INTERNAL PTDIC 573 



pyrifonuis, ()l)tur:it()r intrvnus, and gcniclli iimscles, anastomosing with the piulic, 

 the internal (•ircunill<'.\, and the oljturator arteries. 



(4) The anastomotic branch crosses the external rotator muscles either over 

 or under the great sciatic nerve, and contributes to the formation of the so-called 

 crucial anastomosis by anastomosing -with the first perforating below, the termi- 

 nation of the internal circumiiex internally, and the transverse branch of the 

 external circumflex externally (fig. 369). 



(5) The articular branches pass beneath the external rotator muscles with the 

 nerve to the quadratus femoris, and send several filaments into the posterior part 

 of the capsule of the hip-joint. 



(6) The cutaneous branches turn round the lower border of the gluteus maxi- 

 mus, along with l)ranchcs of the small sciatic nerve, and supj^ly the integument of 

 that region. 



(7) The comes nervi ischiatici is a long slender vessel which passes down 

 the back of the thigh with the great sciatic nerve, to Avhich it sends numerous 

 branches. It anastomoses Avith the internal circumflex, and with the first, second, 

 and third perforating arteries, and with the termination of the profunda, or fourth 

 perforating. After ligature of the femoral in Scarpa's triangle, this artery becomes 

 greatly enlarged, and contributes through its anastomosis with the above-mentioned 

 arteries to the supply of the parts below the ligature. 



8. THE INTERNAL PUDIC ARTERY 



The internal pudic artery — the smaller of the two terminal branches of the 

 anterior division of the internal iliac artery — comes off wdth the sciatic, the other 

 terminal branch, either separately or as a common trunk, opposite the pyriformis 

 muscle. It descends with the sciatic over the pyriformis and sacral plexus of 

 nerves, lying anterior and internal to the latter artery as far as the lower liorder of 

 the great sciatic foramen, where it passes out of the pelvis l^etween the pyriformis 

 and coccygeus muscles. It then winds over the outer surface of the spine of the 

 ischium under cover of the gluteus maximus, and re-enters the pelvis through the 

 lesser sciatic notch. Running forwards over the obturator internus muscle, it 

 passes through the base of the triangular ligament, and, continuing its course 

 along the ramus of the pubes, gives off between the two layers of the triangular 

 ligament the artery of the crus and the artery of the bulb, and is continued through 

 the anterior layer of the ligament as the dorsal artery of the penis. 



The relations of the artery may be considered: — (1) As it lies within the 

 pelvis; (2) as it crosses the spine of the ischium; (3) as it lies on the obturator 

 internus muscle, in the outer Avall of the ischio-rectal fossa; and (4) as it lies 

 between the two layers of the triangular ligament. 



(1) ^A(^ithin the pelvis the artery crosses the pyriformis muscle and sacral 

 plexus of nerves, lying somewhat anterior and internal to the sciatic artery, which 

 is usually given off from the internal iliac along with it. At the lower border of 

 the sciatic foramen it leaves the pelvis by passing between the pyriformis and 

 coccygeus muscles along with the sciatic artery, the pudic nerve, the greater and 

 lesser sciatic nerves, and the nerve to the obturator internus. 



(•2) As it crosses the spine of the ischium it has a companion vein on either 

 side, the pudic nerve on its inner side, and the nerve to the obturator interims (»n 

 its outer side. It is covered by the gluteus maximus muscle, and more or less by 

 the overlapping edge of the great sacro-sciatic ligament. In a thin sul)ject it can 

 be felt pulsating as it crosses the ischial spine. A s])ot taken at the junction of 

 the inner with the outer two-thirds of a line drawn from the top of the great 

 trochanter with the femur rotated inwards to the base of the coccyx, indicates 

 externally the situation of the artery as it crosses the ischial spin(\ In this situa- 

 tion it may, in a thin subject, be compressed. The branches of the artery in tliis 

 part of its course are: (a) Small twigs to the gluteus maxinuis; (^) a small branch 

 to the ol)turator internus which accompanies the nerve to that muscle; (r) a sacral 

 branch which i)ierces the great sciatic ligament and anastomoses with the sciatic 

 artery. 



