460 THE FEMALE EEPEODUCTIVE ORGANS. 



The mucous membrane is whitish, except near the orifice ; it is 

 raised into longitudinal plicre, which are not entirely obliterated by 

 distension, especially one which is particularly marked on the lower or 

 posterior surface of the urethra. Near the bladder the membrane is 

 soft and pulpy, with many tubular mucous glands. Lower down these 

 increase in size and lie in groups between the longitudinal folds, and 

 immediately within and around the orifice, the lips of which are ele- 

 vated, are several larger and wider crypts. 



The lining membrane is covered with a scaly epithelium, but near 

 the bladder the particles become spheroidal. The submucous areolar 

 tissue contains elastic fibres. Outside this there is a highly vascular 

 structure, in which are many large veins. Between the anterior and 

 posterior layers of the triangular ligament, the female urethra is em- 

 braced by the fibres of the compressor urethras muscle. 



The vessels and nerves of the female urethra are very numerous, and 

 are derived from the same sources as those of the vagina. 



THE VAGINA. 



The vagina is a membranous and dilatable passage, extending from 

 the vulva to the uterus, the neck of which is embraced by it. It rests 

 below and behind on the rectum, supports the bladder and urethra in 

 front, and is enclosed between the levatores ani muscles at the sides. 

 It is slightly curved and is directed upwards and backwards : its axis 

 corresponding below with that of the outlet of the pelvis, and higher 

 up with that of the pelvic cavity. In consequence of its curvature and 

 its reaching higher on the back than on the front of the os uteri, its 

 length is greater along the posterior than along the anterior waU, by 

 about an inch and a half. Each end of the vagina is somewhat nar- 

 rower than the middle part : the lower, which is continuous with the 

 vulva, is the narrowest part, and has its long diameter from before 

 backwards ; the middle part is widest from side to side, being flattened 

 from before backwards, so that its anterior and posterior walls are 

 ordinarily in contact with each other : at its upper end it is rounded, 

 and expands to receive the vaginal portion of tlie neck of the uterus, 

 which is embraced by it at some distance above the os uteri. The 

 vagina reaches higher up on the cervix uteri behind than in front, so 

 that the uterus appears, as it were, to be inserted into its anterior wall. 



On the inner surface of the vagina, anteriorly and posteriorly, a 

 slightly elevated ridge extends from the lower end upwards in the 

 middle line, foi-ming the columns of the vagina, or columnar rugarum. 

 Numerous dentated transverse ridges, called rugcc, are also observed, 

 particularly in persons who have not borne children, running at right 

 angles from the columns. These columns and rugfe are most evident 

 near the entrance of the vagina and on the anterior surface, and 

 gradually become less marked, and disappear towards its upper end. 



Structure and connections. — The walls of the vagina are thickest 

 in front, in the vicinity of the urethra, which indeed may be said to be 

 imbedded in the anterior wall of the vaginal passage ; in other situa- 

 tions they are thinner. The vagina is firmly connected by areolar 

 tissue to the neck of the bladder, and only loosely to the rectum and 

 levatores ani muscles ; at the upper end, for about a fourth part of its 

 length, its posterior surface receives a covering from the peritoneum, 



