GREAT SCIATIC NERVE 825 
which emerge above the great sciatic nerve. The dorsal nerve passes backward 
on the upper part of the sacro-sciatic ligament and divides into branches which 
enter the biceps femoris; it supplies a branch to the posterior part of the middle 
gluteus, and a nerve which turns around the posterior border of the latter and enters 
the posterior head of the superficial gluteus. The ventral nerve runs downward 
and backward on the sacro-sciatic ligament and divides into the posterior cutaneous 
nerveof the thigh (N. cutaneus femoris caudalis) and muscular branches which 
supply the semitendinosus. The former passes through the biceps femoris, emerges 
between that muscle and the semitendinosus at or a little below the level of the tuber 
ischii, and ramifies subcutaneously on the lateral and posterior surfaces of the hip 
and thigh (Fig. 657). The deep part of the nerve is connected by filaments with 
the pudic nerve. 
GREAT SCIATIC NERVE 
The great sciatic nerve (N. ischiadicus) (Figs. 574, 580, 658), the largest in 
the body, is derived chiefly from the sixth lumbar and first sacral roots of the lumbo- 
A poneurosis 
of longissi- 
mus dorsi 
—_——~. 
Sacral spines 
Lumbar 
verltebre 
Coccygeal 
vertebre 
Lateral sacro- { ~ 
diac ligament \ 
Sacro-sciatic 4 
ligament : 
Mammillary 
: process 
Tlio-lumbar vessels 
Branches of anterior gluteal artery 
and nerve 
Iliaco-femoral or lateral circumflex vessels 
—Acetabular fossa 
~~~ Acetabular notch 
: ee 
ii 
| Lesser Geimel- Anastomosis 
| sciatic — lus between ob- 
foramen turator and 
| internal pudic 
veins 
Pubic tubercle 
Obturator artery 
Obturator internus 
Obturator vein 
Fic. 658.—VesseELs AND Nerves on Petyic Watt or Horse. 
Nervus ischiadicus =great sciatic nerve; n. glut. inf.=posterior gluteal nerve; n. pudendus =pudiec nerve. (After 
Schmaltz, Atlas d. Anat. d. Pferdes.) 
sacral plexus, but usually has a fifth lumbar root and may receive a fasciculus from 
the second sacral nerve. It emerges through the greater sciatic foramen as a 
broad flat band which is blended at first with the posterior gluteal nerve and 
passes downward and backward on the lower part of the sacro-sciatic ligament and 
on the origin of the deep gluteus muscle. It turns downward in the hollow between 
