The Foot — Its Description. 105 



surface of the tendo-'perforans^ become united at 

 their inner sides with the superior margin of the 

 sensitive frog, are covered inferiorly by the sensi- 

 tive sole, and at the same time assist in the 

 support of the sensitive frog. They are trian- 

 gular in form and are arched in the same manner 

 as the sole. Their use appears to be to fill up 

 the triangular vacant spaces left between the 

 tendo-perforans and the heels of the coffin-bone, 

 thereby completing the surface of support for the 

 frog, and extending that for the expansion of the 

 sole. The navicular bone is a small bone resem- 

 bling a weaver's shuttle and has a side-to-side 

 movement after the manner of such implement ; 

 hence it is sometimes called the shuttle-bone. 

 One of the chief uses of this bone appears to 

 be to take off a portion of the weight from the 

 coffin-bone, and from the navicular bone it is 

 thrown on the tendon which rests on the frog 

 beneath. It is on the inner surface of this bone 

 that the navicular disease first originates ; infiam- 

 mation is set up by severe concussion, and, being 

 deep-seated, quite out of the reach of medical 

 and surgical treatment, the inflammation becomes 

 chronic, the membrane covering the joint is 

 affected, small tumours form on the navicular 

 bone, much after the nature of splint ; the navi- 

 cular bone becomes porous, resembling a piece of 

 pumice stone, and the animal is lame for life. 

 / Much of this disease is caused by bad shoeing; 

 /; cutting and carving the frog and sole have done 

 jv more to ruin the horse than all the grooms in 

 Christendom. 



