652 



A MANUAL OF VETERINARY PHYSIOLOGY 



kept within £ to J inch of the ground without causing pain. 

 Growth and protection are not the only features in the foot. 

 No one can listen to the thuds of the galloping horse, or the 

 clatter of one trotting, without realising that every time the feet 

 come to the ground there must be considerable concussion unless 

 mechanisms exist for its prevention ; and no thoughtful person 

 will have any difficulty in realising that the horse's foot repre- 

 sents a remarkably small pedestal for such a bulky body to be 

 carried upon. These are the essential features comprised in the 

 physiology of the horse's foot, and must, from their paramount 



importance, be considered 

 in detail. In order to 

 elucidate them, it is de- 

 sirable to glance at some 

 of the structural features 

 of the parts concerned. 



Bones of the Foot. — The 



core of the foot consists of 

 bone, around which all the 

 other structures are moulded . 

 The bone is not one solid 

 piece, as might be imagined 

 would be necessary in such 

 a position, but, on the other 

 hand, consists of three pieces. 

 One of these is the pedal 

 bone, which is a miniature 

 foot in shape (Fig. 218), 

 while its substance is porous 

 to such an extent as to re- 

 semble pumice-stone in ap- 

 pearance and density. A 

 The dotted line through the latter indicates second bone, the navicular, 

 the portion buried within the foot, or hidden j s very small of peculiar 

 by the soft structures at the back. shape, dense 'in structure, 



rests slightly on the pedal 

 bone, and is mainly held in position by ligamentous tissue. The 

 third bone belongs partly to the foot and partly to the limb. 

 One might suppose that the pedal bone should occupy the whole of 

 the interior of the hoof, as high as the coronary edge and as far 

 back as the heels, but this is not so. It only occupies a portion of 

 the internal foot (Fig. 219), mainly situated towards the anterior 

 and lateral parts ; the posterior part of the foot contains very little 

 pedal bone, but the deficiency is made up by the introduction of 

 two large plates of cartilage attached to it, over which the structures 

 are reflected and moulded as on the bone itself. This singular 

 deficiency of bone, in a part where one might be led to regard 

 its existence as a necessity, and the presence of large carti- 

 laginous plates to take its place, is due to the lateral movements 

 the foot has to perform, and which could not be carried out if the 

 bone were proportioned relatively to the structure within which 

 it fits. The pedal bone is not placed parallel to the ground, but 



Fig. 218. — Pedal Bone and Corona 

 (Modified from Leisering). 



