104 



THE BONES. 



Body. — Slightly arched and flattened before and behind, it presents for study 

 two faces and two borders. The anterior face is convex and perfectly smooth. The 

 posterior, a little concave from one extremity to the other, offers : 1. Near the 

 external border, a triangular surface, covered with asperities, elongated vertically, 

 very narrow, commencing near the upper fourth of the bone, and terminating in 

 a fine point towards the lower fourth ; this surface is brought into contact with 

 the anterior face of the ulna by an interosseous liga- 

 ^^S- 65. ment, which is completely ossilied before the animal 



-^''' reaches adult age. 2. Above, there is a wide, trans- 



verse, but shallow groove, which aids in forming the 

 radio-ulnar arch, and shows, near the point where it 

 touches the preceding surface, the nutrient foramen of 

 the bone. 3. Near the internal border, and towards the 

 inferior third, there is a vertically elongated and slightly 

 salient eminence for insertion. The two borders — external 

 and internal — are thick and rounded ; they establish an 

 insensible transition between the faces. 



Extremities. — The superior is larger than the inferior. 

 It has : 1. An articular surface elongated from one side 

 to the other, concave from before to behind, wider 

 within than without, and moulded to the articular sur- 

 face of the inferior extremity of the humerus ; there 

 is also seen, outwardly, a double depression (glenoid 

 cavities), which receives the two lips of the external 

 trochlea ; in the middle, an antero-posterior ridge, 

 which is received into the internal trochlea ; within, 

 an oval cavity corresponding to the internal border 

 of the former. 2. The external tuberosity, placed at 

 the extremity of the great diameter of the articular 

 surface ; it is prominent and well detached. 3. The 

 interned or bicipital tuberosity — a large, very rugged, and 

 depressed process, situated within and in front of the 

 glenoid cavity. 4. A little lower, and on the same side, 

 there is a strong muscular and ligamentous imprint, 

 separated from the preceding tuberosity by a transverse 

 1, Ulna; 2, point of the groove intended for the passage of a tendon. .5. The 

 coronoid process,^ a small conical eminence, at the 

 summit of which terminates, anteriorly, the median 

 ridge of the articular surface. (3. Two diathrodial 

 facets elongated transversely, cut on the posterior outline 

 of the large articular surface, with which they are con- 

 founded by their superior border ; they correspond with 

 similar facets on the ulna. 7. Below these, a roughened 

 surface which extends to the radio-ulnar arch, and is in contact with an analogous 

 surface of the same bone through the medium of an interosseous ligament. In 

 the Horse, this hgament rarely becomes ossified. 



The inferior extremity, flattened before and behind, presents : 1. Inferiorly, an 

 articular surface elongated transversely and somewhat irregular, responding to 

 the four bones in the upper row of the carpus. 2. On the sides, two tuberosities 

 * In Man this belongs to the ulna. 



EXTERNAL FACE OF THE 

 RADIUS AND ULNA. 



Ulna; 2, point of the 

 ulna; 3, beak of ulna or 

 olecranon ; 4, radio-ulnar 

 arch ; 5, supero-external 

 tuberosity; 6, radio-ulnar 

 articular surfaces for the 

 humerus; 7, bicipital tu- 

 b rosity ; 8, shaft or body 

 of the radius ; 9, grooves 

 for tendons. 



