THE ALIMENTARY CANAL (225 
the crown, which projects above the gums, and a narrow neck 
connecting the two. The root is composed of one or more 
separate fangs; the crown bears one or more points or cusps. 
At the cranial end of each jaw are six incisor teeth (Figs. 
93 and 94, a). These are imbedded in the alveolar borders of 
the premaxillaries and the man- 
dible. The incisor teeth are 
small, with a crown bearing a 
sharp edge which is notched so 
as to form three minute cusps. 
The root of each has a single 
fang. The lateral inciscrs are 
the largest in each jaw, and 
those of the upper jaw are larger Fic. Sa Weare J Jae, sia Boor 
than those of the lower. a, incisors; 6, canine; ¢, an pre- 
Caudad of the incisors, and molar; d, second premolar; ¢, third pre- 
in the upper jaw separated from ™l@" 4 molar. 
them by a slight interval, are the canines (4), two in each jaw. 
These are long, strong, pointed teeth, deeply imbedded in the 
mandible and maxillaries, their large sockets causing a rounded 
swelling on the external surface of the bones. Each has a 
single fang and a single cusp. When the mouth is closed the 
upper canines lie laterocaudad of the lower ones. 
Caudad of the canines there is in each jaw a considerable 
interval free from teeth: this is called the diastema. Caudad 
of the diastema are the premolar teeth, three pairs (¢, d, ¢) in 
the upper jaw and two pairs (c, d) in the lower jaw. These 
teeth are compressed sideways, and those of the lower jaw fit 
inside of those of the upper jaw. In the upper jaw (Fig. 93) 
the first premolar (c) is small and usually has but a single cusp 
and asingle fang, though occasionally there is a small supple- 
mentary cusp and fang. The second premolar is larger (2); 
it has a large central cusp, with a single smaller cranial cusp 
and two small caudal cusps, making four in all. This tooth 
has two fangs. The third premolar (¢) is the largest tooth in 
the jaws; it has three large cusps in longitudinal series and a 
small cusp lying on the medial side of the first one in the row. 
Its root has three fangs. The molar tooth (/) of the upper 
