MALE PERINEUM 343 



Make a deep incision into it with the knife, and a bursa 

 will be displayed intervening between the fascia and bone. 

 This bursal sac is frequently intersected by strong fibrous 

 bands or cords. In this locality the superficial fascia acts 

 as a cushion on which the tuber ischiadicum rests when the 

 body is in the sitting posture. 



But, again, if the superficial fascia be now followed anteriorly, 

 over the urogenital triangle, another change in its character 

 becomes manifest. The farther forwards it is traced the 

 scarcer becomes the fat which it contains in its meshes. In 

 the scrotum the fat entirely disappears and gives place to a 

 thin layer of involuntary muscular fibres. These fibres con- 

 stitute the dartos muscle, and are recognised by their ruddy 

 colour. The rugosity of the scrotal integument is caused 

 by their contraction. 



Over the urogenital triangle the superficial fascia can be 

 shown to consist of two very definite layers. The superficial 

 layer is fatty and is not confined to this region. In fact, it is 

 simply a portion of the general fatty covering of the body. 

 Posteriorly, it is continuous with the plugs of fat which fill up 

 the ischio-rectal fossae ; on either side, it leaves the perineum 

 and becomes continuous with the fatty tissue on the medial 

 aspects of the thighs. The deep layer is of an altogether 

 different nature. It is a dense membranaceous stratum, devoid 

 of fat, which is spread over the urogenital triangle. It is 

 called the fascia of Colles. This sheet of fascia forms very 

 definite attachments around the limits of the urogenital triangle. 

 Thus, on either side, it is fixed to the anterior Tips of the rami 

 of the pubis and ischium, whilst, posteriorly, it is tucked round 

 the two superficial transverse perineal muscles and blends 

 with the base of the fascia of the urogenital diaphragm (O.T. 

 triangular ligament). A pouch is thus formed, bounded 

 superficially by the fascia of Colles, deeply by the urogenital 

 diaphragm, laterally by the attachment of these to the sides of 

 the pubic arch, whilst, posteriorly, it is closed by the union of 

 the fascia of Colles with the base of the fascia of the urino- 

 genital diaphragm (Fig. 129, p. 344). Within this pouch 

 certain important parts are placed viz., the superficial peri- 

 neal muscles, the perineal vessels and the scrotal nerves, the 

 long perineal branch of the posterior cutaneous nerve of 

 the thigh, the bulb and crura of the penis, and the termina- 

 tion of the pudendal artery. The pouch is partially divided 



