THE FORE-LIMB 389 



The postaxial or greater tuberosity is much 

 larger, and has on its extensor surface a deep 

 pit, the pneumatic foramen, leading to an air- 

 cavity in the shaft of the bone. 



The distal end of the humerus bears a 

 trochlear articular surface for the radius and 

 uhia ; the radial surface being preaxial, and 

 placed obliquely to the long axis of the bone ; 

 the ulnar surface being postaxial, and trans- 

 verse to the axis. 



2. The fore-arm has two bones, which are separate from 



each other along their whole length. 



i. The radius is slender and nearly straight. Its 

 proximal end, or head, presents a terminal 

 cup-shaped articular surface for the preaxial 

 condyle of the humerus ; and its distal end 

 articulates with the carpus. 



ii. The ulna is rather longer and much stouter 

 than the radius, and is slightly curved. Its 

 proximal and larger end has a large articular 

 surface for the postaxial tubercle of the 

 humerus, beyond which it projects as the 

 blunt olecranon process. Its distal end arti- 

 culates with the carpus, and with the radius. 



3. The wrist consists, in the embryo, of two rows of carpals, 



a proximal row of two and a distal row of three. Of 

 these the two proximal carpals persist in the adult, 

 while those of the distal row fuse with the meta- 

 carpals to form the compound carpo-metacarpus. 



a. The proximal row of carpals consists of two small 

 irregular bones. 



i. The radiale lies between the end of the radius 



and the manus. 

 ii. The ulnars is a larger, more irregular bone, 



which articulates proximaUy with the ulna, 



