642 



REPRODUCTIVE ORGANS. 



motion of the cilia of the uterine mucous membrane is toward 

 the vagina. In the mucous membrane of the cervix are closed 

 sacs lined by cylindrical or ciliated epithelium ; these are the 

 ovula Nabothi, and are regarded as cystic formations. 



The muscular coat (Fig. 431) consists of three layers : An 

 inner and an outer, both longitudinal ; and a middle circular, which 

 is more highly developed than the other two. The muscular 

 tissue is of the unstriped variety (Fig. 432). 



Ovtllation. The formation of ova in the human female is 



FIG. 431. Arrangement of uterine muscle, as seen from in front after removal of 



serous coat (Helie). 



probably complete two years after birth. Although during this 

 period, and, indeed, even before birth, some ova may undergo 

 development to some extent, still it is not until the period of 

 puberty that there is any approach to regularity in the develop- 

 ment of either the Graafian follicles or the ova. At undetermined 

 periods Graafian follicles rupture and mature ova are discharged, 

 together with the cells of the discus proligerus. This ripening 

 and discharge of ova constitute ovula tion. The cause of the 



