44 PRINCIPLES OF VETERINARY SCIENCE 



upper extremity presents several flat facets for the corresponding 

 surface of the carpus, while the lower end has two condyles with a 

 prominent central ridge for articulation with the pastern and two 

 sesamoids. The splints are incompletely developed long bones 

 and are three sided. The upper extremity of each is enlarged and 

 articulates with the adjacent bones. The distal extremity is a 

 small nodule which can be easily felt in the living animal by run- 

 ning the hand downward along the cannon, pressing gently with 

 the fingers. 



The first phalanx, or large pastern, is a long bone situated 

 between the cannon and the small pastern in a direction obliquely 

 downward and forward. It forms an angle of 50 to 55 degrees 

 with the horizontal plane in well-formed limbs. The degree of 

 inclination varies considerably in different horses. This bone 

 presents for description a shaft and two extremities (see Fig. 

 73). The anterior surface of the shaft is convex, the posterior 

 surface is flattened and roughened. The upper end consists of 

 two shallow cavities with a deep groove between for articulation 

 with the large metacarpal bone. The distal end is less extensive 

 and articulates with the small pastern. 



The second phalanx, or small pastern, has a very short shaft, 

 and is partly enclosed by the hoof. The bone presents four 

 surfaces. The proximal surface has two shallow cavities for 

 articulation with the distal extremity of the first phalanx. The 

 distal surface is molded for articulation with the coffin and 

 navicular bones. The anterior and posterior surfaces are 

 convex and slightly roughened. 



The third phalanx, or coffin bone, is entirely concealed in the 

 hoof, to which it closely conforms in shape (see Fig. 73). It 

 presents three surfaces and two angles or wings. The articular 

 surface has two shallow cavities for articulation with the small 

 pastern, behind which is a flat area for the navicular bone. In 

 front is seen the extensor process for attachment of the tendon 

 of the extensor muscle. The anterior or wall surface slopes 

 downward and forward and corresponds to the inner surface of 

 the wall of the hoof; it has a rough, porous appearance due to its 

 large number of foramina. The inferior surface is clearly divided 

 into two parts by the semilunar crest which gives insertion to the 

 deep flexor tendon. The anterior portion is vaulted, crescent 

 shaped, and is termed "the sole surface," as it corresponds to the 



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