PIGEON. 3S 



RADIUS AND ULNA. 



The former bone is always the more slender of the two. The 

 Tipper end of the radius shews a cup-shaped depression, for articu- 

 lation with the inner articular surface of the lower end of 

 humerus. This end has also a convex border next the ulna, for 

 articulation with that bone. The ulna is slightly curved, and the 

 proximal end is most expanded, having an articular excavation for 

 the outer convex surface in lower end of humerus. The distal 

 end of the ulna is slightly -expanded into a trochlear joint, which 

 articulates with the two free carpel bones — one, the scapho-lunar, 

 wedged into the radial part ; the other, cuneiform, into the ulnar 

 part, leaving an intermediate space for the os magnum, which is 

 confluent with the middle metacarpel. 



The two most external of the normal five meta,carpels are not 

 represented, but the remaining three are anchylosed together 

 with the os magnum, into a single bone. This bone appears as if 

 it were composed of two metacarpels, united at their extremities,, 

 but free in the middle. 



The outer metacarpel, that which corresponds to the radius, is 

 the longer portion, and is, as its development shews, composed of 

 two; it carries the digit which has the greatest number of 

 phlanges. This digit answers to the index finger, and consists of 

 three phlanges ; the digit attached to the ulnar metacarpel con- 

 sists of only a single short phalanx. 



OS INNOMINATUM 



Is composed of three bones — ilium, ischium, and pubis — all of 

 which are indistinguishably anchylosed. In the young pigeon,/ 

 these bones were distinct. It is remarkable for the great elonga- 

 tion, both anteriorly and posteriorly, of the iliac bones, which 

 unite with the entire length of the sides of the sacrum. There 

 is an articular surface on the ilium, upon which the great tro- 

 chanter of the femur plays, called the antitrochanter. The 

 ischium broadens posteriorly, extending back nearly parallel to 

 the hinder part of the ilium, being united with it by ossification 

 behind. The pubis, after entering into the formation of the 

 acetabulum, passes downwards and backwards as a slender 

 curved bone, nearly parallel with the ischium. It is united with 

 its fellow only by fibrous tissue, there being no symphysis pubis. 



FEMUR 



Is a short bone with a small head, which fits into' the acetabular 

 cavity of the innominate bone. The head is sessible on the shaft — 

 that is, it has no neck. 



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