68 THE SURGICAL ANATOMY OF THE HORSE 



The inferior surface is also articular, and on it are two convexities 

 separated from one another by a shallow antero-posterior groove. 

 This surface articulates with the superior surface of the second 

 phalanx. 



The first phalanx ossifies from three centres — one for the shaft, and 

 one for each extremity — and it possesses a medullary cavity. 



THE SECOND PHALANX 



This bone is also termed the os corons, and frequently also the short 

 pastern bone. It runs obliquely downwards and forwards between the 

 pastern and corono-pedal joints. It does not possess a medullary cavity, 

 and belongs to the class of short bones. 



It possesses six surfaces. The superior surface is articular, and is 

 moulded on to the inferior articular surface of the first phalanx. Its 

 inferior surface is also articular, and presents a shallow antero-posterior 

 groove separating two slight convexities. This articular surface en- 

 croaches upon the anterior aspect of the bone, and to this encroaching 

 area the upper or anterior surface of the navicular bone is articulated. 

 To the remainder of the inferior surface the pedal bone, or third phalanx, 

 is articulated. 



The remaining surfaces are non-articular. The anterior surface is 

 most extensive in its transverse dimension, and it presents a slight depres- 

 sion. The posterior surface is perforated by a number of small foramina 

 for the passage of blood-vessels into the bone. Near its upper extremity 

 this surface presents a transversely elongated, smooth area, to which the 

 complementary cartilage is attached. 



The lateral surfaces are roughened. Inferiorly each presents a shallow 

 pit. To these surfaces the lateral ligaments of the pastern and corono- 

 pedal joints are attached. 



The second phalanx ossifies from three centres. 



