THE FOKE-LIMB 377 



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 

 ulna ; 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 carpal 



bones, proximal and distal, each row having two 

 bones. Of these the two proximal bones persist in 

 the adult, while the two of the distal row fuse with 

 the metacarpals to form the compound carpo-meta- 

 carpus. 



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 ulnare is a larger, more irregular bone, 



which articulates proximally with the ulna, 



