MAMMALIA. 393 
places are called callosities. The end of the snout and the under surface 
of the toes want the hair in most of the mammals. The Cetacea have no 
hairs at all, and the Sirenid@ only at the margin of the snout and eyelids. 
Often the color changes according to the age, the climate, the locality, 
and the season of the year. In domesticated animals the color of the hair 
undergoes quite as many variations, and becomes also often longer or 
shorter, or it crisps like wool, although the hair may have been straight in 
the original stock of their race. Many mammals are provided with append- 
ages on their forehead, which may be presented under three types: horns, 
as in sheep and oxen; antlers, as in deer ; and agglutinated hairs, as in the 
giraffe and rhinoceros. Horns proper are so placed as to cover a horn 
core, a projection of the frontal bone. They increase in size every year, 
without being ever shed, and usually occur in both sexes. They are found 
in oxen, sheep, goats, antelopes, charhois, &c. 
The horns of deer are more properly termed antlers, in French called 
bois, or wood. ‘These are entirely solid, and are shed every year, to give 
place to a larger pair. The female rarely possesses them ; an exception 
is, however, found in the reindeer. The annual shedding and growth of 
the horns is very curious and interesting. We take the example of the 
deer, according to Bell’s History of British Quadrupeds. “Let it be stated 
first that the horn is placed upon a protuberance on each side of the frontal 
bone: the part which rests upon the bone, forming the base of the horn, is 
surrounded by a rough protuberant ring called the burr. Now the principal 
stem of the horn has the name of the beam; the irregular divisions near its 
extremity are termed branches, and are distinguished from the true antlers, 
which are the essential branches belonging to the species, and stand gene- 
rally forwards, of which the first is called the brow-antler, the next the bez- 
antler, and the third the royal; the crown is termed the surroyal. By the 
number of these antlers, and other marks in the development of the horns, 
the age of the animal may be nearly ascertained. The growth of the horns 
is an astonishing instance of the rapidity of the production of bone under 
particular circumstances, and is certainly unparalleled in its extent in so 
short a period of time. A full grown stag’s horn probably weighs twenty- 
four pounds, and the whole of this immense mass of true bone is produced 
in about ten weeks. During its growth, the branches of the external caro- 
tid arteries, which perform the office of secreting this new bone, are con- 
siderably enlarged, for the purpose of conveying so large a supply of blood 
as is necessary for this rapid formation. These vessels extend over the 
whole surface of the horn as it grows. and the horn itself is at first soft and 
extremely vascular, so that a slight injury, and even merely pricking it, 
produces a flood of blood from the wound. It is also protected at this time 
with a soft hairy or downy coat, which is termed the velvet; and hence 
the horns are said to be in the velvet during their growth. When com- 
pleted, the substance of the horns becomes dense, the arteries become obli- 
terated, and the velvet dries and falls off in shreds, a process which is 
hastened by the animal rubbing his horns against the branches of a tree. 
The horns remain solid and hard, constituting the most effectual weapons 
597 
