84 THE BONES'. 



SESAMOIDS. These are two small short bones placed side by side behind 

 the superior extremity of the first phalanx, whose articular surface it 

 completes, as it has not extent enough to be exactly adapted to the 

 metacarpal surface. Each of these -bones represents a small, irregularly- 

 shaped polyhedron, or rather, a short trifacial pyramid. It offers : an 

 anterior face, which is articular, and corresponding to the inferior extremity 

 of the principal metacarpal bone, moulded, as it were, on one of the condyles 

 and one of the sides of the median ridge ; a posterior face, covered with 

 cartilage in the fresh state, and forming, with that of the opposite bone, 

 a gliding concave surface for the flexor tendons of the phalanges ; a lateral 

 face, studded with ligamentous imprints ; a summit, directed upwards ; and a 

 base, turned downwards, and serving for the attachment of several ligaments. 

 SECOND (OR MIDDLE) PHALANX (Os CORONJS, SMALL PASTERN BONE). 

 This is a short bone, situated in the same oblique direction as the first 

 phalanx, and between it and the third. Its general form is that of a cube 

 flattened before and behind, and offering the following features : an anterior 

 face, covered with some slight imprints ; a posterior face, provided, above, 

 with a transversely elongated gliding surface ; a superior face, channeled 

 by two glenoid cavities, to match the inferior articulating surface of the 

 first phalanx ; an inferior face, formed on the same plan as the last, being 

 occupied by two unequal condyles which articulate with the third phalanx 

 and the navicular bone ; two lateral faces exhibiting a very marked imprint. 

 In the interior of this bone is found a nucleus of very condensed spongy 

 substance, enveloped in a layer of compact tissue. It is usually developed 

 from a single centre of ossification ; though in many subjects there is a 

 complementary nucleus for the superior articular surface and the posterior 

 gliding surface. 



THIRD (DISTAL) PHALANX, Os PEDIS (OR PEDAL BONE). This is a short 

 bone which terminates the digit, and sustains the hoof' that incloses it and 

 the navicular bone. When completed by a special fibro-cartilaginous apparatus, 

 it represents the segment of a very short cone, obliquely truncated behind, 

 from the summit to the base. It offers for study: three faces, three borders, 

 and two lateral angles 



Faces. The anterior, convex from side to side, and cribbled by porosities 

 and vascular openings, shows on each side : 1, 

 The preplantar fissure, a horizontal groove more 

 or 1 less ramified, which commences behind, 

 between the retrossal and basilar processes, ter- 

 minating in front in one of the foramina which 

 penetrate the bone ; 2, The patilobe eminence, a 

 roughened projecting surface, situated between the 

 preceding fissure and the inferior border of the 

 bone. The superior face is occupied by an articu- 

 lar surface formed by two glenoid cavities and a 

 slight median ridge ; it comes in apposition with 

 PLANTAR SURFACE OF THIRD tne inferior face of the second phalanx. The 

 PHALANX. inferior (or soZar) face, hollowed out like an arch, 



1, Lower face, or sole ; 2, 3, is divided into two regions by the semilunar crest, 

 Wings, or retrossal pro- a Ra li e ,nt line which describes a curve forwards, 

 cesses; 4, Internal border; The anterior region ig per f ora ted with very fine 

 o, xiantar loramina. . . _ <-* * . - i / /i 



porosities, and corresponds to that part of the 



hoof named the sole. The posterior region shows, immediately behind the 

 semilunar crest, a median imprint, and two lateral channels designated the 



