646 ORGANS OF DIGESTION. 



PERMANENT TEETH. 



The INCISORS or cutting teeth are so named from their presenting a sharp, cut- 

 ting edge, adapted for cutting the food. They are eight in number, and form the 

 four front teeth in each jaw. 



The crown is directed vertically, is wedge-like in form, being bevelled at the 

 expense of its posterior surface, so as to terminate in a sharp, horizontal cutting 

 edge, which, before being subject to attrition, presents three small prominent 

 points. It is convex, smooth, and highly polished in front ; slightly concave be- 

 hind, where it is frequently marked by slight longitudinal furrows. 



The neck is constricted. 



The fang is long, single, conical, transversely flattened, thicker before than 

 behind, and slightly grooved on each side in the longitudinal direction. 



The incisors of the upper jaw are altogether larger and stronger than those 

 of the lower jaw. They are directed obliquely downwards and forwards. The 

 two central ones are larger than the two lateral, and their free edges sharp and 

 chisel-like, being bevelled at the expense of their posterior edge ; the root is more 

 rounded. 



The incisors of the lower jaw are smaller than the upper; the two central 

 ones are smaller than the two lateral, and are the smallest of all the incisor 

 teeth. 



The CANINE TEETH (cuspidati) are four in number, two in the upper, and two 

 in the lower jaw; one being placed behind each lateral incisor. They are larger 

 and stronger than the incisors, especially the root, which sinks deeply into the jaw, 

 and causes a well-marked prominence upon its surface. 



The crown is large and conical, very convex in front, a little hollowed and un- 

 even posteriorly, and tapering to a blunted point or cusp which rises above the 

 level &f the other teeth. 



The root is single, but longer and thicker than that of the incisors, conical in 

 form, compressed laterally, and marked by a slight groove on each side. 



The upper canine teeth (vulgarly called eye-teeth) are larger and longer than the 

 two lower, and situated a little behind them. 



The lower canine teeth are placed in front of the upper, so that their summits 

 correspond to the interval between the upper canine teeth and the neighboring 

 incisor. 



The BICUSPID TEETH (small or false molars) are eight in number, four in each 

 jaw, two being placed immediately behind each of the canine teeth. They are 

 smaller and shorter than the canine. 



The crown is compressed from without inwards, and surmounted by two pyra- 

 midal eminences or cusps separated by a groove ; hence their name, licuspidate. 

 The outer of these cusps is larger and more prominent than the inner. 



The neck is oval. 



The root is generally single, compressed, and presents a tendency to become 

 double, as seen from the deep groove on each side. The apex is generally bifid. 



The upper bicuspids are larger, and present a greater tendency to the division 

 of their roots than the lower; this is especially marked in the second upper 

 bicuspid. 



The MOLAR TEETH (multicuspidati, true or large molars) are the largest of the 

 permanent set, and are adapted, from the great breadth of their crowns, for grind- 

 ing and pounding the food. They are twelve in number, six in each jaw, three 

 being placed behind each of the posterior bicuspids. 



The crown is nearly cubical in form, rounded on each of its lateral surfaces, 

 flattened in front and behind ; the upper surface being surmounted by four or five 

 tubercles or cusps (four in the upper, five in the lower molars) separated from 

 each other by a crucial depression ; hence their name, multicuspidati. 



