238 
ZOOLOGY. 
wliich has but one digit or toe and walks on its single toe- 
nail. 
Mammals have larger brains, and a more roomy brain- 
cavity in the skull than any of the lower animals, while 
the teeth are of four kinds, i.e., molars, premolars, canines, 
and incisors. 
Many mammals, especially those that chew the cud, as the 
leer, ox, rhinoceros, etc., are armed with horns. There are 
two kinds of horns — those with a bony core surrounded with 
a horny case of skin as in the deer; while in others, as the 
antelopes, sheep, goats, and oxen, the horns are hollow. 
Fia. 281.— Teeth of a Mammal. The incisors are placed in front of the large 
conical canine teeth; 2, 3, premolars; m, 1-4, four molar teeth. 
In most horned mammals the horns are not shed; in the 
deer they drop off every year; in the prong-horned ante- 
lope the horns are also shed yearly. 
It is a rule that the males of such animals as are provided 
with tusks or horns always fight for the possession of the 
female. It is so with bulls, deer, elephants, boars, and 
rams; at the same time these are organs of defence by 
which the males protect their family, flock, or herd. On 
the other hand, in tlie female rhinoceros, some antelopes, 
the reindeer, as opposed to the other deer, some sheep and 
goats, etc., the horns are nearly as well developed as in the 
o])posite sex. The modes of attack are various: the ram 
charges and butts with the base of his horns, the domestic 
