720 AVES. 



part of the skeleton is invariably constructed. The framework of the 

 shoulder exhibits the scapula (fig. 355, 6), the clavicle (d), and the cora- 

 coid element (c), notwithstanding that these bones, forming, as they 

 do, the basis of a limb so vigorous, and wielded by such powerful 

 muscles, are necessarily modified in their form and general arrange- 

 ment, so as to constitute strong buttresses adapted to keep the shoulder- 

 joint firm and steady during flight. The scapula (b) is a long and 

 slender bone placed upon the ribs, and lying parallel to the spine along 

 the dorsal region of the thorax, imbedded in the muscles to which it 

 gives attachment, while at its fixed extremity it assists in forming the 

 cavity of the shoulder-joint. The coracoid bone (c) is the great support 

 of the shoulder ; for while at one extremity it sustains the wing, at 

 the opposite it is firmly and securely united to the sternum by a broad 

 articulation. But the most peculiar element of this apparatus is the 

 furculum, or forked bone (d), composed of the conjoined clavicles, 

 which, being anchylosed together in the mesial line, and also strongly 

 connected with the shoulder-joint, materially add to the stability of 

 the whole. 



(2039.) In the wing itself, the humerus (/) is at once recognized, as 

 also the ulna (g) and the radius (h). But in some birds, as in the 

 Penguin, the student might be at a loss to identify one or two small 

 bones (jp), forming a kind of patella to the elbow-joint ; these appear 

 to be the representatives of the olecranon process detached from the 

 ulna. The carpus (i) consists of only two small bones. The metacarpus 

 is formed of two pieces (k, I), anchylosed together at their two extremi- 

 ties ; and these, with two, or in some cases three rudimental fingers, 

 complete the wing. The largest finger consists of two, or sometimes 

 three phalanges (m, o) ; a second (n) offers but a single joint ; and the 

 third, which is a mere rudiment when present, is an appendage to the 

 radial side of the carpus. 



(2040.) In the pelvic extremity (fig. 354) the femur is a short and 

 strong bone ; to this succeeds the tibia, upon the outer side of which is 

 fixed a rudimental fibula. The tarsus can scarcely be said to exist, 

 being at a very early age confused with the metatarsus, the whole 

 forming a single tarso-mctatarsal bone, which, in the Wading Birds espe- 

 cially, is of very great length : at its distal extremity are three articular 

 surfaces that support the three anterior toes, while a fourth toe, the 

 Tiallux, directed backwards, is attached to it posteriorly by the interven- 

 tion of a small accessory piece ; and in Gallinaceous Birds an osseous 

 spur, consolidated with the posterior face of the tarso-metatarsal bone, 

 is generally considered as a fifth toe. 



(2041.) The number of toes varies in different tribes of birds. Thus, 

 in the Ostrich there are only two ; in many genera there are three ; in 

 by far the greater number, four ; and in the Gallinacea, five. But what- 

 ever the number of toes may be, the number of phalanges peculiar to 



