1370 



THE UR1NOGENITAL ORGANS 



the pubic arch, from which it is separated by the dorsal vessels and nerve of the 

 penis, and some muscle fibres. Its posterior convex surface is separated from 

 the rectum by a triangular mass of tissue which constitutes the perineal body. 

 As it pierces the superficial layer of the triangular ligament the fibres around the 

 opening are prolonged over the tube and fix the two structures firmly to each other. 

 The membranous urethra is surrounded by cavernous tissue and by the Compressor 

 urethrae muscle (m. sphincter urethrae membranaceae) (Fig. 340). On the floor 

 of the membranous urethra is the anterior extremity of the verumontanum. 

 Behind this part of the urethra, on each side of the middle 

 line, are Cowper's glands (Figs. 336 and 1111). When the 

 urethra is empty the mucous membrane of this part is 

 MM thrown into longitudinal folds, which are obliterated by dis- 

 tention. 



The penile or spongy portion (pars cavernosa) (Figs. 

 1119 and 1121) is the longest part of the urethra, and is 

 contained in the corpus spongiosum. It is about six inches 

 (15 cm.) in length, and extends from the termination of the 

 1 MM - membranous portion to the meatus urinarius. Its proximal 

 end is fixed in position and unchangeable in direction. Its 

 distal end is movable and changeable in direction. Com- 

 mencing just below the triangular ligament it is first directed 

 forward through the bulb ; it then passes downward and for- 

 ward, the turn beginning at the point of attachment of the 

 suspensory ligament of the penis (Fig. 1111). The direction 

 of the spongy portion of the urethra is changed by altera- 

 tions in the position of the penis. When the canal is closed 

 MM the anterior and posterior walls are in contact (roof and 

 floor), except in the glans penis, where the lateral walls 



FIG. 1120. Cross-sec 

 tion of the male urethra 

 at various distances from 

 its free end, showing 

 marked alterations of 

 form. (Testut.) 



PROBE IN 



ACUNA MAQNA 

 QLANS 



RIGHT LIP OF MEATUS 



LATERAL LACUN/E .. 

 UPPER WALL OF URETHRA" 



SPONGY BODY cut surface- 



-SKIN 



--SIDE OF URETHRA 



-LARGE LACUNA 



SPONGY BODY cut surface 



MEDIAN LACUNXE 



CORPUS 



SPONGIOSUM 



FIG. 1121. -The distal port:on of the male urethra, laid open on Ms 

 posterior (underl surface, showing the lacuna. (Testut.) 



come together. The calibre of the spongy urethra varies in different por- 

 tions of the tube. It is narrow and of uniform size in the body of the penis, 

 measuring about one-third of an inch (9 mm.) in diameter; it is dilated behind, 

 within the bulb (13 to 14 mm.), and again anteriorly within the glans penis (12 

 4 mm.), where it forms the fossa navicularis (fossa navicularis urethrae}. In 

 the roof of the fossa navicularis there is a transverse fold of mucous membrane, 



