8i4 HUMAN ANATOMY. 



{e) The external branch passes around the external border of the obturator foramen, 

 beneath the external obturator muscle, and terminates by anastomosing with the internal branch 

 and with the internal circumflex from the deep femoral. Near its origin it gives off — 



(flrt) An i}iter)ial branch, which passes downward on the posterior surface of the obturator 

 membrane, under cover of the internal obturator muscle, to the tuberosity of the ischium, and 

 it also gives rise to — 



{bb) An acetabular branch (ramus acetabuli), which passes through the cotyloid notch and 

 supplies the fatty tissue occupying the bottom of the acetabulum. 



(/) The internal branch runs around the inner border of the obturator foramen, beneath 

 the external obturator muscle, and terminates by anastomosing with the external branch. 



Variations. — The obturator artery varies greatly in its origin, and these variations may be 

 divided into two groups, according as the origin is from the internal or the external iliac system 

 of arteries. While the origin of the vessel from the anterior division of the internal iliac is the 

 most frequent, yet, when compared with all the variations taken together, it occurs in some- 

 what less than 50 per cent, of cases. Of other origins from the system of the internal iliac there 

 may be mentioned those from the main stem of the iliac before its division, from its posterior 

 division, and from the gluteal artery. Furthermore, its origin may occur from either the sciatic 

 or the internal pudic artery, although such cases are rare. 



More frequent and of greater importance from the practical stand-point is the origin 

 from the external iliac system, which occurs in about 30 per cent, of cases. In the immense 

 majority of such cases— in almost twenty-nine out of every thirty — the origin is from the deep 

 epigastric artery, being in the remaining cases from the external iliac distal to the deep epigas- 

 tric or from the upper part of the common femoral artery. Undoubtedly the primary relations 

 of the obturator artery are with the internal iliac system of vessels, and the origin from the ex- 

 ternal iliac system is to be regarded as due to the secondary enlargement of an anastomosis nor- 

 mally present and the diminution or inhibition of the original stem of the obturator. Possibilities 

 for such a process are furnished by the normal anastomosis between the pubic branches of the 

 obturator and the external circumflex, and all gradations may be found between the normal ar- 

 rangement and the complete replacement of the original intrapelvic portion of the obturator by 

 the pubic anastomosis. 



The origin of the obturator from the deep epigastric artery ( Fig. 728) becomes of importance 

 from the fact that, in order to reach its point of exit from the pelvis, the obturator canal, the 

 vessel must come into intimate relations with the crural ring, and mav thus add an important 

 complication to the operation for the relief of femoral hernia (page 1775). There are three possi- 

 ble courses for the vessel in relation to the ring : (i) it may pass inward from its origin over the 

 upper border of the ring and then curve downward and inward along the free border of Gim- 

 bernat's ligament to reach the obturator canal ; (2) it may bend downward abruptly at its origin 

 and pass in an almost direct course to the obturator canal, passing over the inner surface of 

 the external iliac vein, and therefore down the outer border of the crural ring ; or (3) it may 

 pass directly across the ring. As regards the relative frequency of each of these courses it . is 

 interesting to note that, according to obser\'ations made by Jastschinski, the course along the 

 outer border of the ring is much the most frequent, occurring m 60 per cent, of cases, and being 

 more frequent in females than in males. The course across the ring occurs in about 22.5 per 

 cent, of cases, and is again more frequent in females than in males ; while the course along the 

 free edge of Gimbernat's ligament occurs in only 17.5 per cent, of cases, and is more common 

 in males than in females. The differences in the two sexes are associated with the differences in 

 the form of the pelvis and of the obturator foramen. 



Practical Considerations. — The gluteal and sciatic arteries have not uncom- 

 monly been affected by aneurism which has shown itself as a pulsating' compressible 

 tumor in the gluteal region, often with a bruit, and usually causing pain over the 

 nates, extending down the posterior aspect of the thigh — from pressure on the sciatic 

 nerve — and causing lameness. 



The gluteal aneurism is situated somewhat farther back in the buttock than the 

 sciatic, which is apt to be farther forward and downward, near the gluteo-femoral 

 crease (Agnew). 



Either of these vessels or the internal pudic may require ligature on account of 

 stab-wounds. Serious hemorrhage from a wound in the upper part of the gluteus 

 maximus, i.e., a little below a line from the posterior superior iliac spine to the top 

 of the great trochanter, is likely to proceed from the gluteal artery. Lower, nearer 

 to the fold of the buttock, it mav come from the sciatic. The gluteal may be tied 

 through an incision made along the line just mentioned, from the posterior superior 

 spine to the trochanter. With the thigh in inward rotation, the junction of the middle 

 with the upper third of that line indicates about the point where the gluteal artery 

 comes out through the sciatic notch. The fibres of the gluteus maximus are sepa- 

 rated, the muscle is relaxed by full extension of the thigh, and the upper bony margin 



