34 



AGE OF THE DOMESTIC ANIMALS. 



face, while the second and third teeth have two ; the internal 

 faces are irregular, slightly concave in their long axis, and show 

 canals very much less marked than those on the outside. 



The inferior teeth on their external face have a single gutter, 

 which is deepest in the first tooth and most shallow in the last ; 

 on their internal face they are irregularly grooved. All of the 

 milk-molars have a constriction or neck separating their crowns 



F I 



* 2 



Fig. 21. 

 The three superior temporary molars (right). F I, internal faee ; F E, external face. 



from their roots. They have each two roots, one anterior and 

 one posterior. Tliese are strong, convex outside and concave 

 inside ; each is hollowed hy an opening which reaches into the 

 tooth itself Just before being forced out by the permanent 

 teeth the roots are sometimes divided into little eminences by 

 the pressure of the irregularities on the crowns of the latter. 

 The free extremities of the virgin milk-molars are irregidar and 



