HAP. i.] FEMALE ORGANS. 353 



changed in character, the cilia of their epithelium being often 

 absent, while the surface is thrown up into a number of ridges, 

 which radiate in an arborescent manner from two main longitu- 

 dinal folds, one on the anterior, the other on the posterior surface. 



The uterine glands secrete a considerable -.quantity of viscid 

 mucus, alkaline or neutral in reaction. Since the cavity of the 

 uterus is so narrow and slit-like as to be almost potential rather 

 than actual, this mucus is found chiefly at the cervix and in the 

 vagina. 



926. At the os uteri there is a somewhat sudden transition 

 from the columnar or finally cubical epithelium, arranged in a single 

 layer, to the epithelium lining the vagina, which like that of the 

 mouth and pharynx is a stratified epithelium consisting of several 

 layers of nucleated cells, the uppermost of which are flattened. The 

 lining membrane of the vagina, in fact, though it is spoken of as a 

 mucous membrane, is in many points allied to the skin ; and its 

 dermis, like that of the skin, is rich in elastic elements, and bears 

 numerous simple or compound papillae, containing vascular loops 

 and nervous endings. A special feature is the presence of numerous 

 permanent ridges, rugce, which contain venous plexus, supported 

 by interlacing bundles of muscular fibres. Though the matter is 

 disputed the evidence goes to shew that the vaginal walls do not 

 possess glands and do not themselves secrete mucus ; such fluid as 

 is present has an acid reaction. 



Outside this mucous coat is a muscular coat of plain muscular 

 fibres, with an outer longitudinal and inner circular layer, and 

 outside this again a fibrous coat. Between the fibrous and mus- 

 cular coat, as well as between the muscular coat and mucous 

 lining, in the situation of the submucosa, are numerous venous 

 plexuses ; the walls of the vagina, in fact, are very vascular, and 

 largely of the nature of erectile tissue. 



927. The uterus is mainly supplied with blood by the 

 uterine arteries, one on each side, coming from the anterior divi- 

 sion of the internal iliac artery, but it also receives blood from 

 a branch of the ovarian artery, coming direct from the aorta. 

 The blood finds its way back from the uterus by the uterine 

 and ovarian veins, that from the venous plexuses of the vagina 

 falling into the internal iliac. 



The lymphatics of both uterus and vagina are abundant, 

 numerous plexuses, lymph capillaries and lymph spaces being 

 present in both the muscular and mucous coats. 



Concerning the nerves of the uterus, we will speak later on. 



The Ovary. 



928. In the embryo, at a particular spot on each side of the 

 cavity which is called the body cavity, and which becomes in the 



23 



