MAMMALS 79 



work on the Antelope and Deer of America} This author 

 states that the blood-vessels of the antler are derived from 

 three sources : (1) the arteries of the periosteum, which, as 

 in the long bones of the skeleton, pass into the bone trans- 

 versely to its surface ; (2) arteries from the periosteum of 

 the pedicle, which turn in at the top of the pedicle, and 

 thence pass u through the interior of the new antler; 

 (3) arteries which pass up through the interior of the 

 pedicle into the growing antler. He states that, as 

 ossification proceeds, the tips of the antlers first become 

 solidified quite through, and the solidifying process extends 

 downwards, so that the apertures which admitted the arteries 

 from the periosteum become closed. This, however, does not 

 destroy the periosteum or velvet, because the former is still pro- 

 vided with a venous as well as an arterial system, running in 

 its own substance. Some authorities have maintained that the 

 death of the velvet was due to the fact that the deposit of bone 

 which forms the " burr " at the base of the antler constricts 

 the arteries which enter the velvet, and so cuts off its supply 

 of blood. But Caton asserts from his own observation that 

 the velvet is rubbed off purposely by the animal against small 

 trees, etc., and that it is at the time gorged with blood. 



It seems probable that if an ungulate fought violently 

 with horns covered with velvet, one of two results would 

 follow : either the skin and periosteum would be torn, or the 

 skin would be hardened by the friction. Possibly this is the 

 true explanation of the different courses taken by the evolution 

 of the horns in the Bovidae and the Cervidae. In the former 

 a slowly developing horn, having a tough and not very vascular 

 skin, was subjected to frequent but not very violent friction, 

 till the skin became a horny covering. Horn is thickened 

 epidermis, and the development of horn therefore implies 

 that the true derma and periosteum were not lacerated. But 



1 Second edition, New York, 1881. 



