Horns in general are hollow at their point of attachment to the
bone which juts out from the head inside the horn, but they have a
solid portion at the tip, and they are simple and undivided in
structure. In the case of the stag alone of all animals the horns
are solid throughout, and ramify into branches (or antlers). And,
whereas no other animal is known to shed its horns, the deer sheds its
horns annually, unless it has been castrated; and with regard to the
effects of castration in animals we shall have much to say
hereafter. Horns attach rather to the skin than to the bone; which
will account for the fact that there are found in Phrygia and
elsewhere cattle that can move their horns as freely as their ears.