OR OSSEOUS SYSTEM, 



101 



FIG. 55. 



the frontal bones in the males of most genera of this order, 

 extend upwards into permanent processes, of a loose can- 

 cellated structure, which are covered with permanent, horny, 

 and extravascular sheaths, as in antelopes, sheep, goats and 

 oxen. In the deers the antlers are deciduous, organized 

 osseous processes, continued from the same tuberosities of 

 the frontal bones, with thick, dense, and very compact pa- 

 rieties, and a softer internal core passing through all the 

 branches. These deciduous horns, which are diverticula of 

 the blood at stated seasons, and intimately connected in 

 their development with the condition of the genital system, 

 are annually cast and renewed, each successive pair being 

 larger and more complex in form than the preceding. There 

 are permanent rudimentary osseous horns in the giraffe, 

 together with a median frontal eminence, like that on the 

 frontal bone of the two-horned rhinoceros ; but there are 

 no horns in the camels, dromedaries, lamas, pacas, and 



