286 



AVES. 



the humerus presents a notable process at the 

 outer side, near its lower extremity; and in 

 the Puffin C Fralercula arctictt) an ossiculum 

 is moveably articulated to this process. 



Another ossiculum may here be noticed, al- 

 though it belongs rather to the ulna, being 

 essentially the separated olecranon of that bone. 

 This detached sesamoid bone is found attached 

 (like the patella of the knee-joint) to the capsular 

 ligament and the tendons of the extensor mus- 

 cles, in many of the Raptores, and in the Swifts. 

 In the Penguins it is double (n, n, fig. 130.) 



Of the two bones of the antibrachium 

 (y, fig. 125) the ulnar (o, fig. 130) is always 

 the strongest, and especially so in the Stru- 

 t/nones: both this and the radius (p,fg. 130) 

 are in general slender and straight bones, 

 slightly enlarged at their extremities, placed 

 not by the side of, but one in front of the other, 

 and so articulated together, and with the hu- 

 merus, as to admit of scarcely any degree of 

 pronation or supination, which, as Meckel 

 justly remarks, adds to that firmness and resist- 

 ing power in the anterior member which are 

 so necessary during the actions of flight. In 

 the Penguins, the bones of the fore-arm present 

 the same modifications as the humerus in re- 

 lation to the corresponding action in the denser 

 element, or that of swimming : they are flat- 

 tened, and are articulated with the anterior 

 edge, and not the extremity of the humerus. 



The bones of the hand are extended in 

 length, but restricted in lateral development. 

 The carpus consists of two bones only, (q, fig. 

 1 30,) so wedged in between the antibrachium 

 and metacarpus, as to limit the motions of the 

 hand to those of abduction and adduction 

 necessary for the folding up and expansion of 

 the wing ; the hand is thus fixed in a state of 



Fig. 131. 



Pelvis and bones of the ley of the Diver, or Loon, Colymbus glacialis. 



pronation ; all power of flexion, extension, or of 

 rotation, is removed from the wrist-joint, so that 

 the wing strikes firmly, and with the full force of 

 the contraction of the depressor muscles, upon 

 the resisting air. 



The metacarpus is principally formed of two 

 bones, anchylosed together at both extremities 

 (r, r, Jig. 130); of these, the one which cor- 

 responds to the radius is always the largest, 

 and supports the finger which has the greatest 

 number of phalanges : a third small rudi- 

 mental bone is in most birds found an- 

 chylosed to the outer-side of its proximal 

 extremity, and this supports the single phalanx 

 of what is usually called the thumb. The 

 longest or radial finger is generally composed 

 of two phalanges (s, a, fig- 130) of moderate 

 length ; to which, in some birds, a third smaller 

 phalanx is added. The ulnar finger consists of 

 a single phalanx only (t,jig. 130). These are 

 strongly bound together by ligaments and in- 

 tegument, so that the wing loses nothing of its 

 force, while it preserves in these separated 

 bones its analogy with the anterior extremities 

 in the other vertebrated classes. In Zoology 

 the large feathers that are attached to the ulnar 

 side of the hand, are termed Primaries or pri- 

 mary feathers ; those which are attached to the 

 fore-arm Secundariee, or secundaries, and Tec- 

 trices, or wing-coverts ; those which lie over 

 the humerus are called Scapularue, or scapu- 

 laries ; and those which are attached to the 

 thumb, Spuriee, or bastard feathers. In some 

 birds the wing is armed with a spur attached 

 to a phalanx at the radial side of the so-called 

 thumb, which, as Nitzsch observes, would 

 therefore seem analogous to the index finger. 



The bones of the leg or posterior extremity 

 (Jig. 131J do not exactly correspond, in their 

 divisions or principal 

 groups, to those of the 

 wing, the segment corre- 

 sponding to the carpus 

 being invariably blended 

 with the one that suc- 

 ceeds. 



The pelvic bones present 

 a remarkable contrast to 

 those of the shoulder, 

 being always anchylosed 

 on either side into one 

 piece, but being with 

 one exception | never 

 joined in the mesial line, 

 while this is theonlyplace 

 where the elements of the 

 scapular apparatus are in 

 general united by bone. 

 In the young bird the 

 os innominatum is seen 

 to be formed by the usual 

 three bones, viz. the ilium, 

 ischium, and pitbis, corre- 

 sponding respectively to 

 the scapula, coracoid, and 

 clavicle, of the anterior 

 extremity. 



The ilium ($,fg. 125, 

 n, fig. 131.) is the only 



