48 
GUIDE TO THE 
As incidentally mentioned above, the ruminants are divi¬ 
ded into two sections according as their horns are hollow 
or solid. The former horns are developed as one pair with 
the exception of the four-horned antelope of India, Teira - 
ceros quadricornis , and they consist of a solid core prolong¬ 
ed outwards from the frontal bone and covered with a 
sheath of horn. These horns are simple, unbranched 
structures, except in the Pronghorn Antelope, Antilocapra 
americana , a North American ruminant in which each horn 
has a short branch, and it is this animal alone, among the 
hollow-horned ruminants, that sheds its horns at intervals, 
as in all the others, these structures persist throughout life. 
These horns have the power of repairing injuries ; and in the 
first species in the series of these ruminants, there is a 
female wild sheep, Ovis cycloceros , one horn of which not 
only lost its sheath, but also had the core injured, and yet 
the injury to the core was repaired, and the sheath in time 
was completely restored ; horn being simply a thickening of 
the outer skin or epidermis. Horns of this kind may either 
be straight, curved, spirally twisted, or ringed. 
Very different from these persistent epidermal horns, 
are the long horns of the deer which are bony antlers 
not covered by horn, and which are shed every year. 
These structures are developed from processes of the front¬ 
al bone covered with skin and hair. After the animals have 
attained a certain age these processes begin to grow, and 
whilst so doing they are full of blood-vessels and from the 
active flow of blood to them, their temperature is much 
higher than that of the rest of the external surface of the 
body. As growth advances, the part from which the horns 
sprang and which is called the pedicel , becomes marked off 
from the horns by a circular thickening called the burr> 
