510 THE MECHANICAL FUNCTIONS. 



It is followed in its elongation by the skin, which 

 during the whole time that the antler is growing 

 is extended over it in every part, forming what 

 is called, from the delicate investment of hair, 

 its velvet coat. The blood-vessels of the proper 

 membrane of the antler, or periosteum, still con- 

 tinuing to supply it with the materials required 

 for its growth and consolidation, deposit so great 

 an abundance of bony matter, that its enlarge- 

 ment is exceedingly rapid. The whole antler* 

 which often weighs nearly thirty pounds, has 

 been known to be completely formed in ten 

 weeks from the time of its first appearance. 

 There is no other instance in the animal king- 

 dom of so rapid a growth ; which is the more 

 remarkable from its occurring in a small part 

 of the system, arid in a bony structure. 



After the antler has attained its full size, a 

 deposition of osseous substance still continues at 

 its base, around the trunks of the arteries which 

 are proceeding along the investing membrane of 

 the bone for the purpose of conveying nourish- 

 ment. The accumulation of this substance raises 

 a ring, called the burr, round that part of the 

 antler: and by encroaching on the arteries 

 themselves, it gradually diminishes their capa- 

 city of conveying blood, and they at length be- 

 come entirely obliterated. The bone, no longer 

 receiving a superabundant nourishment, ceases to 

 grow ; the integuments which covered it, decay, 

 and becoming dry and shrivelled, are torn by 



