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Show 1884.] MR. G. E. DOBSON ON CAPROMYS MELANURUS. 245 obliquely into the distal third of the plantar surface of the first metatarsal bone on its inner side. Extensor hallucis longus is well developed, arising from the middle third of the shaft of the fibula and from part of the interosseous membrane, and is inserted into the terminal phalanx of the hallux. Peroneus longus, brevis, quartus, quinti digiti.-All these muscles are well developed, the p. longus arising as usual most superficially from the head of the fibula, the p. brevis under it by an extensive origin external to the lower third of the fibula, while, under cover of it and external to it, the p. quartus and p. quinti digiti ; all the tendons pass behind the malleolus and are inserted as usual. Extensor digitorum brevis is small, arising from the os calcis on the fibular side of the astragalus ; divides into two tendons, of which the inner unites with the long extensor tendon of the second toe ; the outer is inserted into the base of the second phalanx of the third toe. This muscle should, evidently, be considered a pedal part of the same mass from which the peroneus quartus and peroneus quinti digiti tendons are derived. Gastrocnemius is very large, having the usual origin and insertiou. Plantaris arises from the external condyle in close union for some distance with the gastrocnemius : its tendon passes over the os calcis and enters the foot, where it becomes continuous with the plantar fascia and gives part origin to the flexor digitorum brevis. Soleus has a fibular head only, arising from the head of the fibula. Flexor digitorum tibialis arises from the head of the fibula under cover of the popliteus, and between the internal margin of that muscle and the origin of the tibialis posticus, and from the shaft of the tibia, under cover of the popliteus, as far down as the commencement of its lower third ; forms a strong tendon which passes through a groove on the internal malleolus, on the fibular side of the tibialis posticus tendon, and, entering the foot, unites with the tibial side and superficial surface of the flexor flbalaris, forming the tendon for the hallux and contributing to that for the fifth toe. Tibialis posticus.-Smaller than the preceding, between which and the flexor fibularis it arises from the head of the fibula and along the upper half of the shaft of the tibia ; forms a moderately large tendon, which, passing across the internal malleolus on the tibial side of the tendon of the flexor tibialis, is inserted into the scaphoid bone. Flexor digitorum fibularis is of great size, arising from nearly the whole fibula, from the interosseous membrane, and from the middle third of the shaft of the tibia ; forms a strong tendon which unites with that of the flexor tibicdis, as described above1, and is distributed mainly to the three middle toes. Flexor digitorum brevis is very large, arising in two masses, a superficial and a deep : the former arises from the plantaris and 1 The relations and connexions of the above-described three muscles conform in all respects to the Hystricine type, as explained in the writer's paper, " O n the Homologies of the Long Flexor Muscles'of the Feet of Mammalia, with Remarks on the Value of their leading Modifications in Classification," Journ. Anat. & Phys. xvii. p. 142. |