294 PROF. OWEN ON THE ANATOMY 



Gracilis (PI. XXXV. p). — On the inner side of the cruraus, but more superficially, 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 crureeus. 



Vastus internus (PI. XXXV. q). — 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 into 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 seve- 

 ral distinct portions, the chief of which correspond with the external and internal origins 

 of the same muscle in the Mammalia. The gastrocnemius externus (PI. XXXI. XXXII. r) 

 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 PI. XXXII., is lined by syno- 

 vial membrane, and supports the tendon of the hiceps cruris, which glides through it. 

 The carneous fibres of the external gastrocnemius come oflF 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 (PI. XXXII. fig. 2. r), 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 anticus : 

 the conjunction of the thickened tendons of the gastrocnemii with this deeper-seated layer 

 of ligamento-tendinous substance constitutes a trochlear sheath (PI. XXXV. r***) lined 

 by synovial membrane, through which the flexor tendons of the toes gUde. 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. 



