206 SURGICAL ANATOMY OF 



membranous portion of the urethra, which lies between 

 these layers of fascia, and receives a prolongation from 

 each ; the deep transversus perinei ; the internal pudic 

 artery and nerve, the former giving off the artery to the 

 bulb and to Cowper's gland; the artery to the corpus 

 cavernosum, and the dorsal artery of the penis; and just 

 below the urethra, Cowper's glands, their ducts, and the 

 subpubic ligament. Beneath this layer of muscular 

 fibres and vessels is the posterior layer of the triangular 

 ligament, derived from the pelvic fascia. 



Note. Before proceeding with the deep dissection of 

 the perineum it will be found expedient to study the 

 anal region. 



Dissection of the Anal or Ischio-rectal Region. An 

 incision is to be made commencing just in front of the 

 anus, round which it is to be carried to the tip of the 

 coccyx, another at right angles to it, immediately behind 

 the termination of the rectum, and the flaps reflected 

 outwards. As the external sphincter is incorporated 

 with the integument, great care must be taken not to 

 remove it, on dissecting off the flap ; this is next to im- 

 possible, however, if the dissection be conducted in the 

 usual manner, as the skin of the whole of the perineum 

 posteriorly is interwoven with muscular fibres. 



In the middle line of this space lies the anus, the mu- 

 cous membrane of which is not seen, in the normal state, 

 during life. If, however, the anus be gently opened at 

 the junction of the mucous membrane with the skin, a 

 pale line is to be seen, marking the position of the in- 

 ternal sphincter, a thickening of the muscular fibres of 

 the lower portion of the rectum. This band of muscu- 

 lar fibres plays an important part in preventing the heal- 

 ing of ulcers and fissures of the rectum, by keeping the 



