146 TEE ARTICULATIONS. 



superior articular face of tlie humerus and, widening as it descends, reaches 

 the radius. Its median fibres, which are the longest, are directed vertically 

 downwards to reach the imprints situated below the bicipital tuberosity ; 

 its anterior fibres, curved forwards, are united to the tendon of the coraoo- 

 radial muscle, or are confounded with the anterior ligament ; the posterior 

 are turned backwards, near their inferior extremities, to join the arciform 

 fibrous fasciculi which inwardly unite the ulna to the radius. The middle 

 fibres of this ligament cover the inferior insertion of the short flexor of the 

 fore-arm and, in part only, that of the long flexor. It is covered by the 

 ulna-plantar nerve and the posterior radial artery and vein. 



c. The anterior or capsular ligament (Fig. 85, 9) is a membraniform band, 

 attached by its superior border above the humeral articular surface, and by 

 its inferior to the anterior margin of the radial surface. By its lateral 

 borders, it is confounded with the funicular ligaments. Its internal half 

 is formed of vertical fibres which descend from the humerus and expand 

 over the radius, where they become united with the inferior tendon of the 

 coraco-radial muscle. In its external moiety it is extremely thin, and 

 composed of fibres crossed in various directions. Lined internally by 

 synovial membrane, this ligament is in contact, by its external surface, with 

 the anterior radial vessels and nerves, the two flexor muscles of the fore-arm, 

 the anterior extensor of the metacarpus, and anterior extensor of the 

 phalanges. The two latter muscles are even attached to it in a very evident 

 manner. The elbow articulation, closed in front and on the sides by the 

 three ligaments just described, has no particular ligaments posteriorly ; but 

 it is powerfully consolidated there by the olecranian insertion of the extensor 

 muscles of the fore-arm, and by the tendons of origin of the five flexor 

 muscles of the metacarpus or phalanges. 



Synovial membrane. — This membrane is very extensive and, stretched 

 out on the internal face of the before-mentioned ligaments, forms behind 

 three great culs-de-sac of prolongment : a superior, occupying the olecranian 

 fossa, and covered by a fatty cushion, as well as by the small extensor 

 muscle of the fore-arm ; ^ two lateral, which descend from each side of the 

 ulnar beak, and are distinguished as internal and external ; the first lir 

 the tendon of the external flexor of the metacarpus ; the second facilitates 

 the play on the upper radial extremity of the four flexor muscles of the foot 

 or digits, and which are attached in common to the epitrochlea. This synovial 

 sac also furnishes the radio-ulnar articulation with a diverticulum which 

 descends between the bones of the fore-arm to below the adjacent diar- 

 throdial facets. 



Movements. — Flexion and extension. 



Inflexion, the two bones do not approach each other directly, the inferior 

 extremity of the radius deviating a little outwards. This is due more to 

 the slight obliquity of the articular grooves than to the difference in 

 thickness existing between the external and internal extremities of the 

 humeral surface. 



Extension is limited by the reception of the beak of the olecranon in its 

 fossa, and by the tension of the lateral ligaments ; so that the two rays 

 cannot be straightened on one another in a complete manner, or placed on 

 the same line. 



In the Dog and Cat, the external lateral ligament is very thick, and forms in its 



' Some grey elastic fibres wliich cover this cul-de-sac externally, have been wronslv 

 described as a posterior membraniform ligament. 



