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Show 1901.] CHLAMYDOPHORUS TRUNCATUS. 115 not differ from previous descriptions, but it may be noted that the component tendons of the tendo Achillis showed no signs of the spiral twist around one another, that seems to occur to a greater or less extent among the generality of mammals l. The Plantaris (text-figs. 16 & 17, pi.), as in Dasypus2, has no direct attachment to the heel; its tendon passes through a foramen in the calcaneum (a gutter in Dasypus) and di\ ides in the sole of the foot into separate tendons inserted upon the proximal phalanges and the expanded navicular. The Peroneus longus and brevis (text-fig. 16, p.l. & p.br.) differ from the same muscles in the previously described specimens and in Tatusia by respectively rising partly from the knee-cap and external condyle of the femur as in Dasypus sexcinctus3. The peroneus longus rises from the outer side of the knee-cap and from the proximal part of the outer surface of the fibula; it is inserted as usual upon the base of metatarsal i. The Peroneus brevis and extensor brevis v. rise by a common origin from the external condyle of the femur, the external lateral ligament, and the proximal part of the antero-lateral surface of the fibula. The single belly terminates, in two delicate tendons, inserted respectively on the base of the metatarsal and of the penultimate phalanx of digit v. In view of the speculations that have arisen concerning the origin of the external lateral ligament as a modification of a femoral tendon of origin of the peroneus longus4, one might expect the origin of the peroneus brevis and extensor brevis v from the ligament itself as well as from the femur to throw some light upon the question, but apparently it does not. For, with the facts as they stand, it can be argued with equal propriety that the ligament in question is a structure originally independent of the muscle, but in this case serving as part of its area of attachment, or that it is part of the femoral tendon of origin of the muscle in process of transformation-functionally a ligament but not yet completely divorced from the muscle. The Tibialis anticus (text-fig. 16, t.a.) had an origin (not mentioned by Macalister) from the anterior inner border of the fibula. A similar origin is found in Dasypus, Cyclothurus, Bradypus, and Cholcepus5. The Tibialis posticus accessorius (text-fig. 17, t.p. n ) took origin from the proximal part of the hollow on the inner surface of the fibula, and was inserted upon the inner surfaces of the astragalus. According to Macalister's description, it rises from the tibia and is inserted on the entocuneiform. The Extensor digitorum communis (fig. 16, e.d.c.) sends a tendon 1 Parsons: "On the Morphology of the Tendo Achillis." Journ. Anat. & Physiol, xxviii. 1894, p. 414. 2 Galton, 1. c. p. 556. 3 Galton, 1. c. p. 559; also No. C 208, Physiol. Series, R. Coll. Surg. Museum. 1 Bland Sutton : ' Ligaments, their Nature and Morphology,' 1887, p. 34. 5 Macalister, 1. c. p. 268. Galton, 1. c. p. 558. 8* |
