MALE PERINEUM 351 



the superficial fascia of the urogenital diaphragm and 

 passing either superficial or deep to the superficial trans- 

 verse muscle, then they run forwards in the urogenital triangle 

 to the skin of the scrotum. As they pass forwards they 

 anastomose with the long perineal branch of the posterior 

 cutaneous nerve of the thigh. 



The deep branch of the perineal nerve passes deep to the 

 superficial transverse perineal muscle and ends in branches 

 to the deep transverse muscle, the superficial perineal muscles, 

 and the bulb of the penis. 



Dissection. Instead of searching for the long perineal branch of the 

 posterior cutaneous nerve of the thigh at the point where it becomes super- 

 ficial, and then following it towards its distribution, it is much easier to 

 find it after it has entered the perineal pouch of fascia. Here it will be 

 discovered lying in close relation to the two preceding nerves, but to the 

 lateral side of them. Trace it forwards and backwards. It communicates 

 with the inferior hsemorrhoidal nerve, and also with the posterior super- 

 ficial perineal nerve. 



The long perineal branch of the posterior cutaneous nerve of 

 the thigh (O.T. long pudendal nerve) pierces the deep fascia of 

 the thigh a short distance in front of the tuber ischiadicum, 

 and about an inch and a half to the lateral side of the 

 margin of the pubic arch. As it proceeds forwards it inclines 

 medially, and, piercing the attachment of Colles' fascia to 

 the margin of the pubic arch, it accompanies the other 

 vessels and nerves to the scrotum, the lateral and front part of 

 which it supplies. 



Dissection. Divide the superficial perineal vessels and nerves, and 

 throw them aside. 



Root of the Penis. At this stage of the dissection the 

 student should consider the position of the urogenital 

 diaphragm, and the relation which it bears to the root of the 

 penis. The urogenital diaphragm is a strong triangular parti- 

 tion which stretches across the pubic arch and separates the 

 anterior part of the perineum from the pelvis. It consists of 

 the deep transverse muscle of the perineum, and the sphincter 

 urethrae membranacece, enclosed between two layers of fascia, 

 an upper and a lower. The two layers of fascia are blended 

 together anteriorly and posteriorly. They are attached laterally 

 to the margins of the pubic arch, and they enclose between 

 them a space which encloses not only the muscular part of 

 the diaphragm but also the membranous portion of the 



