346 OF THE GENITAL FUNCTION OF WOMAN. 



have proved their lateral position, he described the muscle a> 

 seated in the centre of the fundus uteri. This structure of the 

 inner surface of the fundus of the uterus is still adapted to the 

 explanation of Ruysch, which was, that this produced contraction 

 and corrugation of the surface of the uterus, which the placenta 

 not partaking of, the cohesion of the surface was necessarily 

 broken. 



Further, I have observed a set of fibres of the inner surface 

 of the uterus which are not described. They commence at the 

 centre of the last described muscle, and having a course at first 

 in some degree vorticose, they descend in a broad irregular band 

 towards the orifice of the uterus. These fibres co-operating with 

 the external muscle of the uterus, and with the general mass of 

 fibres in the substance of it, must tend to draw down the fundus 

 and lower segment of the uterus over the child's head. 



I have not succeeded in discovering circular fibres in the os 

 tincae corresponding in place and office with the sphincter of 

 other hollow viscera, and I am therefore inclined to believe, that, 

 in the jelaxing and opening of the orifice of the uterus, the 

 change does not result from a relaxation of muscular fibres sur- 

 rounding the orifice. Indeed, it is not reasonable to conceive 

 that the contents of the uterus are to be retained during the nine 

 months of gestation by the action of a spliincter muscle. The 

 loosening of the orifice, and that softening and relaxation which 

 precede labour, are quite unlike the yielding of a muscular ring." 



