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Show 1867.] MYOLOGY OF IGUANA TUBERCULATA. 795 Peroneus primus. This muscle (figs. 15, 16 & 18, P. 1) arises, by a strong tendon, from the summit of the outer side of the external condyle of the femur. Passing downwards, it becomes tendinous just below the outer malleolus, and ends in a tendon which is inserted into the peroneal border of the fifth metatarsal bone, a little above its middle. Behind the ankle its tendon expands into a broad, strong, ligamentous fascia, which binds down the flexor muscles, being attached internally to the internal margin of the hinder surface of the astragalus. Peroneus secundus. A muscle, somewhat larger than the preceding (figs. 15 & 16, P. 2), arises from the antero-external surface of the fibula for almost its entire length. It is inserted close above the insertion of the preceding muscle. Gastrocnemius. Two distinct muscles compose the gastrocnemius:- (1) The first of these (figs. 13, 17&18, G.L.) arises from the internal condyle of the femur, where it is closely connected with the insertion of the first part of the semimembranosus, which embraces it. It is also attached to the tibial margin of the tibia, close to the insertion of the semitendinosus. Passing downwards, it soon receives a strong tendon from the biceps, which tendon runs down just internal to its outer border. At the ankle it becomes aponeurotic, and constitutes the most superficial and external part of the plantar fascia. (2) The second head (figs. 13, 15 & 18, G. E.) arises from the femur, immediately above the external condyle. Below it becomes a large muscle, considerably greater than the inner head of the gastrocnemius, which latter passes down superficially to this second portion. Becoming aponeurotic at the ankle, it contributes to form the superficial plantar fascia, especially that part which underlies the three peroneal metatarsals, its fibres, indeed, appearing to form as it were perforated tendons to the third and fourth digits. Plantaris. This muscle is at its origin so intimately connected with the outer head of the gastrocnemius that it is with some hesitation that I describe it by a distinct name. About the middle of the leg it separates somewhat from the gastrocnemius externus, and thence widens to the ankle, where it receives a reinforcement of a few muscular fibres from the fifth metatarsal bone, in the distal end of the outer surface of which is implanted a tendon which passes along the peroneal edge of the muscle. In the sole this muscle appears as three fleshy bellies (fig. 18, P.LA.), which form the perforated tendons of the second and third digits, and perhaps of the hallux also. The popliteus arises from the tibial aspect of the head of the fibula, and is inserted into the posterior surface and tibial margin of almost the upper half of the tibia (figs. 16 & 18, Pp.). Flexor longus digitorum (tig. 16, F. P. D., and fig. 18, F. L. D.). This rather large muscle arises ( 1) partly, in common with the last, from immediately above the external condyle of the femur, (2) from the upper third of the posterior surface (or margin) of the fibula, and (3) from almost the upper half of the tibial side of the fibula. |