

THE MUSCLES OF THE GLUTEAL REGION 477 



to the pelvic surface of the inferior ramus of the ischium, i. e., within the margin. 

 Both obturator muscles are connected with this membrane. 



The Obturator interims is situated partly within the lesser pelvis, and partly 

 at the back of the hip-joint. It arises from the inner surface of the antero-lateral 

 wall of the pelvis, where it surrounds the greater part of the obturator foramen, 

 being attached to the inferior rami of the pubis and ischium, and at the side to the 

 inner surface of the hip bone below and behind the pelvic brim, reaching from the 

 upper part of the greater sciatic foramen above and behind to the obturator fora- 

 men below and in front. It also arises from the pelvic surface of the obturator 

 membrane except in the posterior part, from the tendinous arch which completes the 

 canal for the passage of the obturator vessels and nerve, and to a slight extent from 

 the obturator fascia, w r hich covers the muscle. The fibers converge rapidly toward 

 the lesser sciatic foramen, and end in four or five tendinous bands, which are found 

 on the deep surface of the muscle; these bands are reflected at a right angle over 

 the grooved surface of the ischium between its spine and tuberosity. This bony 

 surface is covered by smooth cartilage, which is separated from the tendon by a 

 bursa, and presents one or more ridges corresponding with the furrows between 

 the tendinous bands. These bands leave the pelvis through the lesser sciatic fora- 

 men and unite into a single flattened tendon, which passes horizontally across the 

 capsule of the hip-joint, and, after receiving the attachments of the Gemelli, is 

 inserted into the forepart of the medial surface of the greater trochanter above 

 the trochanteric fossa. A bursa, narrow and elongated in form, is usually found 

 between the tendon and the capsule of the hip- joint; it occasionally communicates 

 with the bursa between the tendon and the ischium. 



The Gemelli are two small muscular fasciculi, accessories to the tendon of the 

 Obturator internus which is received into a groove between them. 



The Gemellus superior, the smaller of the two, arises from the outer surface of 

 the spine of the ischium, blends with the upper part of the tendon of the Obturator 

 internus, and is inserted with it into the medial surface of the greater trochanter. 

 It is sometimes wanting. 



The Gemellus inferior arises from the upper part of the tuberosity of the ischium, 

 immediately below the groove for the Obturator internus tendon. It blends with 

 the lower part of the tendon of the Obturator internus, and is inserted with it 

 it into the medial surface of the greater trochanter. Rarely absent. 



The Quadratus femoris is a flat, quadrilateral muscle, between the Gemellus 

 inferior and the upper margin of the Adductor magnus; it is separated from the 

 latter by the terminal branches of the medial femoral circumflex vessels. It arises 

 from the upper part of the external border of the tuberosity of the ischium, and is 

 inserted into the upper part of the linea quadrata that is, the line w r hich extends 

 vertically downward from the intertrochanteric crest. A bursa is often found 

 between the front of this muscle and the lesser trochanter. Sometimes absent. 



The Obturator externus (Fig. 436) is a flat, triangular muscle, which covers 

 the outer surface of the anterior w r all of the pelvis. It arises from the margin 

 of bone immediately around the medial side of the obturator foramen, viz., from 

 the rami of the pubis, and the inferior ramus of the ischium; it also arises from the 

 medial two-thirds of the outer surface of the obturator membrane, and from the 

 tendinous arch which completes the canal for the passage of the obturator vessels 

 and nerves. The fibers springing from the pubic arch extend on to the inner sur- 

 face of the bone, wiiere they obtain a narrow origin between the margin of the 

 foramen and the attachment of the obturator membrane. The fibers converge 

 and pass backward, lateralward, and upward, and end in a tendon which runs 

 across the back of the neck of the femur and lower part of the capsule of the hip- 

 joint and is inserted into the trochanteric fossa of the femur. The obturator vessels 

 lie between the muscle and the obturator membrane; the anterior branch of the 





