SPECIAL CHARACTER OF THE PERMANENT TEETH, 



303 



Fiff. 202. 



d 



Vi". 202. 



-Incisor Teeth of 

 AND Lower Jaws. 



THE Upper 



adapted for cutting or dividincj the food. Their crowns are chisel- 

 shaped (c), and have a sharp horizontal cutting edge, which by con- 

 tinued use is bevelled off" behind 

 in the upper teeth, but in the 

 lower ones is worn down in front, 

 where it comes into contact with 

 the over-lapping edges of the 

 upper teeth. Before being sub- 

 jected to wear, the horizontal 

 edge of each incisor is marked 

 by three small prominent points, 

 separated by two slight notches 

 (fig. 202, d). The anterior sur- 

 face of the crown is slightly 

 convex, and the posterior con- 

 cave. The fan(/ is long, single, 

 conical, and compressed at the 

 sides, where it sometimes though 

 rarely presents a slight longitu- 

 dinal furrow (as in c). 



The lower incisor teeth are 

 placed vertically in the jaw, but 

 the corresponding upper teeth 

 are directed obliqttely forwards. 

 The upper incisors are, on the 

 whole, larger than the lower ones. 

 Of those in the upper jaw the 

 central incisors are the larger ; 

 but in the lower jaw, the central 

 incisors are the smaller, and are, 

 indeed, the smallest of all the 

 incisor teeth. 



The canine teeth, (fig. 20 P.), 

 four in number, are placed one 



on each side, above and below, next to the lateral incisors. They are 

 larger and stronger than the incisor teeth. The crown is tliick and 

 conical, convex in front and hollowed behind, and may be compared 

 to that of a large incisor tooth the angles of which have been removed, 

 so as to leave a single central point or cus^i, whence the name cuspidate 

 applied to these teeth. The point always becomes worn down by use. 

 The fang of the canine teeth is single, conical, and compressed at 

 the sides : it is longer than the fangs of any of the other teeth, and is 

 so thick as to cause a corresponding prominence of the alveolar arch : 

 on the sides it is marked by a groove, an indication, as it were, of the 

 cleft or division which appears in the teeth next behind. 



The upper canines, popularly called the cijc-tceUi, are larger than the 

 iOwer, and in consequence of this, as well as of the greater width of the 

 upper range of incisors, they are thrown a little farther outwards than 

 the lower ones. In the dog-tribe, and in the carnivora generally, these 

 teeth acquire a great size, and are fitted for seizing and killing prey, 

 and for gnawing and tearing it when taken as food. 



The bicuspids, also called jjremolars, are four in each jaw ; they 

 are shorter and smaller than the canines, next to which they are 



«, front view of the upper and lower 

 middle incisors ; b, front view of the upper 

 and lower lateral incisors ; c, lateral view 

 of the upper and lower middle incisors, 

 showing the chisel shape of the crown ; 

 a groove is seen marking slightly the fang 

 of the lower tooth ; d, the upper and 

 lower middle incisor teeth before they have 

 been worn, showing the three points on 

 the cutting edge. 



