6i8 A MANUAL OF ANATOMY 



the ischio-pubic ramus it contains within its substance the internal 

 pudic vessels and the dorsal nerve of the penis. 



Central Tendinous Point. — Nearly i inch in front of the anus there 

 is a short transverse tendinous septum, about ^ inch long. At its 

 centre it presents a thickening, to which the name of central 

 tendinous point is given. The muscles which meet at this point 

 are as follows : (i) the sphincter ani externus, coming from behind ; 

 (2) the bulbo-cavernosi, coming from before ; (3) the superficial 

 transverse perineal muscles, coming from either side ; and (4) the 

 anterior portions of the levatores ani, which here lie above the 

 posterior portions of the bulbo-cavernosi. The pointed process at 

 the centre of the base of the antero- inferior layer of the triangular 

 ligament of the urethra is also attached to the central tendinous 

 point. 



Bulb of the Urethra. — ^This is the first part of the corpus spon- 

 giosum penis, and is so named from its presenting a bulbous enlarge- 

 ment. It measures about ij inches in length, and about | inch 

 in breadth at its posterior part. Its posterior extremity rests upon 

 the antero-inferior layer of the triangular ligament, and extends 

 as far back as the central tendinous point, where it lies nearly 

 I inch in front of the anus. This part extends fully J inch farther 

 back than the bulbous part of the urethra. It here presents on 

 its under surface, in the middle line, a faint groove indicative 

 of a tendency to a bipartite division at this point. The bulb is 

 invested by a fibrous sheath derived from the circumference of the 

 urethral opening in the antero-inferior layer of the triangular 

 ligament, superficial to which lie the fibres of the chief parts of 

 the bulbo-cavernosi muscles. Each lateral wall of the bulb is 

 pierced by Cowper's duct, which, with its fellow of the opposite 

 side, opens upon the floor of the bulbous part of the urethra 

 fully I inch in front of the antero-inferior layer of the triangular 

 ligament. 



Crus Penis (crus corporis cavernosi penis). — ^This is the posterior 

 attached portion of the corpus cavernosum penis. It is attached 

 to the anterior everted lip of the inner border of the ischio-pubic 

 ramus, superficial to the antero-inferior layer of the triangular 

 ligament. Inferiorly and laterally it is covered by the ischio- 

 cavernosus, and it lies beneath the fascia of Colles. The artery 

 of the corpus cavernosum, having pierced the antero-inferior layer 

 of the triangular ligament, passes between the attached surface of 

 the crus and the ischio-pubic ramus, and enters the deep surface 

 of the crus, to be continued forwards in the centre of the corpus 

 cavernosum. 



Deep Perineal Triangle — Boundaries — External. — ^The crus penis, 

 covered by the ischio-cavernosus muscle. Internal. — ^The bulb of 

 the urethra, covered by the bulbo-cavernosus muscle. Posterior, or 

 Base. — ^The superficial transverse perineal muscle. The floor is 

 formed by the fascia of Colles, with the superficial perineal vessels 

 and the three long scrotal nerves. In the undisturbed position of 



