356 ABDOMEN 



of the pudendal nerve. It supplies twigs to the skin, to the 

 muscles of the perineum, and to the bulb of the penis. The 

 cutaneous scrotal branches have already been followed out. 

 Muscular twigs, occupying a deeper plane, may be traced to 

 each of the three superficial perineal muscles and to .the 

 levator ani, whilst a few minute offsets pierce the inferior 

 fascia of the urogenital diaphragm to supply the deep 

 transversus perinei muscle. The nerve to the bulb is a 

 small branch which breaks up into filaments which enter the 

 hinder part of the corpus cavernosum urethrae. 



Perineal Triangles. If the superficial perineal muscles be 

 now examined, in regard to the relations which they hold to 

 each other, the student will see that they constitute the 

 boundaries of a small triangular space upon each side of 

 the middle line. The base of the triangle is formed by the 

 superficial transversus perinei ; laterally it is limited by the 

 ischio-cavernosus, and medially by the bulbo-cavernosus. Let 

 the student now place the point of his finger within this 

 space and press upwards and backwards. He will perceive 

 that it rests upon a strong resisting membrane. This is the 

 lower fascia of the urogenital diaphragm (O.T. triangular 

 ligament), which therefore forms the roof of the space. 



Dissection, To bring the lower fascia of the urogenital diaphragm 

 fully into view, it is necessary in the first place to remove the super- 

 ficial perineal muscles. When this is done the three divisions of the root 

 of the penis are exposed to view, and their manner of attachment (which 

 has already been described, p. 354) can be studied. Detach, in the next 

 place, the left crus of the penis from the side of the pubic arch, and turn it 

 aside. This must be effected with care, so as not to destroy the attach- 

 ment of the ligament to the side of the pubic arch, or to injure the 

 pudendal artery and dorsal nerve of the penis, which pierce the anterior 

 part of the ligament. 



Lower Fascia of the Urogenital Diaphragm (O.T. Super- 

 ficial Layer of the Triangular Ligament). This is now seen 

 to be a strong aponeurotic membrane which stretches across 

 the pubic arch. It must be regarded as lying in the same 

 morphological plane as the bony and ligamentous wall of 

 the pelvis, and as completing the pelvic wall in front, much 

 in the same manner as the obturator membrane fills up the 

 gap formed by the obturator foramen. 



Upon each side the lower fascia of the urogenital diaphragm 

 is attached to the margins of the rami of the pubis and 

 ischium. Its base is somewhat indefinite, and has already 

 been seen to blend along the posterior border of the super- 



