352 THE MECHANICAL FUNCTIONS. 



elevated by the growth of a tubercle from the subjacent 

 bone: this tubercle is at first a cartilage, and after it has at- 

 tained a certain size, becomes ossified, and grows like other 

 osseous structures, first shooting into the form of a length- 

 ened cylinder, and then dividing into branches. It is fol- 

 lowed 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 mem- 

 brane of the antler, or periosteum, still continuing to sup- 

 ply it with the materials required for its growth and conso- 

 lidation, deposite so great an abundance of bony matter, that 

 its enlargement 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 

 kingdom of so rapid a growth; which is the more remarka- 

 able from its occurring in a small part of the system, and 

 in a bony structure. 



After the antler has attained its full size, a deposition of 

 osseous substance still continuous at its base, around the 

 trunks of the arteries which are proceeding along the invest- 

 ing membrane of the bone for the purpose of conveying 

 nourishment. 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 dimi- 

 nishes their capacity of conveying blood, and they at length 

 become entirely obliterated. The bone, no longer receiving 

 a superabundant nourishment, ceases to grow; the integu- 

 ments which covered it, decay, and becoming dry and shri- 

 velled, are torn by rubbing against trees, and peel o^ in long 

 shreds, leaving the antler exposed, which, by the continued 

 effects of the same kind of friction, soon acquires a polished 

 surface. 



During many months, the antler being sufficiently nourished 

 by its own interior vessels, continues in a living state, and 

 preserves its connexion with the system. But, at length, the 



