HORSE-SHOEING. 127 



resembles. At its highest point in front, the larger extensor tendon 

 of the foot is inserted, and in the middle of its lower face or sole 

 is implanted the powerful tendon which bends or flexes the foot ; 

 these tendons are the chief agents in progression. An elastic 

 apparatus surrounds them and a portion of the pedal bone, and 

 the whole is enveloped by a membrane that attaches the hoof in 

 the closest possible manner to its outer surface. Into each of the 

 wings or sides of the bone (for it is crescent-shaped, the horns 

 extending backward on eacli side) is fixed a large plate of cartilage 

 that rises above the hoof, where it may readily be felt, and which 

 has important relations with its fellow on the opposite side, as 

 well as with other elastic bodies admirably disposed to sustain 

 weight, prevent jar, and insure that lightness and springiness which 

 form so striking a feature in the horse's movements. The navicular 

 bone is a narrow piece, placed transversely between the wings of 

 the coffin bone, and is intended to throw the flexing tendon farther 

 from the centre of motion, and thus increase its power ; the tendon 

 plays over its posterior or lower face, and this disposition, together 

 with the relations established between it and the pedal bone through 

 their connecting ligaments, and the bend the tendon makes 

 in passing over it, cause this part of the foot to be one par- 

 ticularly liable to disease, and one especially deserving of atten- 

 tive study. 



The elastic apparatus of the foot consists of (1) the lateral 

 cartilages just mentioned ; (2), a prominent ring or cornice sur- 

 rounding the upper border of the pedal bone usually known as the 

 "coronary-substance," but which might be more aptly designated 

 the "coronary cushion ;" this fits into a corresponding concavity in 

 the inner and upper margin of wall of the hoof, and, besides 

 acting as an elastic body or cushion, pei'forms the important func- 

 tion of secreting this wall or crust of the horny envelop ; (3), a 

 triangular body — the plantar cushion, known to farriers as the 

 " fatty " or " sensitive frog " (to distinguish it from the horny frog. 



