ANATOMY IX A XUTSHELL. 495 



The "white line," or arcus tenmbtEus, extends from the inner aspect 

 of the spine of the ischium to the back of the os pubis, external to the symphysis, 

 and is formed by a thickening of the obturator fascia where the fascia of Leva- 

 tor ani muscle meets the obturator fascia. This line, of course, is Dot straigb.1 

 because it comforms to the curve of the pelvic wall. 



Buck's fascia is a continuation of Colles' fascia which extends forward 

 upon the penis, which it invests completely, as far as the gland.-. 



The triangular ligament of the urethra. One set of anatomists describe 

 the anterior layer of the deep perixeai. fasci \ as the triangular ligament, 

 while another set include the posterior layer of the deep perineal fasci \. 

 thus making two layers of the triangular ligament. Still a third set of anat- 

 omists include Colles' fascia in the triangular ligament, thus making three 

 leaflets in the triangular ligament. Where these three triangular leaflets meet 

 posteriorly is called the perineal ledge, and as they pass forward towards 

 the symphysis pubis there are two spaces between these three leaflets. The 

 one between the first two leaflets is called the superficial perineal inter- 

 space, and contains the following structures: 



1. The crura of the corpora cavernosa. 



2. The bulb of the corpus spongiosum. 



3. Scattered fibers of the Superficial transverse periinei muscle. 



4. Arteiies of the corpora cavernosum and dorsal vessels of the penis. 



5. Dorsal nerves of the penis. 



6. Superficial perineal vessels and nerves. 



The space between the second and third leaflets of the triangular ligament 

 is called the deep perineal interspace and contains: 



1. The membranous urethra. 



2. C'owper's glands. 



3. Internal pudic arteries. 



4. Pudic veins. 



5. The pudic lymphatics. 



6. Dorsal nerves of the penis. 



7. The deep Transverse peiinaei and Compressor urethra muscles. 



The central tendon of the perineum is about half an inch in front of the 

 amis, in the middle of the perineal ledge, and is the place where the External 

 sphincter ani and Accelerator mime and Transverse perinaei muscles meet. 



Alcock's canal is about two inches in length and is formed by a delamina- 

 tion of the obturator fascia. It is situated on the outer wall of the ischio- 

 rectal fossa, extending from the lesser sacro-sciatic foramen to the lower border 

 of the triangular ligament. The internal pudic vessels and nerve pass through 

 this canal. (Plate CCLXX.) 



The pelvic fascia lines the cavity of the pelvis and at the white line it divides 

 into (1 ) rk< Tn-\ ESU \\. FASCIA, which is called visceral layer of the pelvic fascia. 

 This layer descends from the white line over the Levator ani muscle, over the 

 prostate gland. rentum, vesiculae seminales and the bladder. It forms the true 

 ligaments of the bladder. (2) The obturator fascia, which is called the 



