948 



THE NERVOUS SYSTEM 



relation, from above downward, with the following structures: the posterior sur- 

 face of the ischium and the nerve to the quadratus femoris, the gemellus superior, 

 obturator internus, gemellus inferior, quadratus femoris, and adductor magnus 

 muscles. 



Muscular branches are given off at the upper part of the thigh to the semi- 

 tendinosus, to the long head of the biceps femoris, to the semimembranosus, and to 

 the adductor magnus, and, about the middle of the thigh, a branch is furnished to the 

 short head of the biceps. The branch to the short head of the biceps is derived from 

 the peroneal (external popliteal) portion of the nerve, while all the other muscular 

 branches are given off by the tibial (internal popliteal) part. The semitendinosus 

 receives two branches, one which enters it above and another which passes into it 

 below its tendinous intersection. The nerve to the long head of the biceps descends 

 along the sciatic trunk and enters the middle of the deep surface of the muscle. 

 The nerves to the semimembranosus and adductor magnus arise by a common 

 trunk which divides into three or four branches. One branch ends in the adductor, 

 and the others are distributed to the semimembranosus. The branch to the adductor 



FIG. 694. A DISSECTION OF THE NERVES IN THE GLUTEAL REGION. 



(The gluteus maximus and gluteus medius have been divided near their insertions, and thrown 



upwards.) 



Inferior gluteal artery 



Gluteus maximus 



INFERIOR GLUTEAL NERVE 



Gluteal artery 



Gluteua 

 mediuB 



BRAXCII TO <,!.!'- 

 TEUH MAXIM I 'fi 



Tendon of obturator extern' 



I-ilHTKRIOR 



rrn.worx 

 KKSra 



Vastus externus 



Gluteus maximus 



magnus supplies only those fibres of the muscle which begin from the tuberosity of the 

 ischium and descend vertically to the internal condyle of the femur. 



At the apex of the popliteal space the two component parts of the common trunk 

 of the sciatic become distinct. The tibial nerve (internal popliteal), formed by 

 fibres from the anterior branches of the fourth and fifth lumbar and first, second, and 

 third sacral nerves, passes vertically through the popliteal space, descends through 

 the leg to a point midway between the internal malleolus and the most prominent 

 part of the inner tubercle of the os calcis, where it divides into its terminal branches, 

 the lateral plantar and the medial plantar nerves. The part of the nerve from the 

 point of bifurcation to the lower border of the popliteus muscle is sometimes called 

 the internal popliteal; the part of the nerve in the back of the leg being then designated 

 the posterior tibial nerve. In the upper part of the popliteal space the tibial (internal 

 popliteal) nerve lies relatively superficially, being covered dorsally by the skin and 

 fascia, while in the lower part of the space it is overlapped by the heads of the 

 gastrocnemius and is crossed by the plantaris. In the upper part of the space it lies 

 in front of the posterior femoral cutaneous (small sciatic) nerve and to the outer 



