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Show 1867.] MYOLOGY OF IGUANA TUBERCULATA. 789 physis (figs. 14, 16, 17 & 18, Si). It is slightly connected, at its origin, with the first part of the iliacus, and some fibres spring from the brim of the pelvis just below the tendon of the rectus femoris. Passing downwards between the rectus femoris and the adductor, and passing peronead of the first part of the semimembranosus, it goes very deeply into the popliteal space (between the two heads of the gastrocnemius), and, uniting with the second part of the semimembranosus, is inserted by a tendon into the peroneal side of the head of the tibia above and behind the insertion of the tendon of the biceps. This muscle is easily separable longitudinally into two parts. Semimembranosus. This muscle consists of two portions so distinct in insertion that they may well be considered two separate muscles:- (1) The first portion (figs. 14, 15, 17 & 18, S. M. 1) arises from the tuberosity of the ischium, and from the tendinous arch which passes from the posterior end of the ilium to the spine of the pubis. Its origin is nearly in the same vertical line as, though ventral to, the common origin of the biceps and semitendinosus. Thick and fleshy, it is inserted into the back of the leg, embracing the inner head of the gastrocnemius, some fibres passing beneath the internal lateral ligament, while others extend along the posterior margin of the summit of the tibia. (2) The second portion (figs. 15, 17 & 18, S. M. 2) arises in common with the first portion, and is inserted by a tendon (common to it and to the tibial adductor) into the summit of the peroneal surface of the tibia. The semitendinosus (figs. 14, 17 & 18, S. T.) springs in common with the biceps from the strong tendinous arch just mentioned as passing from the posterior end of the ilium to the spine of the pubis, behind and a little above the tuberosity of the ischium. It is inserted by a strong tendon, common to it and to the gracilis, into the inside of the upper part of the tibia, at the lower end of the internal lateral ligament. The insertion is mainly superficial to the last-mentioned ligament; but a few tendinous fibres appear to pass inside it. Biceps (figs. 15, 17 & 18, B.F.). This arises, in common with the muscle last described, from the strong ligamentous arch passing from the ilium to the spine of the pubis, and arching over the great femoro-caudal tendon. It is inserted by a slender tendon, which o-oes very deeply into the popliteal space (between the two heads of the gastrocnemius), and, passing between the tibia and fibula, is inserted into quite the anterior aspect of the outer (peroneal) side of the tibia a little below its upper margin and below and in front of the insertion of the tendon common to the second part of the semimembranosus and the tibial adductor. The biceps becomes intimately united with the gastrocnemius, as it gives off a strong tendon (fig. 18), which runs down just internal to the outer border of the inner head of that muscle. Ilio-peroneal (figs. 15, 16, 17 & 18,1 P.). A long and strong muscle, which arises from the posterior part of the outer side of the ilium, covered by the posterior portion of the tendinous origin of the |
