236 DISEASES OF HORSES AND CATTLE. 



are soft at first, and gradually harden as they ap- 

 proach the surface. In some cases the surface 

 layer may have a mealy appearance, the outer 

 layer is constantly wearing off, and new ones 

 forming. In a well-formed foot the sole is strong 

 and arched to give strength to the wall, and also 

 to protect the sensitive sole from injuries. In 

 cases where nature has only formed a thin, weak 

 sole, or where it has been reduced in thickness by 

 the blacksmith's knife, it is then not in a condition 

 to sustain the pressure it was intended for, and as 

 a result the whole foot suffers, and the horse be- 

 comes lame. The bars at the back part of the sole 

 unite with the wall at right angles, forming a 

 strong support to the wall, and also to the sole, 

 preventing contraction of the heels. The frog is 

 the prominent, somewhat pyramidical, spongy 

 mass of horn lodged between the bars, and filling 

 up the triangular space. The frog varies in shape 

 and size, but is always well developed in a well- 

 formed foot. There are three cavities, called the 

 clefts of the frog. These clefts allow the elastic 

 or spongy elevations of the frog to expand on pres- 

 sure. It is secreted or grows from the sensitive 

 frog. The use of the frog is to lessen concussion 

 and bear a little of the weight of the body, and if 

 this frog is not large or is cut down so that it does 

 not come in contact with the ground, derange- 

 ments of the other structures soon ensue. 



Soft Structures of the Foot. — These are the lat- 

 eral cartilages, sensitive laminae, sensitive sole, 

 sensitive frog, and the coronary band or ligament. 



