FIRST INTERPHALANGIAL ARTICULATION OR CORONET-JOINT 273 



In addition to a capsular ligament, common to all the bones, there are 

 also two lateral ligaments uniting the canon with the large pastern, and 

 two lateral sesamoid ligaments, each having two branches extending from 

 the bones of that name forward, one to the lower and outer part of the 

 large metacarpal bone, and the other to the upper and outer part of the 

 long pastern bone (fig. 357). 



As the sesamoid bones have no support from below, it is necessary 

 they should have it from above, to prevent their undue descent. This is 

 provided by the suspensory ligament (fig. 356), the lower extremity of 

 which, after dividing into two thick strands, is inserted into these bones. 

 A similar provision is made to prevent too great upward displacement. 

 For this purpose three ligaments {inferior sesamoid), distinguished respec- 

 tively as the long, short, and crucial, connect the sesamoid bones with the 

 posterior border of the os coronse, and with the posterior surface of the 

 long pastern. 



The movements of this joint are hiuge-like and of great range both in 

 flexion and extension. 



FIRST INTERPHALANGIAL ARTICULATION OR 

 CORONET-JOINT 



This is a simple joint, of limited action, and formed by the union of the 

 lower extremity of the os suffraginis with the upper extremity of the small 

 pastern. The ligaments which unite these bones together are a capsular 

 ligament, two strong short lateral ligaments, some of the fibres of which 

 descend and ultimately become connected with the extremities of the 

 navicular bone, and two short posterior ligaments (fig. 357). 



Its movements are those of flexion and extension. 



SECOND INTERPHALANGIAL ARTICULATION OR 

 COFFIN-JOINT 



The bones concerned in the construction of this joint are tlie os coronae 

 or coronet-bone, the os pedis or foot-bone, and the os naviculare or navi- 

 cular bone. The two last-named bones are united together in such a 

 manner as to form two concavities separated by a slight central ridge, to 

 which are applied the two convexities and central groove upon the lower 

 end of the coronet-bone. 



The ligaments of this joint are: 1, The capsular, common to the three 

 bones. 2. The lateral ligaments uniting the os coronas to the foot-bone. 

 3. The navicular ligaments: a, the broad or interosseous ligament extending 



VOL. II. 52 



