102 



THE SKELETON OF THE HORSE 



Proximal 

 sesamoids 



First 

 plialaiix 



remarked that the bone is twisted slightly; when placed volar surface down on the table, it touches 

 the latter by three points only, the proximal tuberosities and the medial condyle. 



The Second Phalanx 

 The second phalanx (Phalanx secunda)' is situated between the first and 

 third phalanges, its direction corresponding to that of the first phalanx. It is 

 flattened from before backward, and its width is greater than its height. It may 

 be described as possessing four surfaces. 



The proximal surface presents two glenoid cavities separated by a low ridge, 



and articulates with the first phalanx. 

 The middle of the dorsal border is ele- 

 vated and roughened in front for the 

 attachment of the common extensor 

 tendon. The volar border is thick and 

 overhanging; in the fresh state its mid- 

 dle part is covered with cartilage, over 

 which the deep flexor tendon passes. 

 On either side there is an eminence, to 

 which the collateral ligament and the 

 superficial flexor tendon are attached. 



The distal surface is trochlear, 

 and articulates with the third phalanx 

 and distal sesamoid bone. It resem- 

 bles somewhat the trochlea of the first 

 phalanx, but is more extensive and en- 

 croaches more on the dorsal and volar 

 surfaces. 



The dorsal surface is convex from 

 side to side and smooth in its middle; 

 on each side of its distal part is a rough 

 depression, surmounted by a tuber- 

 osity, to both of which ligaments are 

 attached. 



The volar surface is smooth and 

 flattened. The borders which separate 

 the dorsal and volar surfaces are con- 

 cave from above downward, rounded 

 from before backward. 



Development. — The second pha- 

 lanx ossifles like the first, but the proxi- 

 mal end unites with the shaft two or 

 three months earlier. 



The Third Phalanx 



The third phalanx (Phalanx ter- 



tia)^ is entirely inclosed by the hoof, 



It presents for examination three sur- 



Tuberosity .-- #1 



Ridges for 

 attachment f- 



of middle 

 distal sesa- 

 moid ligament 



hnprint for 



tendon of 



superficial 



flexor 



Condyle -- 



Trartsverse 

 prominence 



Condyle 



Proxiinal 

 border ..^ 

 Flexor 

 surface -- 



Angle 

 Volar 

 groove 

 Volar 

 foramen 

 Semilu- 

 nar crest 

 Flexor 

 surface 



_ Seco7id 

 phalanx 



Distal 

 sesamoid 

 or navic- 

 —'ular hone 



- Third 

 phalanx 



-Digital Bones of Fore Limb of Horse; Volar 

 Aspect. 



to which it conforms in a general way. 

 faces, three borders, and two angles. 



The articular surface (Facies articularis) faces upward and backward, and is 

 chiefly adapted to the distal surface of the second phalanx, but a narrow, flattened 

 area along the volar border articulates with the distal sesamoid. The proximal or 

 coronary border bears a central eminence, the extensor process (Processus exten- 



' This bone is also called the small pastern bone or os corona. 

 2 This bone is also called the os pedis or coffin bone. 



