70 ANTHROPOLOGY. 
round, and covered by a great quantity of fat; this forms the fold of the 
nates. It arises from the posterior fifth of the crest of the ilium, from the 
rough surface between the crest and the superior semicircular ridge. of this 
bone, from the posterior surface of the sacrum, and from the sides of the 
coccyx. The flat and thick tendon of this muscle is inserted into a rough 
ridge, which leads from the trochanter to the linea aspera; also into the 
upper third of that line, and into the fascia lata. Use: to extend the thigh, 
to abduct and rotate it Cones and to support and extend the pelvis. and 
the trunk on the lower extremity. 
Gluteeus medius, triangular, and thinner than the last, arises from the 
three anterior fourths of the outer edge of the crest of the ilium, and from 
the surface of the ilium, and is inserted into the upper and outer part of the 
great trochanter, being also attached anteriorly to the tendon of the glutzus 
maximus. Use: to abduct and rotate the thigh, and to maintain the pelvis 
in equilibrium on the femur. 
Gluteus minimus arises from the inferior semicircular ridge on the - 
dorsum of the illum, and from the rough surface between it and the edge 
of the acetabulum. The fibres converge and end in a strong, round, 
twisted tendon, which is inserted into the upper and anterior part of the 
great trochanter. Use: similar to the last. It also strengthens the ilio- 
femoral articulation. 
Pyriformis is a flattened triangular muscle, the base at the sacrum | 
within the pelvis, the apex at the trochanter. It arises within the pelvis, 
and is inserted into the upper part of the digital fossa at the root of 
the great trochanter. Use: to abduct the thigh, to extend and rotate it 
outwards. 
Gemelli, two smaller muscles, placed behind the ilio-femoral articulation, 
between the ischium and trochanter. The superior arises from the spine 
of the ischium, and is inserted into the upper part of the digital fossa of the 
great trochanter. The inferior arises from the upper part of the tuber ischn, 
and is also inserted into the digital fossa. Use: to rotate the thigh outwards 
and to abduct it. 
Obturator internus is situated partly within the pelvis and partly behind 
the ilio-femoral articulation. It arises within the pelvis from the superior 
surface of the thyroid ligament and from the circumference of the thyroid 
foramen, and is inserted into the digital fossa of the great trochanter. Use: 
to abduct and rotate the thigh outwards; also to act on the capsular 
hgament. 
Quadratus femoris arises from the external surface of the tuber ischu, 
anterior to the tendon of the semi-membranosus. It is inserted into the 
inferior and posterior part of the great trochanter, and into the posterior 
inter-trochanteric line. Use: to abduct and rotate the thigh outwards. 
Obturator externus, situated at the upper, posterior, and internal portion 
of the thigh, arises from the inferior surface of the thyroid or obturator 
ligament, and from the surrounding surfaces of the pubes and ischium. It 
is inserted into the lower part of the digital fossa. Use: to adduct the 
thigh and rotate it outwards. 
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