90 



THE SKELETON OF THE HORSE 



middle ; on its lower part are lateral rough depressions, surmounted by tuberosities, 

 to both of which ligaments are attached. 



The posterior or volar surface is smooth, flattened, and slopes obliquely down- 

 ward and forward. The i)orders which separate the anterior and posterior surfaces 

 are concave from above downward, rounded from before Ijackward. 



Development. — The second phalanx ossifies like the first, but the proximal 

 end unites with the shaft two or three months earlier. 



Third Phalanx 



Third Sesamoid 



Second Phalanx 



First Phalanx 



~ Distal border 



- Dorsal or wall surface 

 Extensor process 



^,.' Articular surface 

 Coronary border 

 Dorsal groove 

 Depression for lateral ligament 



— Angle or %nng 



Articular surface of third sesamoid or 

 ■navicular bone 



-- Distal articular surface 



Eminence for latercd ligament 

 Dorsal surface 



Proximal articular surface 



Distal articular surface 

 Eminence for lateral ligament 



Dorsal surface 



— - Eminence for extensor tendons 



— Tuberosity 



— Proximal articular surface 

 ' Intermediate groove 



Fig. 58. — Phalanges and Third Sksamoid of Horsk, Dorsal Aspect. 



The Third Phalanx 



The third or ungual phalanx (Phalanx tertia)' is entirely inclosed by the hoof, 

 to which it conforms in a general way. It presents for examination three surfaces, 

 three borders, and two angles or wings. 



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

 chiefly adaptcnl to the distal surface of the second ]ihalanx, but a narrow flattened 

 area along the posterior border articulates with the third sesamoid. The an- 



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



