THE TEETH OF MAN. 15 



and posterior (mesial and distal) edges of the grinding 

 surface. 



The root is single, and much compressed from side to 

 side : very often, however, it is double for the greater part 

 of its length, and if not so divided is often marked by a 

 groove upon each side indicating a tendency towards such 

 division. The outer border of the root is also often marked 

 by a longitudinal furrow, which may amount to complete 

 division. In fact a bicuspid may have three perfectly dis- 

 tinct roots, like a molar, or it may have any form of root 

 intermediate between this and its typical single laterally- 

 flattened root. The first bicuspid is more variable in respect 

 of its roots than the second. 



The second upper bicuspid differs from the first in that 

 the difference in size between its outer and inner cusps is 

 less, the inner cusp being relatively considerably larger, 

 and, indeed, often preponderating over the labial cusp in 

 length. 



The pulp cavity in the crown is furnished with distinct 

 cornua ; at the neck it is very much flattened from side to 

 side, being often reduced to a mere fissure, which is how- 

 ever considerably larger at its two extremities than in its 

 middle. Hence the pulp cavity of an upper bicuspid is 

 difficult to fill j a difficulty again increased by the impos- 

 sibility of always discovering what number of fangs it has, 

 as their division sometimes takes place rather high up. 



Lower premolars are smaller teeth than those of the 

 upper jaw, and are quite distinct in shape. The outer or 

 labial cusp is bent inwards, and the labial surface of the 

 crown is very convex. The inner cusp is but feebly deve- 

 loped, and is connected with the outer by a low ridge ; it is 

 also narrow. 



The root is rounded, a little larger on its outer side than 

 on its inner, and tapers regularly towards its point ; the 

 pulp cavity is cylindrical at the neck, and also tapers regu- 



