URETHRA. 799 



cul-de-sac about a quarter of an inch in length, which runs upwards and back- 

 wards in the substance of the prostate, beneath the middle lobe: its prominent 

 upper wall partly forms the verumontanum. Its walls are composed of fibrous 

 tissue, muscular fibres, and mucous membrane; and numerous small glands 

 open on its inner surface. It has been called by Weber, who discovered it, the 

 uterus masculinus, from its supposed homology with the female organ. 



The membranous portion of the urethra extends between the apex of the pros- 

 tate and the bulb of the corpus spongiosum. It is the narrowest part of the 

 canal (excepting the orifice), and measures three-quarters of an inch along its 

 upper and half an inch along its lower surface, in consequence of the bulb 

 projecting backwards beneath it below. Its upper concave surface is placed 

 about an inch beneath the pubic arch, from which it is separated by the dorsal 

 vessels and nerves of the penis, and some muscular fibres. Its lower convex 

 surface is separated from the rectum by a triangular space, which constitutes 

 the perineum. The membranous portion of the urethra perforates the deep 

 perineal fascia ; and two layers from this membrane are prolonged round it, the 

 one forwards, the other backwards; it is also surrounded by the Compressor 

 Urethrae muscle. Its coverings are mucous membrane, elastic fibrous tissue, a 

 thin layer of erectile tissue, muscular fibres, and a prolongation from the deep 

 perineal fascia. 



The spongy portion is the longest part of the urethra, and is contained in 

 the corpus spongiosum. It is about six inches in length, and extends from 

 the termination of the membranous portion to the ineatus urinarius. Com- 

 mencing below the symphysis pubis, it ascends for a short distance, and then 

 curves downwards. It is narrow, and of uniform size in the body of the penis, 

 measuring about a quarter of an inch in diameter; being dilated behind, 

 within the bulb; and again anteriorly within the glans penis, forming the fossa 

 navicularis. A cross section of this canal in the body of the penis has its long 

 diameter transverse; but in the glans, that diameter is directed vertically. 



The bulbous portion is a name given, in some descriptions of the urethra, to 

 the posterior dilated part of the spongy portion contained within the bulb. 



The meatus urinarius is the most contracted part of the urethra; it is a verti- 

 cal slit, about three lines in length, bounded on each side by two small labia. 

 The inner surface of the lining membrane of the urethra, especially on the floor 

 of the spongy portion, presents the orifices of numerous mucous glands and 

 follicles, situated in the submucous tissue, and named the glands of Littre. They 

 vary in size, and their orifices are directed forwards, so that they may easily 

 intercept the point of a catheter in its passage along the canal. One of these 

 Jacunse, larger than the rest, is situated on the upper surface of the fossa navi- 

 cularis, about an inch and a half from the orifice; it is called the lacuna magnet. 

 Into the bulbous portion are found opening the ducts of Cowper's glands. 



Structure. The urethra is composed of three coats: a mucous, muscular, and 

 erectile. 



The mucous coat forms part of the genito-urinary mucous membrane. It is 

 continuous with the mucous membrane of the bladder, ureters, and kidneys; 

 externally, with the integument covering the glans penis; and is prolonged into 

 the ducts of the glands which open into the urethra, viz., Cowper's glands, the 

 prostate gland, and the vasa deferentia and vesiculas seminales, through the 

 ejaculatory ducts. In the spongy and membranous portions the mucous mem- 

 brane is arranged in longitudinal folds when the organ is contracted. Small 

 papillae are found upon it, near the orifice; and its epithelial lining is of the 

 columnar variety, excepting near the meatus, where it is laminated. 



The muscular coat consists of two layers of plain muscular fibres, an external 

 longitudinal layer, and an internal circular. The muscular tissue is most 

 abundant in the prostatic portion of the canal. 



A thin layer of erectile tissue is continued from the corpus spongiosum round 

 the membranous and prostatic portions of the urethra to the neck of the bladder. 



