OCR Text |
Show 328 MESSRS. B. C A. WINDLE AND F. G. TARSONS ON [Mar. 7, beloAv the lesser tuberosity of the humerus is specially marked off from the rest of the muscle. The name of subscapulo-humeral, Avhich sufficiently indicates its nature, has been suggested for this slip (1, 2, 5, 10). In one specimen of Bradypus (2) the sub-scapularis was divided into three parts, the hindmost of which was the subscapulo-humeralis. In Myrmecophaga Macalister (I.) found the muscle intersected by ten tendinous planes, and the specimen noAV in the B.C.S. Museum (11) shows the same condition. W e further found in this specimen that five separate nerves, all from the dorsal part of the brachial plexus, entered the muscle. Macalister states that there are two accessory slips to the muscle in this animal: (a) the subscapulo-humeralis, and (b) " a triangular slip from the fossa above the subscapular nerve." Pouchet (II.) found that the tendon of insertion split into upper and lower parts and between them Avas the short head of the biceps ; it is, hoAvever, just possible that he may have mistaken the upper edge of the supraspinatus, Avhich is very prominent in this animal, for part of the insertion of the subscapularis. In Tamandua (14) the muscle is also considerably broken up. In no other Edentate Avas any special feature of interest noted in connection with this muscle. Coraco-brachialis.-An Edentate characteristic of considerable interest is the great frequency of occurrence of the coraco-brachialis longus throughout tbe Order. In the Bradypodidce, Bradypus and Cholcepus, as is so often tbe ca^e, differ in their myology. In the former the coraco-brachialis medius alone is present (1, 2, 3, 4, 5, 6), and in our own specimen (1) we were careful to notice that the musculo-cutaneous nerve passed above the muscle, i. e. betAveen it and the bone. In Cholcepus (8,10) the brevis and longus alone were present,though Galton (X.)in another specimen says that he found only a thin cord-like middle variety. In the Myrmecophagidce, Myrmecophaga (11, 12) and Tamandua (14, 15, 16) have the longus only attached to the supracondylar arch, and given off from the short head of the biceps about the middle of the arm ; whilst in the four specimens of Cyclothurus of which Ave have records (17, 18, 20, 21) no coraco-brachialis at all was present. In the Dasypodidce the longus and brevis were present in two specimens of Dasypus (22, 23), but in another specimen described by Wood (Journ. of Anat. & Phys. i. p. 51), and in Cuvier and Laurillard's specimen (25), the longus only was found. In Tatusia the longus and brevis were present in one specimen (25), the longus only in another (26). In Chlamydophorus the muscle was totally absent in Hyrtl's specimen (28), whilst in Macalister's (27) tbe brevis was present. In the Manidce the muscle was totally absent in five specimens (29, 30, 31, 32, 34), but in one (33) the longus occurred. In Oryeteropus (35, 36, 37) the longus alone is present. From the above it will be seen that this muscle is very variable in its condition throughout the Order, not alone varying in different genera but in different specimens of the same animal. |