50 



THE HOKSE 



massive indurated, almost inflexible, plates, with thin 

 soft intervals or joints, to allow of motion. Hairy 

 covering scanty. Tail of moderate length, slightly 

 tufted. Limbs stout, rather short. Three completely 

 developed toes, with distinct, broad, rounded hoofs on 

 each foot. 1 



All existing species have one or two horns, placed 

 in the middle line upon the face. When one is present, 

 it is situated over the conjoined nasal bones ; when two, 

 the hinder one is over the frontals. These horns differ in 

 details of structure from those of any other animal, though 

 belonging to the same category of epidermic growths as 

 the horns of oxen, as well as nails, claws, hoofs, callosities 

 and warts. Their structure, as seen under the micro- 

 scope, has a great resemblance to that of whalebone, being 

 composed of a solid mass of hardened epidermic cells 

 growing from a cluster of long dermal papilla. The 

 cells formed on each papilla constitute a distinct horny 

 fibre, like a thick hair, and the whole are cemented to- 

 gether by an intermediate mass of cells which grow up 

 from the interspaces between the papillae. It results 

 from this that the horn has the appearance of a mass of 

 agglutinated hairs, which, in the newly-growing part at 

 the base, readily fray out on destruction of the softer 

 intermediate substance ; but any one acquainted with 

 the structure and mode of growth of true hairs will see 



1 In some extinct species a small outer toe is present on the 

 fore-foot. 



