284 SKELETON OF THE BABBIT 



bone. Along the anterior surface the 

 enamel is thick, and folded so as to form 

 a longitudinal groove. Behind and at the 

 side it is much thinner, and hence wears 

 away more rapidly, rendering the cutting 

 edge chisel-shaped. 

 j8. The posterior incisors, which are placed im- 

 mediately behind the anterior ones, are 

 much smaller, and slightly curved. 



ii. The grinding teeth form a set of six teeth on 

 each side, borne by the maxilla, and divisible 

 into two groups. 



a. The premolars are the three anterior grinders 

 of each side, and are distinguished from 

 the posterior ones by the fact that, like the 

 incisors, they are preceded in early life by 

 ' milk ' or deciduous teeth, which in the 

 rabbit are shed before birth. 



Each premolar is flattened from before 

 backwards, and each of the two hinder ones 

 has a deep groove along its outer surface 

 which carries the enamel almost across the 

 tooth, giving rise to a prominent ridge on 

 the grinding surface. 



/8. The molars are the three posterior grinders 

 on each side ; they differ from the premolars 

 in having no deciduous predecessors. The 

 first two are similar to the premolars ; the 

 last is small and not grooved. 



b. The teeth of the lower jaw. 



i. The incisors are two in number, and project for- 

 wards from the anterior end of the mandible. 

 They are similar to the large upper incisors, but 

 are less strongly curved and are not grooved : 

 the alveoli in which they are lodged extend 

 back in the jaw as far as the anterior grinders. 



ii. The grinding teeth form a set of five on each 



