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Show 1903.] THE MUSCLES OF THE UNGULATA. 283 Plantar Region. Flexor brevis digitorum pedis.-This rudimentary structure has already been described with the plantaris, of which it is the continuation into the sole. The Accessorius is always absent, the only approach to it is a small fleshy bundle seen by Mivart and Murie in Hyrax and by ourselves in the O x (40). Deep Plantar Muscles.-In the Hippopotamus (1, 3) there is an abductor indicis, an abductor minimi digiti, and double-headed flexores breves for each toe. In the Suidae there is a greater suppression and evidently considerable individual variation. Lesbres (V.) describes only a few fleshy fibres on the outer and inner side of the foot, while Chauveau (II.) says that four interossei are present. In our specimen of Red River-Hog (11) we found one interosseus going to the tibial side of the medius, one to the fibular side of the annularis, and one to each side of the minimus, in addition to a feeble abductor minimi digiti. In the Peccary (14), on the other hand, there were only three muscles, that to the tibial side of the minimus being absent. In the rest of the Artiodactyla it is usual to find only two double-headed flexores breves, each head having a sesamoid bone developed in it; there are, however, no fleshy fibres in these structures. An exception is the Water- Chevrotain, in which Chatin (XL) describes four interossei, and from his figure there appears to be a double-headed fleshy flexor brevis to each toe. The increased development is not surprising when one remembers how large the lateral digits are in this animal. In the Tapir (61) we found a double flexor brevis to each toe, and Murie (XVII.) agrees with this but describes in addition two superficial muscles to the medius. In the Horse two tinterossei {sic) are described by Chauveau (II.) and Cunningham. Among the Subungulata the sole-muscles are more numerous ; Hyrax (75) has an adductor indicis and annularis on a superficial plane and deep to them three double flexores breves, while in addition to these there is an abductor indicis and quarti digiti. In Mivart and Murie's specimen all these were present as well as an adductor medii on the superficial plane. In the Elephant (85), Paterson and Dun found an abductor hallucis rising from the calcaneum, and a " flexor brevis digiti secundi," which comes from the tuber calcis and covers the long tendons entering the sole. There is some reason to think that this represents the flexor brevis digitorum of Man, save that its insertion is into the metatarso-phalangeal capsule instead of into the middle phalanx. The minimus has an abductor and a double-headed flexor brevis. The four interosseous spaces are well supplied with muscles which do not seem to be arranged as double-headed flexores breves. Without an accurate diagram it is difficult to say whether any of these belong to the more superficial adductor series of the mammalian foot, or whether they are |