MUSCLES OF THE POSTERIOR LIMBS. 357 



Attachments. — Above, to the inferior surface of the ischium, iu front of the 

 ischial tuberosity — origin ; terminating, below, on the linear imprint on the 

 posterior face of the femur, a little below the trochanter internus (Fig, 

 ]'»7, 10). 



Rplations. — In front with the posterior face of the femur and external 

 obturator. Behind, and inwardly, with the adductor magnus. Outwards, with 

 the sciatic nerves and the gemellus posticus. 



Action. — It is an extensor and adductor of the femur. In our opinion, its 

 mode of attachment will not permit it to rotate this bone either inwards or out- 

 wards — at least in Sohpeds. 



• 

 7. Obturator Externus (Fig. 196, 13). 



Syiwnym. — Suhpubio-trochanteriua externus — Girard. 



Form — Structure — Situation — Direction. — A short, thick, flat muscle, tri- 

 angular, fasciculated, fleshy and aponeurotic, very delicate in texture, and 

 placed almost horizontally beneath the pelvis, at the margin of the obturator 

 foramen, which it covers, and from which it derives its name of obturator. 



Attachments. — 1. To the inferior surface of the pubis and ischium, by the 

 internal extremities of its fasciculi — -fixed inseiiion. 2. To the trochanteric fossa, 

 by the external extremities of these fasciculi — movable insertion. 



Belations. — Inferior ly, with the pectineus, the two adductors of the thigh, 

 and the quadratus femoris ; superiorly, with the capsule of the hip-joint, and 

 the internal obturator. 



Action. — An adductor and rotator outwards of the thigh. 



8. Obturator Internus (Figs. 196, 197). 



Synonym. — Subpubio-troclianterius intern us — Giro rd. 



Situation. — This muscle is situated in the pelvic cavity, above the oval 

 foramen, and is, consequently, opposite the external obturator. 



Form — Structure — Attachments. — It is formed of two portions. One is very 

 thin, and composed of slightly tendinous, divergent muscular fasciculi, which 

 arise from around the obturator foramen, are directed outwards, and terminate 

 in a tendon belonging to the other portion. The latter, elongated and penni- 

 form, is situated in the pelvis, and extends from the anterior angle of the 

 sacrum to the inferior extremity of the femur, following the direction of the 

 ischial border of the ilium, into which it is inserted. The tendon to which it 

 owes its penniform shape is inflected outwards, behind the supra-cotyloid crest 

 or sciatic ridge, joins the gemelli, and terminates in the bottom of the tro- 

 chanteric fossa. 



Bdations. — In its intra-pelvic portion, this muscle responds : outwards and 

 downwards, to the ilium, pubis, ischium, and external obturator ; inwards and 

 upwards, to the peritoneum, important vessels and nerves, and to a fibrous layer 

 that separates it from the bladder. In its extra-pelvic portion, it is in relation 

 with — behind, the middle gluteal muscle and the sciatic nerves ; in front, with 

 the gemelli. A synovial sheath facilitates the gliding of its tendon in the groove 

 in which it turns. 



Action. — It is a rotator of the thigh outwards, and, contrary to the opinion of 

 the majority of authors, we believe it to produce abduction rather than adduc' 



