54 THE HOESE. 



structure, as seen under the microscope, 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 papillae. The cells 

 formed on each papilla constitute a distinct horny 

 fiber, like a thick hair, and the whole are cemented 

 together 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 destruc- 

 tion of the softer intermediate substance ; but any 

 one acquainted with the structure and mode of 

 growth of true hairs will see that the fibers differ 

 from them in growing around a long free papilla 

 on the surface of the derm, instead of from a very 

 short papilla sunk deeply in a follicular involution 

 of the same. These horns are really warts, which 

 have assumed a solid and definite form, and the 

 stages by which they may have developed are illus- 

 trated in the irregularly-shaped supplementary horns 

 which are sometimes found either on the face or 

 other parts of the -body, the product of some local 

 abnormal condition of the skin.* 



* See a case of an African rhinoceros with a third horn 

 described in the Proceedings of the Zoological Society of Lon- 

 don, 1889, p. 418. 



