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Show 1866.] ON THE ANATOMY OF THE CRESTED AGOUTI. 399 part of the pectoralis major, we are led, as before stated, to regard it as a portion of the last-named muscle. The supraspinatus is larger in bulk than the infraspinatus. There is nothing unusual in its attachments. The infraspinatus stretches from the infraspinous fossa to the summit of the outer border of the great tuberosity of the humerus. The subscapularis is normal, but does not occupy the whole of the subscapular surface of the bone. Its condition approximates very much to that found in Hyrax*. The teres major arises from the upper half of the posterior margin of the scapula, and is inserted as usual, but in common with the latissimus dorsi. The teres minor has an origin from the inferior third of the posterior margin of the scapula; and its insertion is into the base of the tuberosity of the humerus. It is altogether very small and closely adherent to the infraspinatus. Meckelf seems to have failed in detecting this muscle in Rodents, possibly confounding it with the infraspinatus. The last-mentioned five scapular muscles present no further difference worthy of mention, either in the Guinea-pig, the Rabbit, or the Hare. The biceps has only a single head, and is inserted into the posterior border of the ulna by a strong tendon passing deeply between the muscles, and fixed to the ulnar side of the ridge immediately in front of the greater sigmoid cavity (fig. 2, B). According to Meckel % this muscle also goes to the ulna in the Porcupine and Beaver; we have found this also to be the case in the Guinea-pig, Rabbit, and Hare; there is the usual attachment of the superficial fascia in the forearm; and in addition a strong fibrous band unites it to the neck and shaft of the radius. The coraco-brachialis consists of two parts, the longer of which descends only to about the middle of the shaft of the humerus ; the short part is inserted above the tendon of the teres major§(fig.2, C.b.). In the Hare, Rabbit, and Guinea-pig this muscle does not descend so far down the shaft of the humerus as in D. cristata, and it is likewise less clearly, if at all, separable into two than in them. Meckel || considers it simple and short in the Hare, very long and strong in the Porcupine, and double in the Marmot. The brachialis anticus (figs. 2 & 3, B. a.) is peculiar in being divided into two distinct parts, one of which arises at the back of the head of the humerus, much as in Hyrax ^[, curving round the outside of the shaft. Its insertion is by a flattened tendon (much * P. Z. S. 1865, p. 338. t Loc. cit. p. 78. X Loc. cit. p. 288. § (Since the above was read, Mr. John W o o d has published a paper in the first number of the ' Journal of Anatomy and Physiology,' published at London and Cambridge, 1866. He therein proposes three names for the three portions of the coraco-brachialis. The two parts in the Agouti answer respectively to his coraoo-brachialis proprius and coraco-brachialis superior vel brevis (he. cit. pp. 48 & 49). || Loc. cit. p. 280. f P. Z. S. 1865, p. 339. |
