58 
Gracilis (Pl. XIV. v).—On the inner side of the erureus, but more superficially, les 
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 crureus. 
Vastus internus (Pl, XIV. a).—Two other muscles succeed the preceding, and rise 
beneath it from the inner and anterior part of the femur; they have a similar inser- 
tion, and obviously represent the vastus internus. The fibres converge to a middle apo- 
neurosis, 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 superficial muscles of 
the leg which are inserted mto the foot are removed. Its carneous fibres extend from 
the fibula inwards and downwards to the tibia. It is of relatively smaller extent than 
in the Cassowary. 
Gastrocnemius.—This complex and powerful muscle consists, as in other birds, of 
several distinct portions, the chief of which correspond with the external and internal 
origins of the same muscle in the Mammalia. The gastrocnemius externus (Pl. X. XI, x) 
arises by a strong, narrow, rather flattened tendon (r*) from the ridge above the external 
condyle of the femur, which, about an inch below its origin, becomes firmly attached to 
the strong ligamentous loop attached by one end to the femur above the preceding ten- 
don, and by the other to the outer ridge of the fibula. This trochlear loop, which is dis- 
played by reflecting down the tendon of the gastrocnemius in Pl. XL, is lined by syno- 
vial membrane, and supports the tendon of the biceps cruris, which glides through it. 
The carneous fibres of the external gastrocnemius come off from the outer side of the 
tendon, and from the fascia covering the outer surface of the muscles of the leg: they 
are continued in a somewhat penniform arrangement two-thirds down the leg, upon the 
inner surface of the muscle, where they end in a strong subcompressed tendon. This 
joins its fellow-tendon, from the internal gastrocnemius, behind the ankle-joint, and both 
expand into a thick, strong ligamentous aponeurosis (Pl. XI. fig. 2. x), which extends 
over three-fourths of the posterior part of the tarso-metatarsal bone. The lateral margins 
of this fascia are bent down under the flexor tendons behind the joint, and become con- 
tinuous with a strong ligamentous layer gliding upon the posterior surface of the distal 
condyles of the tibia, and attached to the tendons of the peroneus and tibialis unticns - 
the conjunction of the thickened tendons of the gastrocnemii with this deeper-seated layer 
of ligamento-tendinous substance constitutes a trochlear sheath (PI. XIV. x***) lined by 
synovial membrane, through which the flexor tendons of the toes glide. The synovial 
membrane of the ankle-joint is continued upwards half an inch above the articular surface 
of the bone, between it and the fibro-cartilaginous pulley. Below the joint the margins 
are inserted into the lateral ridges of the tarso-metatarsal bone, becoming gradually 
thinner as they descend, and ending below in a thin semilunar edge directed downwards. 
