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Show 1899.] THE MYOLOGY OF THE EDENTATA. 329 Biceps.-Among the Bradypodidce, Bradypus is remarkable for possessing a humeral head. This was noticed in five specimens (1, 2, 3, 4, 5), and is described under that name by all five observers individually. In all these cases the head was large, and in all the insertion of the muscle was much blended with that of the brachialis anticus. W e must confess that we find it very difficult to give any general rule for determining when a slip coming from the anterior aspect of the humerus and more or less connected with both brachialis anticus and biceps should be regarded as a brachialis anticus internus and when a humeral head of the biceps. W h e n the connection is only with one muscle, as is sometimes the case, the task is comparatively simple. W e are not, in this instance, prepared to take a different line from the above-mentioned writers, and therefore, at least conditionally, adopt their terminology. In all the five animals above alluded to there was also a glenoid head, and one (2) in addition possessed a coracoid head, Avhich went to the fascia on the inner side of the forearm. The combined gleno-humeral muscle may be inserted into the radius or the ulna or both. In Cholcepus (8, 10) only the glenoid head is present, and is inserted partly into the radius partly into the ulna. In one specimen (8) part of the muscle joined the acromial deltoid. In the Myrmecophagidce, Myrmecophaga (11) has glenoid and coracoid heads, the latter rising from the position Avhich would be occupied by the coracoid process were it present; the glenoid or long head divides below, the more superficial fibres being inserted into the radius with the short head, Avhilst the deeper group join the brachialis anticus to be inserted into the ulna. Tbe description Avhich we have of the other tAvo specimens (12,13) seems to agree fairly accurately with the above. Tamandua (14, 15, 16) resembles Myrmecophaga, though Bapp describes a humeral head in addition, Avhich we believe, iu this case, is a part of the brachialis anticus. In Cyclothurus (17, 18, 19, 20, 21) only the glenoid origin is present and inserted into the radius and ulna, usually with the brachialis anticus. In the Dasypodidce two heads were present in four specimens (22, 23, 24, and an extra specimen) out of five recorded. In Tatusia (25, 26) aud Chlamydophorus (27) only the long head is present. In the Manidce the gleno-ulnar part of the muscle alone is present (29, 30, 31, 32, 33, 34). In Oryeteropus (35, 36, 37) the long head appears to be the only part represented. Brachialis anticus.-In the Bradypodidce the outer part of the muscle alone is usually present, and does not in all cases reach as high as the surgical neck of the humerus. It may or may not join the biceps before its insertion, which is into the radius or ulna or both. In our specimen of Bradypus (1) there was also an inner head, which was almost continuous with the coraco-brachialis. In the Myrmecophagidce the muscle is remarkable for its frequent fusion with the bicsps. W e can definitely state that iu this family the generalized mammaliau brachialis anticus rising from the back of the surgical neck of the humerus and winding round |
