74 HORSESHOEING. 



which are fretful and prance under the rider, draw heavy loads, 

 or from any other cause, as disease or infirmity, are obliged to 

 shorten their steps. With increase of length of stride the wear 

 of the shoe becomes more uniform. 



Also the position and form of the shoe have a marked influence 

 upon its wear ; at the place where the shoe is too far under 

 the hoof, either as a result of shifting or of having been nailed 

 on crooked, or where the outer branch has not the necessary 

 width, or does not form a sufficiently large curve, the wear will 

 be increased. 



Ihe 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-fifth of an inch or more from one shoeing to 

 the next. Finally, we should remember that this usually invisi- 

 ble 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. 



F. 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 greatest 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. 



