HORNS OP MAMMALIA. 



101 



instead of forming a right angle with the vertebral column, 

 become parallel with the axis of the body. The mode in which 

 the lower jaw is articulated with the cranium, is characteristic of 

 the Mammalia ; this bone is directly connected with the skull, by 

 two projecting condyles ; and the portion of the temporal bone 

 which receives it, is united with that which forms part of the 

 walls of the skull ; whilst amongst Birds, Reptiles, and Fishes, 

 the jaw is suspended by an intermediate bone, interposed 

 between it and the main portion of the temporal. 



82. Some of the Mammalia have a remarkable peculiarity in 

 the conformation of their head, the existence of horns of various 

 lengths. Sometimes these prolongations are only appendages of 

 the skin, and appear to be formed of hairs united together ; this 



is the case with the tusk with 

 which the nose of the Rhinoceros 

 is armed. In general, however, 

 it is otherwise; the axis, or centre 

 of these appendages being formed 

 by a prolongation of the frontal 

 bone. The Mammalia which are 

 furnished with bony, branching 

 horns, all belong to the order of the Ruminants ; and exhibit very 



considerable differ- 

 ences in the structure 

 of these organs. The 

 bony protuberance 

 is sometimes covered 

 by the skin of the 

 forehead, which does 

 not differ at this part 

 from that of the rest 

 of the body, and 

 which does not 

 change ; this is the 

 case with the Giraffe. 

 In other cases, the 

 covered with a hairy 



FIG. 53. RHINOCEROS. 



FIG. 54. STAG. 



bony portion of these horns is at first 



