22 HORSESHOEING. 



The muscles clothe the skeleton externally, give the body 

 its peculiar form, and, by their special power of contraction, 

 change the relative positions of the bones and thus make it pos- 

 sible for the animal to move. For this reason, the muscles are 

 called the active, and the bones the passive, organs of motion. 

 By carefully examining a muscle it will be found to consist of 

 actual, minute, reddish, muscular fibres. As a rule, muscles ter- 

 minate in more or less strong, glistening, fibrous cords called 

 tendons, or fibrous sheets termed aponeuroses, by which they 

 are attached to the bones. In the limbs are muscles terminating 

 in very long tendons, which act as draw-lines upon the distant 

 bones of the foot (long and short pasterns and pedal bone) and 

 set them in motion. Such long tendons are enclosed in sheaths 

 of thin, membranous tissue, known as tendon sheaths. The inner 

 surface of such a sheath is in direct contact with the surface of 

 the tendon, and secretes a thin slippery fluid (synovia) which 

 lubricates the tendon and facilitates its gliding within the sheath. 



As long as the bones, articulations, muscles, and tendons of 

 the limbs remain healthy, just so long will the legs maintain 

 their natural direction and position. Frequently, however, this 

 normal condition of the limbs is gradually altered by disease of 

 the bones, joints, and tendons, and defects in the form and 

 action of the lower parts of the hmbs arise that often require 

 attention in shoeing. 



THE FOOT. 

 A. The Bones of the Foot. 



Since the horse is useful to man only by reason of his move- 

 ments, his foot deserves the most careful attention. The horse- 

 shoer should be familiar with all its parts. Fig. 3 shows the 

 osseous framework of the foot, consisting of the lower end of the 

 cannon bone {A\ the long pastern (£), the two sesamoid bones 

 (C), the short pastern (D), and the pedal bone {E). The lower 

 end of the cannon, or large metacarpal bone {A) exhibits two 

 convex articular surfaces (condyles) separated by a median ridge 

 running from before to behind, and all covered by articular car- 



