io6 THE HORSE 



of as the " insensitive frog/' in contradistinction to the 

 " sensitive frog," upon which the former is moulded, 

 and secreted by the papillae on the lower surface of the 

 latter. The horny frog has a central depression or 

 middle cleft, and on either side a lateral cleft, plainly 

 visible on the lower surface. The inner surface of the 

 frog is, as previously stated, moulded upon the sensitive 

 frog, and there is a backward projection or plate of horn 

 called the frog-stay. Normally, the frog is a well- 

 developed elastic pad and a very effective anti-slipping 

 agent, therefore it shows how very important it is for the 

 farrier to leave it intact as much as possible, and to shoe 

 the animal in such a manner that the functions of the 

 frog may not in any way be interfered with. Contrac- 

 tion of the heels immediately follows the removal of 

 frog pressure, which readily takes place when the heels 

 are raised, hence the advisability whenever practicable 

 of shoeing a horse perfectly fiat. 



Situated on either side of the frog are the " bars,'* 

 which represent reflexions of the wall at the heels. The 

 bars give additional strength to the frog, and to sonie 

 extent are weight-bearing structures. Like the frog, 

 they should not be interfered with, although we have 

 seen — ^fortunately, not often — the farrier slicing them 

 away, and so paving the way for the future ruin of the 

 foot. The horn of the wall, likewise that of the sole and 

 the frog, is continually being renewed, therefore there is 

 a gradual shedding of the most superficial layer. This 

 is particularly well seen in the unshod foot on the sole, 

 in which ex-foliated portions of the horn sometimes 

 accumulate, which should be removed with a knife. 



All the soft structures are enclosed within the hoof, 

 and the foot has a very rich blood supply. In order to 

 facilitate a free circulation of blood the veins of the foot, 

 unlike those of the body, are without valves, in addition 

 to which the vessels form a complex network. This 

 distribution of the blood-vessels is largely in connection 



