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Show 190 DR. R. W . SHUFELDT O N [Apr. 1, (4) Arising from the next inner ossicle of the distal tarsalia, but not passing through the tendinous slips of the extensor longus digitorum, this has an insertion similar to the last, but here upon the second digit. (5) The fourth digit is similarly supplied, only in its case the fasciculus arises from the extreme end of the fibula, and it has likewise two lateral slips, one upon either side, inserted upon the dorsal aspect of its proximal phalanx, and these arise on either side from the bases of the proximal joints of the third and fifth digits. So it will be seen that not only in this, but in other particulars, the present muscle differs from the corresponding one in Lguana, as described for us by Mivart (P. Z. S. 1867, p. 794). 107. Popliteus.-Heloderma has this muscle comparatively very large. It arises from the tibial side of the fibula, for about its proximal fourth, and passing obliquely downwards and inwards is inserted into the shaft of the tibia for nearly the entire length of its fibular aspect. At the back of the leg, at its origin and for some way beyond, it is somewhat intimately attached to the flexor longus digitorum that covers it; while in passing to its insertion it fills in much of the interosseous space with its flat, triangular muscular expanse. 108. Peroneo-tibial.-Anteriorly, and belonging to the deep set, we have this interesting muscle. It spans the inter-tibio-fibular space below. Arising from the lower third of the shaft of the tibia, its fibres pass across to become inserted into the corresponding extremity of the shaft of the fibula. Behind, it is largely covered by the tibialis jiosticus, as the latter passes to its insertion. 109. Tibialis posticus.-As is commonly the case among Lizards, this muscle possesses a triangular form with its apex above. It arises from the inner aspect of the fibular shaft, tibiad, for the distal half of its extent. Its fibres converge as they pass downwards and inwards, and when near the tarsus they become strongly tendinous, which tendon is powerfully inserted into the tibial ossicle oi the co-ossified elements of the proximal row of the ankle. Over the lower part of the tibia, a firm fascia fuses with the tendon of this muscle, which there spreads out to cover to some extent the tarsal joint, to which it gives a certain strength and support. 110. Flexor longus digitorum (perforans).-Large and carneous in its upper part, this muscle arises from the posterior aspect of the external condyle of the femur ; from the posterior aspect of the proximal half of the shaft of the fibula; and from the tendon of the external head of the gastrocnemius muscle. It is also quite intimately attached to the underlying popliteus at its origin. From these several points the flexor longus digitorum, as a muscle of some considerable bulk, passes down the back of the leg to become, near the ankle, quite suddenly flat and then completely tendinous. It passes dorsad of the tendinous arch at the ankle, and in the sole of the foot splits into five small tendons, which are distributed, one to each, to the five pedal digits. Each perforates the tendons of the flexor brevis digitorum, after which they send to the joints of the toes as they go to their distal inser- |
