GROWTH OF THE HOOF. 33 



their influence ; while the seasons are to some extent con- 

 cerned in the growth and shape' of the hoof. In winter 

 it widens, becomes softer, and grows but little ; in sum- 

 mer it is condensed, becomes more rigid, concave, and 

 resisting, is exposed to severer wear, and grows more 

 rapidly ; this variation is a provision of Nature to enable 

 the hoof to adapt itself to the altered conditions it has to 

 meet : hard horn to hard ground, soft horn to soft ground. 

 In this way we can account for the influence of locality 

 upon the shape of the foot. On hard, dry ground, the 

 hoof is dense, tenacious, and small, with concave sole, 

 and a little but firm frog ; in marshy regions, it is large 

 and spreading, the horn soft and easily destroyed by wear, 

 the sole thin and flat, and the frog an immense spongy 

 mass which is badly fitted to receive pressure from slightly 

 hardened soil. In a dry climate, we have an animal small, 

 compact, wiry, and vigorous, travelling on a surface 

 which demands a tenacious hoof, and not one adapted to 

 prevent sinking ; in the marshy region we have a large, 

 heavy, lymphatic creature, one of whose primary require- 

 ments is a foot designed to travel on a soft yielding sur- 

 face. Change the respective situations of these two horses, 

 and Nature immediately begins to transform them and 

 their feet. The light, excitable, vigorous horse, with its 

 small vertical hoofs and concave soles, so admirably dis- 

 posed to traverse rocky and slippery surfaces, is physically 

 incompetent to exist on low-lying swamps ; while the un- 

 wieldy animal, slow-paced and torpid, with a foot perfectly 

 adapted to such a region — its ground face being so exten- 

 sive and flat that it sinks but little, and the frog developed 

 to such a degree as to resemble a ploughshare in form, 

 which gives it a grip of the soft, slippery ground — is but 

 indifferently suited for travelling on a hard, rugged sur- 

 face. In process of time, however, the small concave 

 hoof expands and flattens, and the large flat one gradu- 



