570 DISEASES OF THE HOKSE. 



resilient horny frog, which crowds the bars apart. Of course, when 

 the lateral cartilages are ossified not only is no expansion of the 

 quarters possible, but frog pressure often leads to painful compres- 

 sion of the plantar cushion and to increase of lameness. Frog pres- 

 sure is therefore contra-indicated in lameness due to sidebones (ossi- 

 fied cartilages) . Under the descent of the coffin-bone the homy sole 

 sinks a little; that is, the arch of the sole around the point of the 

 frog, and the wings of the sole become somewhat flattened. All these 

 changes of form are most marked in sound unshod hoofs, because 

 in them ground pressure on the frog and sole is pronounced; they 

 are more marked in fore hoofs than in hind hoofs. 



The movement of the different structures within the foot and the 

 changes of form that occur at every step are indispensable to the 

 health of the hoof, so that these elastic tissues must be kept active by 

 regular exercise, with protection against drying out of the hoof. 

 Long-continued rest in the stable, drying out of the hoof, and shoeing 

 decrease or alter the physiological movements of the hoof and some- 

 times lead to foot diseases. Since these movements are complete and 

 spontaneous only in unshod feet, shoeing must be regarded as an evil, 

 albeit a necessary one, and indispensable if we wish to keep horses 

 continuously serviceable on hard, artificial roads. However, if in 

 shoeing we bear in mind the structure and functions of the hoof and 

 apply a shoe whose branches have a wide and level bearing surface, 

 so as to interfere as little as may be with the expansion and contrac- 

 tion of the quarters, in so far as this is not hindered by the nails, we 

 need not be apprehensive of trouble, provided the horse has reason- 

 able work and his hoofs proper care. 



GROWTH OF THE HOOF. 



All parts of the hoof grow downward and forward with equal 

 rapidity, the rate of growth being largely dependent upon the amount 

 of blood supplied to the pododerm, or " quick." Abundant and reg- 

 ular exercise, good grooming, moistness and suppleness of the hoof, 

 going barefoot, plenty of good food, and at proper intervals removing 

 the overgrowth of hoof and regulating the bearing surface, by increas- 

 ing the volume and improving the quality of the blood flowing into 

 the pododerm, favor the rapid growth of horn of good quality ; while 

 lack of exercise, dryness of the horn, and excessive length of the hoof 

 hinder growth. 



The average rate of growth is about one-third of an inch a month. 

 Hind hoofs grow faster than fore hoofs and unshod ones faster than 

 shod ones. The time required for the horn to grow from the coronet 

 to the ground, though influenced to a slight degree by the precited 

 conditions, varies in proportion to the distance of the coronet from the 

 groimd. At the toe, depending on its height, the horn grows down 



