46 ANATOMY OF THE DOMESTIC FOWL 



The Ulna. Location. The ulna, larger than the radius, is bent 

 and articulates with the radius only at the ends. The two bones 

 are bound together by a ligamentous band. It also articulates 

 superiorly with the distal end of the humerus, and inferiorly with 

 the carpus. When the wing is folded the radius is superior and a 

 trifle to the inner side of the ulna. 



Description. The proximal end is most expanded, and is obliquely 

 truncate for the articular excavation adapted to the ulnar tubercle 

 of the humerus. A short angular process behind the cavity repre- 

 sents the elecranon, which is the processus olecranalis coracoideus 

 ulna to which the ligamentum capsulare cubiti attaches. On the 

 inner side of the head is the internal tubercle of the ulna and on the 

 external side the external tubercle of the ulna. An excavation is 

 noted on the radial side of the proximal end for the lateral articula- 

 tion of the head of the radius. On the upper side near the articular 

 part is located the sigmoid cavity. 



The shaft, or corpus ulnae, decreases in size near the distal end. 

 It is slightly curved, flattened laterally with an internal and an ex- 

 ternal ridge. 



The distal end of the ulna is slightly expanded into a trochlea 

 which is sharply convex and articulates with two free carpal bones, 

 the scapho-lunar, or os carpi radiale, and the cuneiform, or os carpi 

 ulnare. The scapho-lunar is placed on the radial side, and the carpi- 

 ulnare on the ulnar side. The distal extremity of the ulna is pro- 

 vided with a styloid process and on the dorsal side with a tubercle. 



The Radius. Location. The radius lies beside the ulna with 

 which it articulates at each extremity. At the inferior extremity the 

 articulation is rotary. It also articulates superiorly with the hu- 

 merus and inferiorly with the os carpi radiale. 



Description. The radius, cylindrical in shape, is more slender 

 than the ulna. 



The proximal end is expanded, subelliptical, with a concavity 

 for the oblique tubercle and a thickened convex border for articu- 

 lation with the ulna. This end is provided with the tuberositas 

 radii. 



The shaft, or corpus radii, is slender, subcompressed, and has a 

 slight bend upward from the ulna. A nutrient foramen occurs in 

 this shaft. 



The distal end is expanded and rather flattened with two grooves 

 on the anconal side for passage of tendons. For articulation with 



