372 PRACTICAL ANATOMY. 



middle and the inferior curved gluteal lines ( Fig. 226), from the capsule of the hip, 

 and is inserted into the anterior border of the greater trochanter. (Fig. 228.) The 

 nerve-supply is from the superior gluteal. (See page 28 1, Superior Gluteal Nerve.) 



Notice the common origin of the long head of the biceps and semitendin- 

 osus from the tuber of the ischium. (Fig. 226.) See where the semimem- 

 branosus, in its origin from the tuber, crosses the two preceding muscles since 

 it arises from the upper and outer part of the tuberosity. 



Greater Sacro-sciatic Foramen. The notch of the same name (Fig. 226) 

 is converted into this foramen by the lesser sacro-sciatic ligament. It transmits 

 the pyriformis muscle, which divides the foramen into an upper and a loweY com- 

 partment. (Fig. 258.) Above the muscle emerge the superior gluteal artery and 

 nerve : below the muscle, the greater sciatic nerve, the lesser sciatic nerve, the 

 sciatic artery, the internal pudic nerve and artery, and the inferior gluteal nerve. 



The pyriformis muscle arises from the anterior surface of the sacrum, be- 

 tween the four upper anterior sacral foramina. The muscle leaves the pelvis by 

 the greater sacro-sciatic foramen, and is inserted into the upper border of the 

 greater trochanter. 



The Gluteal Artery (Fig. 258). The largest branch of the internal iliac; 

 leaves the pelvis by the greater sacro-sciatic foramen, above the pyriformis, 

 divides into a superficial and a deep branch. The former lies between the gluteus 

 maximus and niedius, and anastomoses with the circumflex iliac brancli of the 

 external iliac artery ; the latter the deep branch lies between the gluteus 

 medius and minimus, and anastomoses with the external circumflex artery, a 

 branch of the profunda. 



The superior gluteal nerve a branch of the lumbo-sacral cord of the sacral 

 plexus accompanies the artery of like name (Fig. 258) and supplies the gluteus 

 medius and minimus and the tensor vagina; femoris. 



o 



The Sciatic Artery (Fig. 258). A branch of the internal iliac. It leaves 

 the pelvis below the pyriformis muscle. It gives branches to the rectum, base 

 of bladder, seminal vesicles, prostate, and all the muscles of the pelvic floor. 

 It sends branches to the muscles on the back of the hip ; one branch, the comes 

 nervi isc/iiadici, to the great sciatic nerve. (Fig. 258.) It anastomoses with the 

 gluteal, the obturator, both circumflex arteries, internal and external, and with 

 the superior perforating artery, a branch of the profunda femoris. 



The Great Sciatic Nerve (Fig. 193). The largest branch of the sacral 

 plexus. Leaves the pelvis below the pyriformis. Lies upon successively the 

 superior gemellus, the internal obturator, the inferior gemellus, the external 

 obturator, the quadratus femoris, and the adductor magnus. (Fig. 258.) It ends 

 in the popliteal space, in the internal and external popliteal nerves. It gives 

 motor branches to the biceps, semitendinosus, semimembranosus, and adductor 

 magnus muscles. It gives to the hip-joint articular brandies, which perforate 

 the posterior part of the capsule. 



The Small Sciatic Nerve (Fig. 260). A branch of the sacral plexus. 

 (Fig. 193.) It leaves the pelvis below the pyriformis muscle, lying behind the 

 greater sciatic nerve. Its branches are cutaneous : ascending, internal, external 

 and descending. The latter passes through the popliteal space to supply the 

 skin over the insertion of the flexors. of the leg. (Fig. 255.) The small sciatic 

 is then the great divorced sensory branch of the great sciatic, carrying out 

 Hilton's law. The internal branches of this nerve are numerous. (Fig. 260.) 

 The short ones supply the skin on the inner side of the thigh ; the longest one 

 of the internal branches is called the inferior pudendal, or nerve of Soemmering, 

 and supplies the scrotum and labia majora. 



How to find the long pudendal in practical anatomy : It crosses the tendons 

 of the biceps and semitendinosus, on the tuber of the ischium. (Fig. 260.) 



