MUSCLES OF THE PELVIC LIMBS. 201 
the acetabulum, crosses the iliopsoas (d@) obliquely and has its 
Insertion by muscle-fibres into an elongated area (five milli- 
meters in length) on the shaft of the femur just distad of the 
lesser trochanter and between the insertion of the adductor 
femoris (g) and that of the vastus medialis (c). 
Relations.—The cranial edge forms part of the floor of the 
iliopectineal fossa. Lateral surface in relation with the iliopsoas 
(2) and vastus medialis (¢); medial surface with the adductor 
longus (/) and adductor femoris (g). 
Action.—Adductor of the thigh. 
M. quadriceps femoris.—The quadriceps femoris is a very 
powerful extensor muscle on the front of the thigh. It consists 
of four muscles which unite to form the great extensor of the 
shank. It is inserted into the patella and through it, by the 
ligamentum patelle, into the tibia. It may be compared to the 
triceps brachii. The parts are: 
(1) M. rectus femoris (Fig. 92, 4; Fig. 90, c). 
Origin by strong tendon from an elongated triangular area 
which has its base at the acetabulum and its apex about five 
to seven millimeters craniad of the acetabulum, along the ven- 
tral border of the ilium. The area is between that for the 
capsularis and that for the iliopsoas. The muscle is flat near its 
origin, but soon becomes a triangular prismatic mass which is 
united to the dorsal border of the vastus lateralis (Fig. go, @) 
at the junction of the middle and last thirds of the thigh. 
Insertion into the oblique area on the outer surface of the 
patella near its proximal border in connection with the vastus 
lateralis. 
Relations.—Outer or lateral surface at the origin with the 
gluteus minimus, the edge of the capsularis, the gluteus medius 
(Fig. 90, 4), and farther distad with the vastus lateralis (Fig. 
90, @). Medial surface with the tensor fascie late (Fig. 92, a), 
sartorius (Fig. 90, a), and vastus medialis (Fig. 92, c). Inner 
(caudal) surface with the vastus intermedius. 
(2) M. vastus lateralis (Fig. 90, d).—A flat triangular 
prismatic mass joined distally to the preceding. It covers the 
dorsal part of the lateral surface of the thigh. 
Origin from a triangular area on the dorsal and lateral sur- 
