30 



penis, (or the mammary glands) is drained mainly by the large V. pudenda 

 externa (PI. V, 42), which lies in the subpubic groove of the pelvis. 



A. pudenda interna (PI. V, 37). 



Care must be exercised in tracing this artery especially its distal half, not 

 to injtire its numerous small branches or the neighboring nerves; the adjoin- 

 ing veins however, may be cut if desired. The urocyst and all of the other 

 pelvic organs should be turned dorsally. The A. pudenda interna arises 

 from the A. iliaca interna near the origin of the latter vessel. It extends 

 posteriorly across the lateral wall of the pelvic cavity, lying close to the 

 dorsal border of the iliac portion of the M. obturator internus. Opposite 

 the superior ischiatic spine the artery is covered by the M. retractor ani 

 which should be transected and turned aside (PI. V, 21 and 21'). Near the 

 lesser sacro-sciatic foramen the artery either passes through the sacro- 

 sciatic ligament i.e. from its inner to its outer surface, or is imbedded in the 

 substance of the ligament. Trace the artery peripherally as far as can 

 be done readily (to the posterior border of M. retractor ani) and then 

 proceed as follows : make a circular cut in the skin of the anal region at a 

 little distance, 4 to 6 cm., from the anal orific; also cut the large bundle of 

 muscle fibres (recto coccygeal, PI. V 23) that attaches the terminal part of 

 the rectum to the coccygeal vertebrae. Cut also, the M. retractor penis 

 (PI. V, 22). Now carefully remove the connective tissue from the side of 

 the anus until the artery and nerves are exposed. The main trunk of the 

 artery terminates in the erctile tissue at the root of the penis. 



Branches of the A. pudenda interna. 



(i) A. umbilicalis (PI. V, 39) arises from the pudenda interna 2 to 3 cm. 



from the origin of that vessel and passes directly to the urocyst. Before 

 birth the A. umbilicalis is a very large vessel and carries the foetal blood 

 to the placenta. After birth the vessel extends only to the urocyst and is 

 very much smaller than in foetal life. 



(2) A. haemorrhoidalis media (or vesico-prostatic) . This small artery 

 in the male, arises from the pudenda interna about 8 cm. from the origin 

 of the latter (or about half way between the origin of the A. pudenda 

 interna and the anterior edge of the M. retractor ani) and runs posteriorly. 

 It supplies small twigs to the rectum, urocyst, prostate gland, and seminal 

 vesicle. Near the ischial arch the A. pudenda interna gives off a small 

 branch — A. perinei — which passes somewhat dorsally at the side of the 

 anus which it supplies; the A. pudenda interna also gives off twigs to the M. 

 bulbo-cavemosus and the skin of the perineum. In the female the corres- 

 ponding artery is much larger and gives off the A. uterina caudalis. This 



