THE MOLARS. 



623 



concave internally. Each is penetrated by an opening which leads into the 

 interior of the tooth. These roots, sometimes divided into several somewhat 

 narrow points, when they are examined at a period approaching that when they 

 are shed, leave between themselves a mammillated surface which is moulded 

 upon the corresponding extremity of the replacing tooth. 



FIG. 293. The three superior deciduous molars (right side). 

 FI. Internal face. i FE. External face. 



All the molars of the superior jaw have three roots: one anterior and two 

 posterior in the first ; two external and one internal in the last two. These roots 

 are slightly diverging in such a manner that the tooth occupies more space in 

 the direction of this extremity than in the other. 



2d. Free Extremity. The free extremity, in the virgin teeth of both jaws, is 

 irregular, covered with eminences and hollow cavities ; but the external border 

 is always more salient than the internal in the superior, while it is the contrary 

 in the inferior. 



This extremity changes its aspect under the influence of the friction, and 

 ultimately constitutes a surface formed of planes alternately oblique in different 



