MUSCLES OF THE PELVIC LIMBS. 193 
Origin by numerous small separate heads from the dorsal 
surface of the ramus of the ischium along its symphysis and 
following its medial border from the symphysis nearly to the 
tuberosity. The fibres form a flat muscle which narrows and 
passes through the lesser sciatic notch, turns ventrad and ends 
in a strong flat tendon whose 
Jusertion is into the bottom of the trochanteric fossa of the 
femur. The tendon is continued proximad on the inner surface 
of the muscle and forms a smooth firm surface by which the 
muscle glides over the dorsal border of the ischium. Into the 
inner surface of this tendon near its insertion the tendon of the 
gemellus inferior is inserted. 
Relations.—Medial surface within the pelvis with a mass of 
fat.separating it from the pelvic organs. Dorsal or outer sur- 
face with the biceps femoris, the tenuissimus, the caudofemora- 
lis, and the great sciatic nerve. Inner surface with the ischium 
and the great sciatic nerve. Caudal (or ventral) border with 
the quadratus femoris. 
Action.—Abductor of the thigh. 
M. iliopsoas (Fig. 162, 8; Fig. 91, c).—The iliopsoas 
(equivalent to the human psoas and iliacus) is a conical muscle 
emerging from the abdominal cavity onto the medial surface of 
the femur. 
Origin.—(a) The portion corresponding to the human psoas 
(Fig. 162, 8) arises by ten vertebral heads. The first five of 
these come from the five cranial tendons of origin of the psoas 
minor (Fig. 162, 9); the sixth from a tendinous expansion 
which passes from the tendon of the first head over the ventral 
longitudinal muscles to. the transverse process of the fifth 
lumbar vertebra. The seventh, eighth, ninth, and tenth heads 
arise by fleshy fibres from the ventral surfaces of the centra of 
the last four lumbar vertebra. 
(6) The portion corresponding to the human iliacus arises 
by fleshy fibres from the ventral border of the ilium, from 
opposite the auricular impression to the iliopectineal eminence. 
The portions of the muscle all converge to form a conical 
mass which ends in a strong tendon lying on its outer sur- 
face. . 
‘th 
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