THE MOLARS. 



627 



a. Superior Jaw. 



Faces. — Each of the molars has i\s posterior face almost plane. 



In the sixth, however, the face is constituted by a thick border, concave above 

 and behind. 



The anterior face presents the same general configuration, excepting in the 

 first molar, in which it is constituted by an almost rectilinear border, extending 

 from one extremity of the tooth to the other. 



The external face, E (Fig. 297), has two deep longitudinal grooves, separated 



E 



E. External face. 



Fig. 297. — Superior molar of re- 

 placement. 

 (Right side. Virgin tooth.) 



I /. Internal face. | E, I. Surface of friction. 



from each other by a salient ridge. That of the first molar has three of these 

 grooves, separated by two intermediary ridges. 



The internal face, I, is traversed by two grooves on the first molar and only 

 one for all the others. In the last five this groove is nearer to the posterior face 

 of the tooth. 



Extremities. — Of the two extremities, the one is free, the other incased. 

 The latter corresponds, properly speaking, to the roots of the teeth. 



The free extremity, or crown, EI, quadrilateral in general, is triangular in the 

 first and the sixth molars. It does not show the same disposition at all periods 

 of life. 



If the unworn tooth be first considered, there is seen an irregular surface, 

 somewhat resembling a Gothic S, whose " branches," turned inward, would cir- 

 cumscribe two deep cavities, more or less filled with cement, according to the sub- 

 ject. To the anterior of these branches is found annexed a secondary loop, which 

 is attached to it by a narrow pedicle. The external border of this surface of 

 friction, always more salient than the internal, is soon worn off, and the primitive 



