GREAT SCIATIC NERVE 



825 



which emerge above the great sciatic nerve. The dorsal nerve passes backward 

 on the upper part of the sacro-sciatic hgament and divides into branches which 

 enter the biceps femoris; it supphes 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 

 nerve of 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- 



Sacral spines 



Aponeurosis 

 of lo?igissi- 

 mus dorsi 



Lumbar 

 vertebrm 



Coccygeal 

 vei tebrce 



Lateial sacro- I iZCP^^^Zi' 

 iliac hgnmi lit \ ^,f,^!)f^?^ j,^^ 



Sncro-tciat 

 ligament 



Tuht, 

 ischi 



Lesser Gemti- Anastomosis^ 

 sciatic lus between ob- 

 foramen turator and 



internal pudic 

 veins 



Mammillary 

 process 



Brandies of anterior gluteal artery 

 and nerve 



Ihaco-fi mural or lateral circumflex vessels 



■Acetabular fifisa 

 Acetabular notch 



— Pubic tubercle 



'^Obturator artery 

 ^Obturator internus 

 ''Obturator vein 



Fig. 658. — ^Vessels and Nebves on Pelvic Wall of Horse. 

 Nervus iscHadicua = great sciatic nerv^; n. glut. inf. = posterior gluteal nerve; n. pudendu3 = pudic nerve. (After 



Sciimaltz, 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 fiat 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 



