MUSCLBS OF THE PELVIC LIMBS. 193 



Origin by numerous small separate heads from the dorsal 

 surface of the ramus of the ischium aloiifj 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 



Insertion 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, s; 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 vertebrcE. 



{b) The portion corresponding to the human iliacus arises 



/ fleshy fibres from the ventral border of the ilium, from 



^.^ osite the auricular impression to the iliopectineal eminence. 



he portions of the muscle all converge to form a conical 



ss which ends in a strong tendon lying on its outer sur- 



y 



