372 



THE MUSCLES AND FAKCIJE 



posterior form a thin layer, which is lost on the anterior surface of the triangular 

 ligament; the middle fibres encircle the bulb and adjacent parts of the corpus 

 spongiosum, and join with the fibres of the opposite side, on the upper part of the 

 corpus spongiosum, in a strong aponeurosis ; the anterior fibres, the longest and 

 most distinct, spread out over the sides of the corpus cavernosum, to be inserted 

 partly into that body, anterior to the Erector penis, occasionally extending to the 

 os pubis ; partly terminating in a tendinous expansion, which covers the dorsal 

 vessels of the penis. The latter fibres are best seen by dividing the muscle 

 longitudinally, and dissecting it outward from the surface of the urethra. 



Action. This muscle serves to empty the canal of the urethra, after the 

 bladder has expelled its contents ; during the greater part of the act of micturition 

 its fibres are relaxed, and it only comes into action at the end of the process. The 

 middle fibres are supposed, by Krause, to assist in the erection of the corpus 



GREAT SACRO- 

 SCIATIC LIGAMENT 



Superficial perineal artery. 

 Superficial perineal nerve. 

 Internal pudic nerve. 

 Internal pudic artery. 



FIG. 225. The superficial muscles and vessels of the perinseum. 



spongiosum, by compressing the erectile tissue of the bulb. The anterior fibres, 

 according to Tyrrel, also contribute to the erection of the penis, as they are inserted 

 into, and continuous with, the fascia of the penis, compressing the dorsal vein 

 during the contraction of the muscle. 



The Erector penis (Ischio-cavernous) covers part of the crus penis. It is an 

 elongated muscle, broader in the middle than at either extremity, and situated on 

 either side of the lateral boundary of the perinaeum. It arises by tendinous and 

 fleshy fibres from the inner surface of the tuberosity of the ischium, behind the 

 cruS penis, from the surface of the crus, and from the adjacent portion of the 

 ramus of the ischium. From these points fleshy fibres succeed, which end in an 

 aponeurosis which is inserted into the sides and under surface of the crus penis. 



Nerve-supply. The perineal branch of the internal pudic. 



Actions. It compresses the crus penis and retards the return of the blood 

 through the veins, and thus serves to maintain the organ erect. 



Between the muscles just examined a triangular space exists, bounded 

 internally by the Accelerator urinas, externally by the Erector penis, and behind 



