OSTEOLOGY AND SYNDESMOLOGY. 33 



5. HuMERO-cuBiTAL ARTICULATION, OR THE Elbow Joint. In this, one 

 of the most perfect of the gingljmoid or hinge joints, the opposed extremi- 

 ties of the humerus, ulna, and radius mutually receive each other, and are 

 attached together by an external and internal lateral, and by an anterior 

 and posterior ligament. There is no distinct capsular ligament, although 

 the aggregate of these may be considered as such. 



The external lateral ligament {pi. 128, Jig. 8'') arises from the external 

 condyle, and is inserted into the posterior and external part of the annular 

 ligament of the radius. This ligament is confounded with the tendons of 

 certain muscles. The iiiternal lateral ligament {pi. 125, fig. 15 ') arises from 

 the inner condyle, and is inserted in a radiated manner into the inner mar- 

 gin of the great sigmoid cavity of the ulna, between the coronoid and 

 olecranon processes. It adheres to the synovial membrane, and, with the 

 other lateral ligament, strengthens the articulation. 



The anterior ligament {fig. 12 ') consists of thin fibres arising chiefly from 

 above the internal condyle and the coronoid depression on the fore part 

 of the humerus. Some are inserted into the annular ligament of the 

 radius, others into the coronoid process, while the remainder are lost on 

 the synovial membrane. The fibres of the posterior ligament extend chiefly 

 in a transverse direction from one condyle and one lateral ligament to the 

 other. 



The articulations between the radius and ulna are two in number, one 

 superior, another inferior. The shafts of the two bones are also connected 

 by the interosseous ligament {fig. 16'). In the superior articulation the 

 head of the radius is received into the lesser sigmoid cavity of the ulna, and 

 is retained in it by the following ligament. 



The annular ligament {figs. 16', 17') forms about three fourths of a 

 circle, the lesser sigmoid depression completing it. It arises from the 

 anterior, and is inserted into the posterior border of the lesser sigmoid 

 cavity of the ulna. It is lined by the synovial membrane of the joint ; 

 it encircles the head and neck of the radius in the same manner as 

 the transverse ligament of the atlas confines the odontoid process of the 

 axis. 



The oblique ligament arises from the root of the coronoid process of the 

 ulna, and is inserted into the inner side of the radius below its tubercle. 



In the inferior radio-ulnar articulation, the round head of the ulna is 

 received into the sigmoid cavity of the radius, and retained in it by a loose 

 synovial membrane or the sacciform ligament {pi. 126, fig. 1 '), which is 

 covered before and behind by some ligamentous fibres, forming an imper- 

 fect capsule, and passing from the radius to the ulna. The opposed edges 

 of the shafts of both radius and ulna are connected by a thin aponeurosis 

 called the interosseous membrane or ligament {pi. 125, fig. 16' ^). It is not 

 made very tense in any position of the limb, and serves to give attachment 

 to muscles. 



6. Kadio-carpal Articulations, or the Wrist Joint. In this joint, 

 which is of great transverse extent, the lower end of the radius and the 

 inter-articular cartilage form a socket for the scaphoid, lunar, and cuneiform 



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