S6 



AGE OF THE DOMESTIC ANIMALS. 



replace the temporary molars, are known as pre-molars, and the 

 last three as the post-molars. Each row of six molars forms a 

 branch of the dental arch, which in the upper jaw is slightly 

 convex to the outer side, while in the lower jaw it is perlectly 

 straij^ht, with the anterior extremities inclined toward the other, 

 so that they form a sort of V, and are overlapped by those of 

 the upper jaw. 



Fig. 28. 



A, transverse section of the lower jaw, showing the third temporary molar 

 and its relation to the permanent molar which replaces it. B, third inferior per- 

 manent molar, capped by the worn temporary molar. 



The permanent molars hav^e the shape of quadrangular 

 prisms flattened from side to side, except the first and sixth, 

 wliich are triangular. 



Superior Molars. — -The posterior faces are almost smooth, 

 except in the sixth molar, where the face is replaced by a blunt 

 edge ; the anterior faces are also smooth, except that of the first 

 molar, which is replaced by a sharp border. 



