THE LIMBS. 187 



The last segment or "joint" of the human finger 

 (see Fig. 24, p. 190) differs as much from that of the 

 horse in the use to which it is applied as is possible, 

 yet an examination of its structure will afford a good 

 key by which to understand the more complex ar- 

 rangements of the latter. It contains one bone the 

 terminal or ungual phalanx. The proximal or up- 

 per end of this is wide transversely and hollowed 

 out, fitting by a hinge- joint to the convex surface of 

 the distal end of the second or middle phalanx of the 

 digit. The two bones are firmly bound together by 

 strong ligaments placed on each side of the joint, al- 

 lowing free movement of flexion and extension, "but 

 not in any other direction. Below the joint the bone 

 is somewhat constricted, but broadens out again into 

 a sort of spoon-shaped end. The upper or dorsal 

 surface is convex, the under or palmar surface flat. 

 The ends of two tendons, which are worked by mus- 

 cles situated a long way up in the limb, are fixed, one 

 on the upper and the other on the under surface of 

 the bone, and by their alternating contractions and 

 relaxations cause it, with the structures around, to 

 move in either direction on its hinge-like articulation. 

 Between the bone and the skin are various soft struc- 

 tures, the terminations of arteries, veins, lymphatics, 

 and nerves, embedded in a web of cellular or areolar 

 fibrous tissue, with a considerable amount of fat, of 



