142 ARTHRCLOGY, 



or intersesamoidean ligament, and covered by a pad of fibro- 

 cartilage, which forms a smooth groove for the passage of the 

 flexor tendons, and is converted into a canal by the annular 

 ligament, a strong fibrous band which forms an arch posteriorly 

 from one sesamoid bone to the other. The joint is capable of 

 flexion and extension, with very slight lateral motion. 



The synovial membrane of this joint is continued upwards 

 posteriorly, in the bifurcation of the suspensory ligament, where 

 it forms a large cul-de-sac. "Wind-galls" are projections of 

 this sac when it is abnormally full. 



PASTERN JOINT. 



The Proximal interphalangeal articulation, or pastern joint, 

 is formed by the proximal and mesian phalanges, joined by the 

 capsular, lateral, and two posterior ligaments. The capsular 

 ligament extends from the articular margin of one bone to that 

 of the other, and is adherent in front to the extensor tendon. 

 The lateral ligaments are large and very strong, springing from 

 the distal end of the os suffiraginis and passing obliquely 

 downwards to the postero-lateral aspect of the os coronss. 

 The two posterior ligaments run each from three points 

 on the sides of the os suffraginis to a piece of fibro-cartilage, 

 described as the glenoid cartilage, and attached to the postero- 

 superior edge of the os coronae ; between them is the insertion 

 of the external inferior sesamoidean or Y-shaped ligament. 



The synovial membrane of this joint lines the glenoid cartilage 

 and a portion of the extensor tendon, and sends upwards a sac 

 v/hicK lies between the postero-inferior part of the first phalanx 

 and the cartilage. The movements are flexion and extension, 

 and, during flexion, some slight lateral motion. 



COFFIN JOINT. 



The Distal interphalangeal articulation, or coffin joint, is 

 formed by the mesian and distal phalanges and the navicular 

 bone. Its ligaments are the capsular, antero and postero- 

 lateral, and the broad, lateral, and inferior navicular. The 

 capsular ligament includes the articulation formed by the three 

 bones, and is attached to the extensor tendon in front and the 

 flexor behind. The antero-lateral, which are strong and thick,. 



