Of horned

animals the deer alone has a horn, or antler, hard
and solid throughout. The horns of other animals are hollow for a
certain distance, and solid towards the extremity. The hollow part
is derived from the skin, but the core round which this is wrapped-the
hard part-is derived from the bones; as is the case with the horns
of oxen. The deer is the only animal that sheds its horns, and it does
so annually, after reaching the age of two years, and again renews
them. All other animals retain their horns permanently, unless the
horns be damaged by accident.