86 HORSESHOEING. 



Also tlie relative length of side-walls, or of toe and heels, 

 influences rapidity of wear of the shoe. If through ignorance 

 or carelessness one side-wall be left too long, the branch beneath 

 will meet the ground before other parts of the shoe and will 

 wear faster (see Eigs. 87, 88 and 89). 



The wear of the hoof upon the shoe occurs as a result of the 

 movements of the quarters. Visible indications of this are the 

 brightly polished, often sunken places upon the bearing-surface 

 of the ends of the branches, showing that scouring occurs be- 

 tween the horn and the iron. Shoes which show brightly pol- 

 ished places in their anterior halves have been loose. The wear 

 of the quarters upon the shoe is not always uniform, but is 

 usually greater on the inner than on the outer quarter, especially 

 in base-wide feet. The degree of this wear of the hoof may be 

 from nothing to one-fourth of an inch or more from one shoeing 

 to the next. Finally, we should remember that this usually 

 invisible scouring away of the hoof gradually causes the nails 

 at the quarters to become loose, and that this is more clearly 

 marked in the front than in the hind hoofs. 



G. Physiological Movements of the Hoof. (Mechanism of the 

 Hoof.) 



These movements comprise all those changes of position 

 within and of the hoof which are brought about by alternately 

 weighting and relieving the foot, and which are manifest as 

 changes of form of the hoof. The following changes in form of 

 the hoof are most marked at the time that the hoof bears great- 

 est weight, — that is, simultaneous with the greatest descent of 

 the fetlock- joint. 



1. A lateral expansion over the entire region of the quarters, 

 occurring simultaneously at the coronary and plantar borders. 

 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. 



