Part 43

Insertion.—By a thin, flat tendon upon the outer part of the shaft of the femur below the trochanter and at about the juncture of the upper and middle third of the bone.

FIG. 24.—Second layer of muscles of the thigh of a cock. Outside view. 1, Appendico-costales. 2, Levatores costarum. 3, Sacro-lumbalis. 4, Longissimus dorsi. 5, Intercostales. 6, Longissimus dorsi. 7, Latissimus dorsi. 8, Femoro-caudal. 9, Edge of obturator externus. 11, Gluteus medius. 12, Gluteus minimus. 13, Crureus. 14, Vastus externus. 15, Extensor femoris. 16, Biceps flexor cruris. 17, Semimembranosus. 18, Adductor magnus. 19, Adductor longus. 20, External abdominal oblique. 21, Depressor coccygis. 22, Tibialis anticus. 23, Tibialis posticus. 24, Flexor perforans digitorum profundus. 25, Flexor perforatus medius secundus pedis. 26, Flexor longus hallucis. ]

Shape.—Long, narrow, spindle-shaped, flattened from side to side.

Relations.—Interiorly to the obturator externus, and along the upper border of the long adductors of the thigh and the semimembranosus.

Action.—Pulls the tail down and to one side.

=Obturator Externus= (Fig. 24, No. 9). Location.—External posterolateral side of the pelvis.

Origin.—From the posterior half of the periphery of the ischiatic foramen and the concavity found on the external surface of the lateral part of the pelvis.

Insertion.—The fibers pass across to the femur and are inserted by a broad, flat tendon to the shaft of the femur just below the trochanter.

Shape.—Thick, fleshy.

Relations.—Lies just above the femoro-caudal muscle, the sciatic nerve and femoral artery pass over and external to its tendon.

Action.—Pulls the head of the femur backward.

=Obturator Internus= (Fig. 16, No. E, 1). Location.—Occupies the space between the ischium and the pubis.

Origin.—From the ventral surface of the ischium, including the posterior border, from the inner line of the corresponding post-pubis, and from the membrane covering the space between these two bones.

Insertion.—Becoming dense, subcylindrical, and strong, it passes through the obturator foramen and is inserted to the outer part of the trochanter of the femur, in common with the gemellus and opposite to the insertion of the gluteus medius.

Shape.—Subtriangular and flat with a central tendon; bipenniform.

Relations.—Outside the pelvis the tendon lies upon the gemellus and is external to it. Fills the obturator foramen and the space between the ischium and the pubis.

Action.—Acts as a posterior stay to the head of the femur.

=Gemellus= (Fig. 25, No. 5). Location.—Posterior to the head of the femur.

Origin.—From the fossa between the acetabulum and the obturator foramen, and on the outer side of the pelvis.

Insertion.—Its fibers are attached by fascia to the tendon of the obturator internus, and pass directly to the trochanter of the femur where they insert in common with that of the obturator internus.

Shape.—Strong, thick, chunky.

Relations.—Postero-external to the head of the femur.

Action.—Like the two preceding, when the head of the femur is fixed, it pulls the pelvis forward and steadies it on the head of the femur.

=Adductor Longus= (Fig. 24, No. 19). Location.—In the posterior femoral region.

Origin.—From a line on the lateral part of the pelvis.

Insertion.—The fibers, passing downward and forward, are inserted on a longitudinal line along the posterior part of the shaft of the femur.

Shape.—Broad, flat, fleshy.

Relations.—Posteriorly to the femur, and anteriorly to the adductor magnus.