1116 



THE DIGESTIVE SYSTEM. 



cutting edge is worn away, or becomes bevelled, on the lingual aspect in the 

 former, but on the labial aspect or summit in the latter. The upper, and par- 

 ticularly the central upper incisors, are of large size, and slope somewhat forwards ; 

 whilst the lower incisors, all of nearly equal size, are much smaller being 



2nd molar 2nd premolar Canine Central incisor 



1st premolar ^ Lateral incisor | 



3rd molar 



1st molar 



3rd molar 



1st molar 



1st premolar t^ Lateral incisor 

 2nd molar 2nd premolar Canine Central incisor 



FIG. 881. THE PERMANENT TEETH OF THE RIGHT SIDE, LABIAL ASPECT. 



The upper row shows the upper teeth, the lower row the lower teeth. The wide vertical " labial ridge " is 

 distinct on the upper canine and premolar teeth. 



the smallest of all the teeth and are placed vertically. The roots of the incisors 

 are single, though a groove is occasionally seen on each side, suggesting a division. 



The central upper incisors are very much larger than the lateral upper incisors (Fig. 881), but in 

 the mandible the opposite is the case, the lateral incisors being slightly the'larger. In all incisors 



Central incisor Canine 2nd premolar 



Lateral incisor /V 1st premolar | 1st molar 



2nd molar 



3rd molar 



Lateral incisor J* 1st premolar J 1st molar 3rd molar 



Central incisor Canine 2nd premolar 2nd molar 



FIG. 882. THE PERMANENT TEETH OF THE RIGHT SIDE, LINGUAL ASPECT. 



The upper row shows the upper teeth, the lower row the lower teeth. The cingulum is distinct on the upper 

 incisors and both canines, the lingual tubercle on the upper lateral incisor and the upper canine. 



the lateral angle of the crown is more rounded than the medial. The concave lingual surface 

 of the crown in the upper incisors is usually limited towards the gum by a A -shaped ridge 

 (Fig. 882), known as the cingulum. The two limbs of the A are continued up along the sides 

 of the lingual surface, whilst the apex is turned towards the gum ; and here, particularly in 

 the lateral incisor, there is often developed a small lingual tubercle (Fig. 882). The cingulum is 

 rarely found on the lower incisors. 



The roots of the upper incisors and canines are conical and rounded (the lateral incisors and 

 canines not so distinctly as the central incisors) (Fig. 881), whilst those of the mandible are 

 flattened from side to side (medio-laterally). 



