MALE PERINEUM 161 



Arterise Hsemorrhoidales Inferiores. The inferior haemor- 

 rhoidal arteries, usually two or three in number, are branches 

 of the internal pudendal. They pierce the medial wall of the 

 canal in the obturator fascia, and pass medially, through the 

 fat of the ischio-rectal fossa, to supply the anal canal and 

 the muscles in connection with it, as well as the skin around 

 the anus. Around the anal canal they anastomose with the 

 corresponding arteries of the opposite side, and with branches 

 from the middle and superior haemorrhoidal arteries. They 

 also send a few twigs round the lower border of the glutseus 

 maximus, in company with the perforating cutaneous nerve, 

 to supply the skin of the lower part of the buttock. 



N. Haemorrhoidalis Inferior. The inferior haemorrhoidal 

 nerve accompanies the vessels of the same name. It may 

 proceed directly from the sacral plexus, but more frequently 

 it is a branch of the pudendal nerve. It perforates the 

 medial wall of the canal in the obturator fascia, enters the 

 ischio-rectal fossa, and then it breaks up into muscular, 

 cutaneous, and communicating branches. The muscular 

 twigs supply the external sphincter ani ; the cutaneous offsets 

 are given to the skin which surrounds the anus ; while the 

 communicating filaments pass forwards to join the scrotal 

 nerves and the long perineal branch of the posterior cutaneous 

 nerve of the thigh. 



Perineal Branch of Fourth Sacral Nerve. The perineal 

 branch of the fourth sacral nerve is small. It enters the 

 ischio-rectal fossa by piercing the coccygeus muscle at the 

 side of the coccyx. It is distributed to the skin between 

 the anus and coccyx, and to the external sphincter ani 

 muscle. 



The perineal artery and the superficial and deep branch 

 of the perineal nerve, which were found in the anterior angle 

 of the fossa close to the lateral wall, will be traced forwards, 

 in the next stage of the dissection, in the urogenital triangle. 



Ano-coccygeal Body. An indefinite mass of muscular and 

 fibrous tissue which lies between the tip of the coccyx and 

 the anus receives the name of ano-coccygeal body. It is seen 

 best in sections through the pelvis, and it requires notice on 

 account of the support which it gives to the lower part of 

 the rectum and the anal canal. The muscular tissue which 

 enters into its constitution belongs to the levator ani and 

 the external and internal sphincter muscles (Symington). 



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