OCR Text |
Show 14 MR. F. E. BEDDARD ON THE [Jan. 6, (8) In addition to the biceps there was a very remarkable muscle present which I have once before observed ; unfortunately I have no note of the bird in which it occurred. This muscle is a kind of accessory biceps: it arises from the humerus just below the insertion of the deltoid by a tendinous sheet; in the specimen before me, as shown in the drawing (fig. 2, Bi.2, p. 13), the muscle was prolonged forwards, running parallel to the fibres of the deltoid and closely embracing the nerve (N.) which supplies this part of the wing; the appearances presented were suggestive of an origin from the sheath of the nerve, which of course seems hardly likely. The muscle gradually diminishes in width as it passes down towards the radius and becomes tendinous, but I did not succeed in making out the exact mode of its insertion. Dr. Gadow mentions no muscle that can be compared with this. (9) The Expansor secundariorum is present; the tendon is of considerable size ; I did not observe its mode of insertion. The Expansor secundariorum seems to be present in all the Cranes and Plovers and in most Herodiones ; its absence, however, in Cancroma and Egretta shows that it is on the wane in that group. (10) The Triceps has the usual two heads situated close together just beneath the head of the humerus. (11) The Pectoralis primus has a large insertion area on the crista superior of the humerus ; there is no second insertion such as is met with among many birds. (12) The Pectoralis secundus is well developed, and its origin extends back to nearly the end of the narrow sternum. (13) The Coraco-brachialis longus arises from the coracoid near to its articulation with the sternum and also from the sternum itself. At present there does not exist material for a detailed comparison of the musculature of the forearm and hand in different groups. The work of Dr. Gadow [16] upon Bird Anatomy contains a good general account of these muscles with their variations in a few types, while Dr. Shufeldt's essay on the Raven [20] and some few papers by other writers deal with these muscles in special forms. Although the object of the present paper is principally systematic, I give an account of the principal muscles of the forearm, since Rhinochetus is probably not an accessible type to many of those who are engaged in the study of the muscular anatomy of birds. I have not studied the intrinsic muscles of the hand in m y specimen, in the hope that on some future occasion I may have the opportunity of dissecting a recently dead specimen. When the skin is cut off from the outer side of the forearm, most of the extensor muscles are revealed without further dissection. (1) Extensor metacarpi radialis longior.-This muscle consists of two distinct parts with separate origins but a common insertion : the outer part arises by a thin tendon; this soon expands into a fusiform muscle which is decidedly smaller than the second part of the extensor; the muscle passes into a tendon at a point about half- |