Part 47

Insertion of which is into a triangular area dorsad of the tip of the great trochanter.

Relations.--Outer surface with the gluteus medius (Fig. 90, b), the pyriformis (Fig. 163, 7), the great sciatic nerve (Fig. 163, a), and the gluteus maximus. Inner surface with the ilium, ischium, the capsularis, the caudal edge of the gluteus minimus (Fig. 163, 5), and the cranial edge of the obturator internus (Fig. 90, e).

Action.--Rotates the femur and abducts it so as to carry the foot outward.

=M. gluteus minimus= (Fig. 163, 5).--The gluteus minimus is a long triangular muscle beneath the middle of the gluteus medius (Fig. 90, b) and with its caudal border against or covering the cranial border of the gemellus superior (Fig. 163, 6), to which it is frequently closely united.

Origin from the ventral half of the ilium, from near its cranial end to a point midway between the posterior iliac spine and the spine of the ischium. The muscle ends in a strong flat tendon.

Insertion into an oval facet at the base of the dorsal surface of the great trochanter on its lateral side.

Relations.--Outer surface with the gluteus medius (Fig. 90, b) and at the caudal border with the gemellus superior (Fig. 163, 6). Inner surface with the capsularis and rectus femoris (Fig. 92, b).

Action.--Rotates the femur so as to carry the foot out.

=M. capsularis= (gluteus quartus, or epimeralis).--The capsularis is a small flat bundle of muscle-fibres which lies obliquely beneath the gluteus minimus (Fig. 163, 5) and gemellus superior (6) on the lateral or outer surface of the ilium.

Origin by fleshy fibres from the surface of the ilium over a triangular area between the origin of the rectus femoris (Fig. 92, b) ventrad, the gemellus superior (Fig. 163, 6) dorsad, and of the gluteus minimus (Fig. 163, 5) craniad and the acetabulum caudad. The muscle passes over the smooth surface of the ilium and the pubis ventrad of the acetabulum and then over the capsule of the joint.

Insertion by fleshy fibres for about one centimeter in the middle line on the dorsal surface of the femur distad of the great trochanter.

Relations.--Outer surface with the gluteus minimus (Fig. 163, 5), the gemellus superior (6), and the vastus lateralis (Fig. 90, d). Inner surface with the ilium, the rectus femoris (Fig. 92, b), the capsule of the joint, and the vastus medialis (Fig. 92, c).

Action.--Rotates the thigh so as to carry the foot inward, hence antagonizes the iliopsoas.

=M. gemellus inferior.=--The gemellus inferior is a flat triangular muscle situated just caudad of the gemellus superior and beneath the obturator internus (Fig. 90, e), so that it is seen on reflecting the latter

Origin from the dorsal one-half of the whole lateral surface of the ischium between the ischial spine and the ischial tuberosity. The fibres converge toward its insertion. The inner surface of the muscle is covered by a strong tendon.

Insertion into the inner surface of the tendon of the obturator internus (Fig. 90, e) by tendon- and muscle-fibres. Some of the muscle-fibres are inserted into the capsule of the joint.

Relations.--Outer surface with the obturator internus (Fig. 90, e). Medial surface with the ischium. Caudal border with the quadratus femoris (Fig. 90, f). Cranial border with the gemellus superior.

Action.--Abductor of the thigh. The muscle may be considered as a separate head of the obturator internus (Fig. 90, e).

=M. quadratus femoris= (Fig. 90, f).--The quadratus femoris is a short thick muscle connecting the ischial tuberosity (2) and the proximal end of the femur. It lies just caudad of the obturator internus (e) beneath the proximal end of the biceps femoris (Fig. 68, t).

The origin is by fleshy fibres from a considerable triangular area on the lateral surface of the ischium near the tuberosity. The area lies between the origin areas of the gemellus inferior, biceps, semimembranosus, and the obturator externus.

Insertion into the distal two-thirds of the ventral border of the great trochanter and about half the adjacent surface of the lesser trochanter.

Relations.--Outer surface with the tenuissimus (Fig. 90, g), the biceps (Fig. 68, t), the semitendinosus (Fig. 90, j), and the great sciatic nerve (Fig. 163, a). Caudal border with the semimembranosus (Fig. 90, i). Ventral border with the adductor femoris (Fig. 90, h); dorsal border with the obturator internus (Fig. 90, e) and gemellus inferior.

Action.--Extensor of the thigh and rotator of the femur so as to carry the foot inward.

=M. obturator externus.=--The obturator externus is a flat triangular muscle beneath the adductor femoris (Fig. 92, g).

Origin by fleshy fibres from the median lip of the obturator foramen and from both dorsal and ventral surfaces of the rami of the pubis and ischium adjacent to the lip. Also from the outer surface of the ramus of the ischium as far as the area for the quadratus femoris (Fig. 90, f). The fibres converge to a strong flat tendon.

a, M. sartorius; b, M. gluteus medius; c, M. rectus femoris; d, M. vastus lateralis; e, M. obturator internus; f, M. quadratus femoris; g, M. tenuissimus; h, M. adductor femoris; i, M. semimembranosus; j, M. semitendinosus; k, M. vastus intermedius; l, M. plantaris; m, m′, m″, M. gastrocnemius, outer head (m, part from the external sesamoid bone; m′, from the plantaris; m″, from the superficial fascia); n, M. tibialis anterior; o, M. soleus; p, M. extensor longus digitorum; q, M. peroneus longus; r, M. peroneus tertius (r′, its tendon); s, M. peroneus brevis; t, tendon of Achilles; u, M. extensor brevis digitorum. 1, great trochanter of femur; 2, tuberosity of ischium, with cut origin of M. biceps femoris; 3, patella; 4, calcaneus; 5, transverse ligaments; 6, lateral malleolus.]

Insertion into the proximal portion of the bottom of the trochanteric fossa.

Relations.--Ventral surface with the adductor femoris (Fig. 92, g). Dorsal surface with the pubis and ischium. Caudal border with the quadratus femoris (Fig. 90, f).