BRANCHES OF THE INTERNAL ILIAC. 627 



iliac, turns upward and outward between the obturator nerve and lumbo-sacral 

 cord, to the inner margin of the Psoas muscle, behind which it divides into a lum- 

 bar and an iliac branch. 



The lumbar branch supplies the Psoas and Quadratus lumborum muscles, 

 anastomosing with the last lumbar artery, and sends a small spinal branch through 

 the intervertebral foramen, between the last lumbar vertebra and the sacrum, into 

 the spinal canal, to supply the spinal cord and its membranes. 



The iliac branch descends to supply the Iliacus muscle ; some offsets, running 

 between the muscle and the bone, anastomose with the iliac branch of the 

 obturator ; one of these enters an oblique canal to supply the diploe, whilst others 

 run along the crest of the ilium, distributing branches to the Gluteal and Abdom- 

 inal muscles, and anastomose in their course with the gluteal, circumflex iliac, 

 and external circumflex arteries. 



The Lateral Sacral Arteries (Fig. 372) are usually two in number on each side, 

 superior and inferior. 



The superior, which is of large size, passes inward, and, after anastomosing 

 with branches from the middle sacral, enters the first or second sacral foramen, is 

 distributed to the contents of the sacral canal in the same manner as the lateral 

 spinal branches from the vertebral, and, escaping by the corresponding posterior 

 sacral foramen, supplies the skin and muscles on the dorsum of the sacrum, anas- 

 tomosing with the gluteal. 



The inferior passes obliquely across the front of the Pyriformis muscle and 

 sacral nerves to the inner side of the anterior sacral foramina, descends on the 

 front of the sacrum, and anastomoses over the coccyx with the sacra media and 

 opposite lateral sacral arteries. In its course it gives off branches which enter 

 the anterior sacral foramina; these, after giving off branches to be distributed to 

 the contents of the sacral canal in the same manner as the lateral spinal branches 

 from the vertebral, escape by the posterior sacral foramina, and are distributed to 

 the muscles and skin on the dorsal surface of the sacrum, anastomosing with the 

 gluteal. 



The Gluteal Artery is the largest branch of the internal iliac, and appears to 

 be the continuation of the posterior division of that vessel. It is a short, thick 

 trunk, which passes out of the pelvis above the upper border of the Pyriformis 

 muscle, and immediately divides into a superficial and deep branch. Within the 

 pelvis it gives off a few muscular branches to the Iliacus, Pyriformis, and Obtu- 

 rator internus, and, just previous to quitting that cavity, a nutrient artery, which 

 enters the ilium. 



The superficial branch passes beneath the Gluteus maximus and divides into 

 numerous branches, some of which supply that muscle, whilst others perforate its 

 tendinous origin, and supply the integument covering the posterior surface of the 

 sacrum, anastomosing with the posterior branches of the sacral arteries. 



The deep branch runs between the Gluteus medius and minimus, and sub- 

 divides into two. Of these, the superior division, continuing the original course 

 of the vessel, passes along the upper border of the Gluteus minimus to the 

 anterior superior spine of the ilium, anastomosing with the circumflex iliac and 

 ascending branches of the external circumflex artery. The inferior division 

 crosses the Gluteus minimus obliquely to the trochanter major, distributing 

 branches to the Glutei muscles, and inosculates with the external circumflex 

 artery. Some branches pierce the Gluteus minimus to supply the hip-joint. 



Surface Marking. The position of the three main branches of the internal iliac, the 

 sciatic, internal pudic. and gluteal, which may occasionally be the object of surgical interference, 

 is indicated on the surface in the following way : A line is to be drawn from the posterior supe- 

 rior iliac spine to the posterior superior angle of the great trochanter. with the limb slightly 

 flexed and rotated inward : the point of emergence of the gluteal artery from the upper part of 

 the sciatic notch will correspond with the junction of the upper with tbe middle third of tbis 

 line. A second line is to be drawn from tbe same point to the middle of tbe tuberosity of the 

 ischium ; tbe junction of the lower with the middle third marks the point of emergence of the 

 sciatic and pudic arteries from the great sciatic notch. 



