SCIATIC. 515 



the Gluteus Maximus, and divides into branches, which, supply the deep mus- 

 cles at the back of the hip. 



Within the pelvis it distributes branches to the Pyriforrnis, Coccygeus, and 

 Levator Ani muscles ; some haemorrhoidal branches, which supply the rectum, 

 and occasionally take the place of the middle hsemorrhoidal artery ; and vesical 

 branches to the base and neck of the bladder, vesiculee seminales, and prostate 

 gland. External to the pelvis, it gives off the coccygeal, inferior gluteal, comes 

 riervi ischiadici, muscular, and articular branches. 



The coccygeal branch runs inwards, pierces the great sacro-sciatic ligament, 

 and supplies the Gluteus Maximus, the integument, and other structures on the 

 back of the coccyx. 



The inferior gluleal branches, three or four in number, supply the Gluteus 

 Maximus muscle. 



The comes nervi ischiadici is a long slender vessel, which accompanies the 

 great sciatic nerve for a short distance; it then penetrates it, and runs in its 

 substance to the lower part of the thigh. 



The muscular branches supply the muscles on the back part of the hip, anas- 

 tomosing with the gluteal, internal and external circumflex, and superior per- 

 forating arteries. 



Some articular branches are distributed to the capsule of the hip-joint. 



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, Pyri- 

 formis, and Obturator Internus, and just previous to quitting that cavity a nu- 

 trient 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 Gluteus Minimus, and 

 subdivides 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. 



The llio-lumbar Artery ascends beneath the Psoas muscle and external iliac 

 vessels, to the upper part of the iliac fossa, where it divides into a lumbar 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 Internus, some offsets running 

 between the muscle and the bone, one of which enters an oblique canal to 

 supply the diploe, whilst others run along the crest of the ilium, distributing 

 branches to the Gluteal and abdominal muscles, and anastomosing in their 

 course with the gluteal, circumflex iliac, external circumflex, and epigastric 

 arteries. 



The Lateral Sacral Arteries (Fig. 294) are usually two in number on each 

 side, superior and inferior. 



The superior, which is of large size, passes inwards, 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, and escaping by the corres- 



