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mechanism, to effect a more rapid and extensive inflection of the leg 
than it otherwise could have produced by the simple contraction of 
its fibres. 
Semimembranosus.—Origin. From the side of the coccygeal ver- 
tebre, and from the posterior end of the ischium ; it crosses the 
superficial or internal side of the semitendinosus. Ins. Into the fascia 
covering the gastrocnemius and the inside of the tibia. 
Semitendinosus.—This muscle arises from the posterior and outer 
part of the sacrum and ischium: it is a flattened triangular muscle, 
which receives the square accessorius muscle from the lower and 
posterior part of the femur. It gradually diminishes as it descends, 
and having passed the knee-joint, sénds off at right angles a broad 
and square sheet of aponeurosis, which glides between the two ori- 
gins of the gastrocnemius internus, and is inserted into the lower part 
of the angular ridge continued from the inside of the head of the 
tibia. The terminal tendon, continued from the apex of the muscle, 
then runs along the outer or fibular margin of the internal head of 
the gastrocnemius, and becomes confluent with the terminal tendon 
of that muscle. 
Crureus.—This is a simple but strong muscle: it commences at 
the upper and anterior part of the thigh by two extremities, of which 
the outer and upper one has its origin extended to the base of the 
trochanter; the inner and inferior comes off from the inner side of 
the femur, beneath the insertion of the gluteus magnus ; the two por- 
tions blend into one muscle much earlier than in the Ostrich. 
Gracilis.—On the inner side of the crureus, but more super- 
ficially, lies a narrow, compressed, long muscle, which rises by two 
heads, one from the anterior and upper part of the femur, the other 
from the os pubis ; both soon become blended together and transmit 
a broad thin tendon to be inserted into the lower and lateral part of 
the patella with the erureus. 
Vastus internus.—Two other muscles succeed the preceding, and 
rise beneath it from the inner and anterior part of the femur; they 
have a similar insertion, and obviously represent the vastus internus. 
The fibres converge to a middle aponeurosis, which increases to a 
strong short tendon, inserted into the upper and anterior projection 
of the tibia. 
Popliteus.—This small muscle is brought into view when the super- 
ficial muscles of the leg which are inserted into the foot are re- 
moved. Its carneous fibres extend from the fibula inwards and down- 
wards to the tibia. It is of relatively smaller extent than in the 
Cassowary. 
Gastrocnemius.—This consists, as in other birds, of several distinct 
portions, the chief of which correspond with the external and inter- 
nal origins of the same muscle in the Mammalia. The gastrocne- 
mius externus has two strong, narrow, rather flattened tendinous 
origins, which are attached, one about a line below the other, to the 
external ridge above the outer condyle of the femur; they are 
continued into each other about an inch below their bony attach- 
ments, and thus form a loop or pulley (lined by a synovial sheath) 
