464 THE UTEEUS. 



longer of the two, while the anterior, although projecting less from its 

 vaginal attachment, is lower in position, and, when the tube is closed, 

 comes into contact with the posterior wall of the vagina. These 

 ])orders or lips are geneiieilly smooth, but, after parturition, they 

 frequently become irregular, and are sometimes fissured or cleft. 



The walls of the uterus are of great thickness, and the cavity is thus 

 proportionately much reduced in size. The part Avithin the body is 

 triangular, and flattened from before backwards, so that its anterior 

 and posterior walls touch each other. The base of the triangle is 

 directed upwards, and is curvilinear, the convexity being turned to- 

 wards the interior of the uterus. The cavity, narrowing gradually, is 

 prolonged through the wall of the organ towards its two superior 

 angles, at each of which a minute foramen leads into the narrow canal 

 cf "the Fallopian tube. At the junction of the body with the neck, the 

 cavity is slightly constricted, and thus forms what is sometimes named 

 the hiternal orifice {os uteri internum, isthmus vel ostium uteri) ; this 

 opening is often smaller than the os externum, and is of a circular form. 

 That portion of the cavity which is within the neclo is tubular and slightly 

 flattened before and behind ; it is somewhat dilated in the middle, and 

 opens inferiorly into the vagina by the os tincce. Its inner surface is 

 marked by two longitudinal ridges or columns, which run, one on the 

 anterior, the other on the posterior wall, and from both of which rugas 

 are directed obliquely upwards on each side, so as to present an appear- 

 ance which has been named arior vitm uterinus, also 2)almce jjlicatce : 

 this structure is most strongly marked anteriorly, 



Structuke. — The walls of the uterus consist of an external serous 

 covering, an internal mucous membrane, and a thick intermediate 

 substance which is chiefly muscular. The serous covering or peritoneal 

 layer has been already referred to. 



Muscular Wail. — The thick middle part of the wall of the uterus 

 is of a very dense consistence : it is mainly composed of bundles of 

 muscular fibres of the plain variety, of small size in the unimpregnated 

 uterus, but greatly enlarged in the gravid state. These fibres inter- 

 lace closely with each other, but are disposed in bands and layers, and 

 are intermixed with fibro-areolar tissue, a large number of blood-vessels 

 and lymphatics, and some nerves. The areolar tissue is more abundant 

 near the outer surface. The arrangement of the muscular fibres is best 

 studied in the uterus at the full period of gestation, in which the bands 

 and layers formed by them become augmented in size, and much more 

 distinctly developed. They may be referred to three sets or orders, 

 viz., external, internal, and intermediate. Those of the external set are 

 arranged partly in a thin superficial sheet, immediately beneath the 

 peritoneum, and partly in bands and incomplete strata, situated more 

 deeply. A large share of these fibres, beginning as longitudinal bands 

 at the cervix, arch transversely and obliquely over the fundus and 

 adjoining part of the body of the organ, and converge at either side 

 towards the commencement of the round ligaments, along Avhich they 

 are in part prolonged to the groin. Others pass oft' in like manner to 

 the Fallopian tubes, and strong transverse bands from the anterior and 

 posterior surfaces are extended into the ovarian ligaments. A con- 

 siderable number of thinly scattered fibres also pass at each side into 

 the duplicature of the broad ligament, and others are described as run- 

 ning back from the cervix of the uterus into the recto-uterine folds of 



