730 SHoEmo. 



appears still more preposterous ; for many of our cart horses 

 actually wear through a greater thickness of iron, than there is 

 horn secreted ; so that, were we to endeavour to harden their feet 

 by using them unshod, w© should have to wait until the horn of 

 their feet had become harder than iron, before our object would 

 be attained ! Again, I may ask, would shoes have been generally 

 adopted, had not experience taught horse owners the imperative 

 necessity for their employment under modern and civilised 

 requirements 1 



Young horses require to be shod, or their shoes removed, oftener 

 than older animals ; because the horn of their feet grows faster. 

 A three or four year old should generally have his shoes taken off 

 every three weeks ; though an aged horse may go a week longer. 



Growth of the Hoof. 



The hoof grows about 4 inches in the year. Usually, the yearly 

 growth at the heels is about ^ inch more than at the toes ; but 

 there are exceptions. 



Mechanism of the Horse's Foot. 



THE FOOT AS A LEVER.— I may explain to those unacquainted 

 with anatomical mechanics, that the movements of the limbs are 

 due to the action of muscles on bones. 



A muscle (which is the lean part of meat) has the power of con- 

 tracting in length on being stimulated by its nerves. Muscles are 

 attached ify bones, as a rule, by tendons, which are hard and 

 inelastic continuations of their respective muscles. 



Regard the muscle which bends the foot and aids in raising it 

 from the ground, and we shall find that it lies at the back of the 

 forearm ; that it is attached at its upper end to the bones near 

 the elbow, and at its lower end by a tendon (the flexor perforans, 

 see Fig. 6) which runs down the back of the leg, at and below 

 the knee ; passes over the back of the fetlock ; goes down the 

 back of the pastern ; and is finally attached to the base of the 

 pedal (coffin) bone. This tendon forms one of the two well-known 

 " back tendons." When the horse is standing at rest, both the 

 tendon and its muscle are " on the stretch," by reason of the back 

 of the fetlock pressing against the tendon. On the signal being 

 given from the brain, the nerves of this muscle stimulate it to 

 contract, and, on its becoming shorter, the pastern and fetlock 

 joints are bent and the heel raised. Look from a mechanical 

 point of view upon the action of this muscle, and we shall perceive 

 that we have a lever of the second order at work (Fig. 185). The 

 weight (W) is impressed downwards by the cannon bone ; the 



