, but 

 in such a way, notwithstanding, that it remains larger after the pain 

 than it was before it. At a more advanced stage, when the bag of 

 waters begins to form, we observe, on the contrary, that the os uteri 

 dilates considerably during the contraction, and contracts somewhat 



