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Show 1890.] HELODERMA SUSPECTUM. 191 tions slender accessory slips, all of which are much the same as we found to be the case in the hand, and which has been quite fully discussed above. W e shall dwell more in detail upon these points when we come to describe further on the smaller and special muscles found in the sole of the foot. 111. Flexor accessorius.-Mivart describes a muscle, which is divisible into two parts, under this name in Lguana (P. Z. S. 1867, p. 797), but it is only its first part that in any way agrees with a muscle which I propose to call by this name in Heloderma. I find that it arises as a thin, small, fleshy muscle from the posterior aspect of the fibular ossicle of the co-ossified bones of the proximal row of the tarsus and to a limited extent from the adjacent surface of the distal end of the fibula. Soon forming a flat tendon it at once passes to the tarsal aspect of the tendon of the flexor longus digitorum,, where, at a point about opposite the proximal row of tarsal bones, it fuses with it, and thus, as will be seen, constitutes a true accessory muscle to this deep flexor. 112. Fexor brevis digitorum (perforatus).-This arises, semitendinous, from the dense transverse fascia of the ventral aspect of the ankle, and also from tbe corresponding surface of the fibular side of the fused ossicles of the proximal row of the tarsal elements. Radiating, it divides into five muscular bundles, which pass in proper order to the five toes ; the one belonging to the hallux being the smallest, while the one £>oing to the little toe is the largest. The short fasciculus that goes to the hallux is chiefly inserted into the proximal end of the first phalanx of that digit, and simply forms a tendinous tubular sheath through which passes the tendon of the deep flexor, and not a distinct insertional, perforated tendon as is the rule with this muscle in the case of the other toes. W e note here that the tendon of the deep flexor sends off an accessory slip to every joint as it passes to the distal phalanx for insertion. In the case of the little toe the arrangement is quite similar to what we have just described for the hallux, while the tendon of the deep flexor does not send off any accessory slips to the joints of this digit. With respect to the three middle toes, the arrangement of the insertional tendons of the deep and superficial flexors corresponds with the structure of the same parts as we described them for the manus. 113. Lumbricales.-So far as I can discover it is only the tendons of the deep and superficial flexors going to the three middle toes that are supplied with lumbrical muscles, and these are arranged very much as we found them in the hand of the reptile we have under consideration, having quite similar origins and insertions. Iu this connection we must observe another muscular slip: it arises from the distal surface of the fused ossicles of the proximal row of the tarsus, beneath the origin of the short flexor, and, passing forwards and inwards, it becomes inserted on to the plantar side of the broad tendon of the long flexor in the sole of the foot, before the former splits up to be distributed to the toes. 114. Flexor fibulo-tarsalis.-I find no muscle elsewhere described 14* |
