290 Anatomy Applied to Medicine and Surgery. 



the skin and mucous membrane and corresponds to where 

 the external and internal sphincter" muscles meet. 



The anus is in the middle line of the anal triangle, 

 about one and a half inches in front of the tip of the 

 coccyx. In the median rap he no vessels cross, hence this 

 is the line of safety of the perineum, and, when prac- 

 ticable, incisions are made in this line. The ischio-rectal 

 fossa measures, from before, backwards, two inches. Its 

 width, from the ischial tuberosity to the anus, is one inch 

 while its depth is about two or three inches, the greatest 

 depth being near the ischium. The transversus perinei 

 artery runs from a point at the anterior extremity of the 

 ischial tuberosity to the central point of the perineum. 

 (The internal pudic vessel and nerve lie on the outer side 

 of the fossa in a sheath of the obturator fascia (Alcock's 

 canal), and are situated about one and a half inches above 

 the lower border of the tuberosity of the ischium, while 

 the inferior hemorrhoidal vessels are directed obliquely 

 from the posterior part of the ischial tuberosity to the 

 anus. 



The triangular ligament measures about one and a half 

 inches from its apex at the subpubic arch, to its base at the 

 central tendinous point. It is perforated by the urethra 

 at a distance of about one inch from the pubes, while the 

 dorsal vein of the penis and the subpubic ligament are 

 situated between the opening for the urethra and the un- 

 der margin of the pubic arch. The urethra measures 

 about one and a quarter inches in the prostatic portion, 

 and is also widest in this situation. The membranous 

 portion is the -narrowest, the shortest, and the least dila- 

 table part of the canal, and measures about one-half or 

 three-quarters of an inch in length ; its anterior wall being 

 slightly longer than its posterior wall. The bulbous por- 

 tion is about one and a half inches in length, while the 



