THE ABDOMEN 619 



the parts the area of the triangle is concealed by the approximation 

 of the bulbo-cavernosus and ischio-cavernosus muscles. When, 

 however, these muscles are held apart there is seen lying deeply 

 in the area one half of the antero-inferior layer of the triangular 

 ligament of the urethra. 



Subpubic Ligament (ligamentum arcuatum). — ^This is a thick 

 band which lies at the antero-superior part of the subpubic arch, 

 where it fills up the subpubic angle. It is attached superiorly to 

 the lower part of the interpubic disc, and laterally to the adjacent 

 parts of the inner lips of the descending pubic rami. It is about 

 \ inch in depth, and is slightly arched. 



Transverse Pelvic or Perineal Ligament. — This band extends 

 transversely between the descending pubic rami two or three lines 

 below the subpubic ligament. Inferiorly it is closely connected 

 with the truncated apex of the antero-inferior layer of the triangular 

 ligament. Between its upper border and the subpubic ligament 

 there is the opening for the backward passage of the dorsalis penis 

 vein. 



Triangular Ligament of the Urethra. — ^This ligament occupies the 

 subpubic arch, which it fills, except at its antero-superior part 

 where it is replaced by the subpubic and transverse pelvic or 

 perineal ligaments. It is composed of two distinct layers, called 

 antero-inferior (perineal) and postero-superior (pelvic). These two 

 layers are united by their bases, but elsewhere they are separated 

 by an interval of about | inch, in which the membranous part of 

 the urethra in the male, and the vagina and urethra in the female, 

 along with other structures to be presently enumerated, lie. 



The antero-inferior layer is also called the subpubic, or deep perineal, 

 fascia. It is triangular, the apex being truncated. The apex is 

 closely connected with the transverse pelvic or perineal ligament, 

 which may be regarded as a part of its fibres. Each lateral margin 

 is attached to the inner border of the ischio-pubic ramus, behind its 

 everted hp, on which it extends as far back as the tuber ischii, lying 

 between the attachments of the crus penis and ischio-cavernosus 

 anteriorly and the compressor urethrae posteriorly. In this direction 

 it measures fully 2 inches. The base is directed downwards and 

 backwards, and is joined by the base of the postero - superior 

 layer and the fascia of Colles. In the middle line the base is pro- 

 jected into a slight process, which is connected with the central 

 tendinous point of the perineum. On either side of this median 

 process the base presents a concave margin where it sweeps down- 

 wards and outwards to the tuber ischii. The length of the antero- 

 inferior layer in the middle line is about ij inches. Its fibres are 

 chiefly disposed transversely. The structures which pierce this 

 layer are as foUows : the urethra, the arteries of the bulb, the 

 arteries of the corpora cavernosa penis, the dorsal arteries and the 

 dorsal nerves of the penis, the superficial perineal vessels and nerves, 

 and the ducts of Cowper's glands. 



Urethral Opening. — ^This apertiire is situated in the middle line 



