THE ABDOMEN 627 



ing the back of the scrotum they divide into long slender branches 

 which supply the scrotal integument. 



In the anterior division of the perineum the two superficial 

 perineal nerves communicate freely, and are accompanied by the 

 long pudendal nerve of Soemmering, which is a branch of the small 

 sciatic. This nerve, having pierced the fascia lata about i inch in 

 front of the tuber ischii, passes inwards over the ischio-pubic ramus 

 and through the fascia of Colles. It then runs forwards and inwards 

 beneath that fascia to the scrotum, to take part in the supply of 

 its integument, and it communicates with the external or posterior 

 superficial perineal nerve. 



The two superficial perineal nerves and the long pudendal nerve 

 are known as the long scrotal nerves. 



The deep branch of the perineal nerve furnishes offsets which, 

 with one exception, are muscular in their distribution, and supply 

 the anterior part of the external sphincter, the anterior part of the 

 levator ani, the superficial transverse perineal, the ischio-caver- 

 nosus, and the bulbo-cavernosus. The non-muscular branch, called 

 the nerve of the bulb, pierces the bulbo-cavernosus muscle and the 

 wall of the biilb, to be distributed to the erectile tissue of the 

 corpus spongiosum and the mucous membrane of the spongy part 

 of the urethra. 



The dorsal nerve of the penis is at first contained in Alcock's 

 canal, where it lies above the internal pudic vessels. Having 

 emerged from that canal, it pierces the postero-superior layer 

 of the triangular ligament near its base. It then passes for- 

 wards and upwards, with the fourth part of the internal pudic 

 artery, between the two layers of the triangular ligament, in which 

 situation it lies on the outer side of the internal pudic vessels, and 

 close to the ischio-pubic ramus, being embedded in the compressor 

 urethrse muscle. Its subsequent course is similar to that of the 

 dorsal artery of the penis, which it accompanies. On the dorsum 

 of the penis, where it. lies external to the dorsal artery, it is con- 

 tinued as far as the glans, where it ends in branches for the glans 

 and prepuce. As the nerve lies between the two- layers of the 

 triangular ligament, it gives branches to the compressor urethrae 

 muscle, and it also furnishes the ner\'e of the corpus cavemosum. 

 This latter nerve, having pierced the compressor urethrae and 

 antero-inferior layer of the triangular ligament, enters the crus, 

 and is continued forwards in the corpus cavernosum to supply 

 the erectile tissue of these parts. As the nerve passes along the 

 dorsum of the penis, it supplies numerous branches to the integu- 

 ment of that organ. 



Structures divided in Left Lateral Litliotomy. — The structures divided in 

 this operation are as follows : (i) the skin ; (2) the subcutaneous layer of the 

 superficial fascia ; (3) the deep layer of the superficial fascia or the fascia of 

 Colles; (4) the transverse perineal vessels; (5) the superficial transverse 

 perineal muscle ; (6) the inferior hemorrhoidal vessels and nerve ; (7) the 

 basal part of the antero-inferior layer of the triangular ligament ; (8) the 

 compressor urethrae muscle and the plexus of veins embedded in it ; (-9) the 



