OCR Text |
Show 1899.] THE MYOLOGY OF THE EDENTATA. 1003 base of the outermost metatarsal. In Cholcepus, Humphry (9) found the muscle as in Bradypus, but in another specimen (10) as well as in our own (8) it was not seen. In the Myrmecophagidce the muscle is present in Myrmecophaga (11, 12), Tamandua (14, 15), and Cyclothurus (19). In Dasypus (22 and another) among the Dasypodidce the muscle rose from the outer side of the fibula and from the external condyle. It is also present in Chlamydophorus (27, 28, 28 a). In the Manidce (29, 32, 33) and Orycteropodidce (35, '66) the muscle is present and normal. Peronei tertius, quarti et quinti digiti.-It is difficult, in reviewing the literature, to feel perfectly certain as to the identity of these muscles. Macalister (VII.) says " there is no trace whatever of a true peroneus tertius in any of the species examined, Chlamydophorus, Tatusia, Dasypus, Bradypus, Cholcepus, Oryeteropus, Pholidotus, Cyclothurus, or Tamandua. The muscles described as such by authors are, in reality, peronei quinti." W e have little doubt that Macalister is right in many cases, but we have some doubt as to whether the statement applies accurately to all, since we have seen and already described a typical peroneus tertius in Bradypus. The points which, in our opinion, enable a right decision to be arrived at in the case of a doubtful peroneus tertius or p. quinti digiti are (a) its nerve-supply ; (b) its relation to the ankle, whether anterior or posterior; (c) its insertion into the extensor tendon or into the metatarsal bone of a digit. Unfortunately many writers fail to give details on some of these points or on all of them, and for this reason any generalizations which we may venture to offer must be taken with a reservation. In the Bradypodidce a well-marked peroneus tertius, inserted into the base of ythe metatarsal bone, passing in front of the ankle, and supplied by the anterior crural nerve, was found. Meckel (XI.) and Mackintosh (XVI.) mention a peroneus quinti, which the latter says is inserted into the tuberosity of the outer metatarsal. In Cholcepus (9, 10) a peroneus tertius is described, Humphry (9) stating that it came from the front of the fibula and was inserted into the bases of the two outer metatarsal bones. The relation to the ankle is not mentioned, but from what we learn as to its origin and insertion we are inclined to agree as to the correctness of this denomination. It should be borne in mind that both Cholcepus and Bradypus have only three toes on the hind foot; so that a peroneus quinti is not, so far as we have learnt the lessons of mammalian myology, a muscle with which one would expect to meet. In the Myrmecophagidce the outer or fifth toe is always developed, and we find that both Myrmecophaga (11) and Tamandua (14) have a peroneus quinti digiti, but w*e have not been able to satisfy ourselves as to the absence or presence of this muscle in Cyclothurus. In the Dasypodidce the peroneus quinti is present in Dasypus (22 and another) and Chlamydophorus (27, 28 a). In the Manidce (29, 32, 33) we find no account of a peroneus quarti or quinti. In the Orycteropodidce (35, 36) all four peronei were present, viz., longus, brevis, quarti et quinti digitorum. |