1544 



HUMAN ANATOMY. 



Often the cingxilum of the incisors is represented merely by the tubercle. There are 

 all kinds of intermediate stages between this and a nearly plane surface. Sometimes 

 the tubercle is triple. The fang is nearly conical, and usually has an outward slant. 

 The superior lateral incisors are more cusp-shaped, the angles, especially the outer, 

 tending to be rounded. The lingual surface is less plane than in the median incisors 

 and the cingulum larger. Sometimes it is almost a distinct cusp. The fang is also 

 conical, with an outward inclination. 



The inferior incisors are smaller than the superior, and the median ones the 

 smallest of all. The crowns broaden from the neck to the edge. This feature is 

 more marked in the lower races, and still more in apes. The labial surface is more 

 nearly plane than in the upper ones ; the lingual surface is more even. The 

 cingulum is small, often not very evident. The angles of the free edge are sharper 

 than those of the upper jaw, excepting the outer one of the lateral tooth, which is 

 generally rounded. T\\q fangs are compressed from side to side and their tips turn 

 a little away from the median line. This is particularly true of the lateral one, but 



Fig. 1298. 



Fig. 1300. 



A B 



Unworn surfaces of upper 

 and lower permanent incisor 

 teeth, lingual aspect. X 2. 



Median incisor teeth 

 of left side, labial {A) 

 and lateral {B) aspects. 

 (Leidy.) 



Temporary incisor 

 teeth of left side. A, 

 median ; B^ lateral in- 

 cisors. {Leidy.) 



is a constant feature of neither. The sides of the fangs are often grooved. The 

 external groove is the deeper, and when only one is present it is on that side. 



The pziip-cavity is relatively large in the superior median incisors, in which it 

 presents three expansions towards the free edge. It is smaller in the others, and has 

 usually but two distinct diverticula. The canal of the lower teeth, especially when 

 the roots are deeply grooved, often divides below the pulp-cavity into an anterior 

 and a posterior branch, which usually reunite before reaching the tip of the fang.^ 



The upper incisors occupy in all more space than the lower, which is due chiefly 

 to the great size of the upper median ones. In the lower jaw the median incisors 

 are the smaller, but there is no great difference between them and the laterals. The 

 superior laterals are but slightly larger than those below them. 



The temporary incisors differ only slightly, save in size, from the permanent 

 ones. The cages, however, are originally straight, except those of the inferior median 

 ones, which show the irregularities.^ 



The Canines. — These, called by the Germans the " corner teeth" as marking 

 the point where the alveolar arch changes direction most suddenly, are characterized 

 by a crown with a single cusp, a long conical root somewhat compressed laterally and 

 marked by a groove on each side. The crown, convex on the labial side, expands 



^ Miihlreiter : Anatomic des Menschlichen Gebisses, Leipzig, 1891. 



" Zuckerkandl : Anatomic der Mundhohlc, mit besondere Beriicksichtigung dcr Zahne, 

 Wien, 1891. 



