Fig. 43. 



7S . THE SONES. 



surface; 6, Two diartlirodial facets elongated transversely, out on ft© 

 posterior outline of the large articular sui-face with jl'i'^^,, ^^^ ^!^,Xd 

 founded by their superior border ; they correspona 

 to similar facets on the ulna ; 7, Below these, a 

 roughened surface which extends to the radio- 

 nluM- arch, and is in contact with an analogous 

 surface of the same bone through the medium of 

 an interosseous ligament ; iii the Horse this liga- 

 ment rarely ossifies. 



The inferior extremity, flattened from before 

 to behind, presents : 1, Below, an articular sur- 

 face elongated transversely and somewhat irregu- 

 lar, responding to the four bones in the upper 

 row of the carpus; 2, On the sides, two tube- 

 rosities for ligamentous insertion, the internal 

 salient and well circumscribed, the other external 

 and excavated by a verticalfcsure, in which passes 

 a tendon ; 3, In front, *teee- grooves for the 

 gliding of tendons ; the external is the largest, and. 

 vertical like the median; the internal, the nar- 

 rowest, is oblique downwards and inwards; 4, 

 Posteriorly, a strong transverse ridge which sur- 

 mounts the articular surface and serves for the 

 insertion of ligaments. 



Structure and development. The radius is a 

 very compact bone, and is developed from three 

 centres of ossification : one for the body and two 

 for the extremities. 



2. Ulmor. 



This is an elongated, asymmetrical bone, in 

 the form of an inverted triangular pyramid, applied 

 against the posterior face of the radius, to which 

 it is united in adult solipeds. It offers for des-, 

 cription a middle portion and two extremities. 



Middle portion. — This has three faces wider 

 above than below, and three borders which become 



The 

 The 



faces for the humerus; 7, 

 Bicipital tuberosity ; 8, 

 Shaft or body of the radius ; 

 9, Grooves for tendons. 



EXTERNAL FACE OP THE 

 RADIUS AND ULNA. 



1, Ulna ; 2, Point of the ole- 

 cranon ; 3, Beak of the ok- 

 cranon:4,Eadio-ulnararch; . . j , ,, • „ . , .. <. . -i i, 



Supero-external tuberosity ; jomed at the inferior extremity of the bone. 

 6, Radio-iilnar articular sur- external face is smooth and nearly plane. 



internal is also smooth and slightly hollowed. 

 The anterior is formed to correspond to the radius, 

 and presents peculiarities analogous to those of 

 the posterior face of that bone. Tbus there is 

 found in proceeding from above to below: 1, Two small diarthrodial 

 facets ;^ 2, A rough surface ; 3, A transverse groove for the formation of 

 the radioulnar arch; 4, A triangular surface, studded with rugosities, 

 which occupies the remainder of the bone to its lower extremity. Thfe lateral 

 borders, external and internal, are sharp, and, like the anterior face, are in 

 contact with tlie radius. The posterior harder is concave, rounded, and thicker 

 than the other two. 



Extremities. — The superior extremity comprises all that portion which 

 exceeds the articular surface of the radius. It constitutes an enormous 

 ' It is represented in Man by the emaUer sigmoid notch. 



