HORSESHOEING. 



75 



This expansion is small, and in general varies between one- 

 fiftieth and one-twelfth of an inch. 



2. A narrowing of the anterior half of the hoof measured at 

 the coronary border. 



3. A decrease in height of the hoof, with a slight sinking of the 

 heels. 



4. A flattening (sinking) of the sole, especially in its branches. 

 These changes of form are much more pronounced in the half 



of the hoof that bears the greater weight. 



A hoof while supporting the body-weight has a different form, 

 and the tissues enclosed within it a different position, than when 

 not bearing weight. Since loading and unloading of the foot are 

 continually alternating, the relations of ihternal pressure even in 

 the standing animal are continuously changing, so that, strictly 

 speaking, the hoof is never at rest. 



The changes in form take place in the following order: the 

 body-weight falls from above upon the os coronge, os pedis, and 

 navicular bone, and at the moment that the foot is placed upon 

 the ground is trans- 

 mitted through the sen- 

 sitive laminae and horny 

 laminae to the wall. At 

 the instant that the fet- 

 lock reaches its lowest 

 point the os pedis bears 

 the greatest weight. 

 Under the body-weight 

 the latter yields, and 

 with the navicular bone 

 sinks downward and 

 backward. At the same 

 time the upper posterior 

 portion of the os coro- 



nse (Fig. 73, A) passes backward and downward between the 

 lateral cartilages (a), which project above the upper border of 



Fig. 73. 



Vertical, transverse section of a foot seen from behind : 

 A, OS coronse ; B, os navicularis ; C, os pedis ; o, lateral 

 cartilage ; ft, anterior portion of fleshy frog ; c, section of 

 perforans tendon ; d, suspensory tendon of the navicular 

 bone -, I, wall ; m, sole ; », white line ; o, irog. 



