Animal Dentition 111 
no reduction in number and attain great development in size. The cheek-teeth, on 
the other hand, tend to become diminished in number, although such as remain are 
specially modified for thei particular function, and thus assume a form totally different 
from those of the herbivorous species. A notable instance of this type of specialisation 
(as it is called by naturalists) is afforded by the lion and other members of the cat tribe. 
Among existing carnivora the group which presents the smallest departure from 
the primitive type of dentition is perhaps that of the dogs, wolves, and foxes. As 
shown in the figure of the fox’s skull (making allowance for the abnormal duplication 
of the upper tusks), the three pairs of incisors and the single tusk are well developed 
in both jaws; and behind these come six pais of cheek-teeth in the upper and seven 
in the lower jaw. The dentition therefore only falls short of the typical number of 
forty-four by two, this diminution being due to the loss of the last pair of upper 
molars. Even these are present in one peculiar African member of the family—the 
long-eared fox. The earlier cheek-teeth of the dog and fox are not very unlike the 
primitive type; but the fourth tooth behind the upper tusk and the fifth behind 
the lower one are much longer and larger than those in front of them, and have their 
crowns furnished with sharp flattened blades, which cut 
against one another like a pair of scissors. To these 
specially modified teeth the name of carnassials, or flesh- 
teeth, has been appropriately given. The teeth behind the 
flesh-tooth in each jaw of the dog and fox have broad and 
expanded crowns, mainly adapted for mastication. 
An examination of the lower flesh-tooth 
of either of the animals last mentioned will 
serve to show that only its front half is 
designed for a scissors-like mode of action, 
the hinder portion of the crown being flat 
and tuberculated, and thus adapted for 
mastication. In the lon (Fig. 4), as well 
as in other members of the cat tribe, the SA it SOL ae 
carnassial teeth in both jaws are entirely : an ~ tue y Psat 
adapted for cutting, and consist wholly of XG \\W ‘ "@ 
blade. They are, moreover, relatively larger Fig. 5. 
in proportion to the other cheek-teeth, Figs. 5 and 6. Side view of Dentition of Bear and the last 
of which latter the number is much less See atierenae ees 
than in the dog tribe; while the tusks are likewise very large and powerful. ‘This 1s, 
in fact, the most perfectly-developed type of carnivorous dentition now existing, the 
powerful tusks being adapted to seize and hold prey and make the first incisions in 
the carease. The incisors form strong pincers to strip the flesh from the bones, while 
the flesh-teeth sever the strips of flesh into convenient lengths for bolting whole. 
Unlike a dog, a cat never masticates its food at all; and this is the reason why the 
former animal takes so readily to a diet of biscuits, while the latter can only be 
persuaded with difficulty to eat this kind of food. In an extinct group of cats—the 
sabre-toothed tigers—the development of the flesh-teeth and tusks was much greater 
than in the lion, the latter teeth being in some cases seven or eight inches in length, 
with serrated edges. Such tusks would close the aperture of the mouth if opened only 
to the usual extent, and it is probable that these fell creatures had the power of 
lowering the lower jaw at a right angle to the palate, and then using their upper 
tusks to stab their victims. 
In the bear tribe the flesh-teeth are much diminished in size, and haye almost 
completely lost their cutting form and scissors-like action, as is shown in Fig. 5, where 
\ Sa SS r 
