36 
able of the muscles which act upon the bones of the leg is that 
already alluded to as the most superficial of those on the outer 
side of the thigh, It has a broad, thin, triangular form, arises from 
the spines of the sacrum by a-strong but short aponeurosis which 
soon becomes fleshy; the carneous fibres converge as they descend*, 
and pass into a thin aponeurosis at the lower third of the thigh: 
this is closely attached to the muscles beneath (vastus externus and 
crureus), then spreads over the outer and anterior part of the knee- 
joint, is inserted into the patella, and into the anterior process of the 
head of the tibia. 
Owing to the great antero-posterior extent of the origin of this 
muscle, its anterior fibres are calculated to act as a flexor, its pos- 
terior ones as an extensor of the femur: all together combine to 
abduct the thigh and extend the leg, unless when this is in a state 
of extreme flexion, when a few of the posterior fibres glide behind 
the centre of motion of the knee-joint. 
Sartorius.—The origin of this muscle is proportionally as much 
extended as that of the preceding, with which it is posteriorly conti- 
nuous: it comes off aponeurotic, from the anterior and superior 
margin or labrum of the ilium; the fibres soon become fleshy, and 
the muscle diminishes in breadth and increases in thickness as it de- 
scends: it is inserted by short and strong tendinous filaments ob- 
liquely into the anterior part of the tendon of the broad rectus, and 
into the upper and anterior end of the tibia. Its insertion is partly 
covered by the internal head of the gastrocnemius. 
It bends and adducts the thigh, and extends the leg. 
Biceps flexor cruris.—This is a single muscle, corresponding with 
the preceding in the characteristic modifications of its extended ori- 
gin, in relation to the great antero-posterior development of the pel- 
vic bones. It is exposed by the removal of the broad rectus. Orig. By 
a broad and thin aponeurotic tendon, which at first is confluent with 
that of the rectus, but soon becomes distinct. Jns. The fleshy fibres 
converge as they descend along the back and outer part of the thigh, 
and finally terminate in a strong round tendon, which glides through 
a loop formed here principally by a splitting of the tendinous origin 
of the gastrocnemius externus, and is inserted into the process on the 
outside of the fibula one: inch from its proximal extremity. By 
means of the loopt the weight of the hinder parts of the body is 
partially transferred, when the leg is bent, to the distal end of the 
femur; and the biceps is enabled, by the same beautiful and simple 
* They are not divided into a superficial and deep layer, as in the Ostrich, 
but form a simple stratum, as in the Cassowary. Meckel regards the rectus 
as entirely wanting in the Cassowary, supposing the present muscle to be 
the analogue of the gluteus maximus and tensor vagine united. He says 
that Professor Nitzch observed a like absence of the rectus femoris in the 
Emeu. The muscle which these anatomists call the rectus in other birds, is 
astrip of the crureus, arising high up from the femur, and which in the 
Ostrich takes its origin from the os pubis. 
+ Which in the common fowl is formed chiefly by a ligament extended 
from the back of the outer condyle of the femur to the head of the tibia. 
