AEUAXGEMEXT OF THE TEETH IX THE JAAV. 305 



molar is the largest, and the third is the smallest, in each range, so 

 as to produce a gradation of size in these teeth. The last of the 

 range, owing to its late appearance through the gum, is called the 

 wisdom-tooth, dens sapientiaj. The crowns of the molar teeth are low 

 and cuboid in their general form. Their outer and inner surfaces are 

 convex, but the crowns are rather flattened before and behind. The 

 grinding surface is nearly square in the lower teeth, and rhomboidal in 

 the upper, the corners being rounded off ; it bears four or five trihedral 

 tubercles or cusps (whence the name onulticuspidati), separated from 

 each other by a crucial depression. The upper molars have four cusps 

 situated at the angles of the masticating surface ; of these the anterior 

 internal cusp is the largest, and is frequently connected with the 

 posterior external cusp by a low oblique ridge. In the upper wisdom- 

 teeth, the two internal cusps are usually blended. The crowns of the 

 lower molars, which are larger than those of the upper, have five cusps, 

 the additional one being placed between the two posterior ones, and 

 rather to the outer side ; this is especially evident in the lower wisdom- 

 teeth, in which, however, the crown is smaller and rounder than in 

 the others. The fanys of the molar teeth are multiple. In the two 

 anterior molars of the upper jaw, they are three in number, viz., 

 two placed externally, which are short, divergent, and directed towards 

 the antrum of the superior maxilla ; and a third or internal fang, 

 which is larger and longer, and is directed towards the palate, its 

 posterior border extending as far back as that of tlie posterior external 

 fang. This third fang is often slightly grooved, especially when the 

 two internal cusps of the crown are very distinct, and sometimes it is 

 divided into two smaller fangs. The two anterior molars of the loiver 

 jaw have each two broad, compressed fangs, one anterior, the other 

 posterior, which are grooved on the faces that are turned towards each 

 other, as if each consisted of two fangs fused together ; they have 

 an inclination or curve backwards in the jaw, and are slightly divergent, 

 but sometimes parallel, or even nearly in contact with each other ; more 

 rarely one or both of them is divided into two smaller fangs. In the 

 wisdom-teeth of both jaws the fangs are often collected into a single 

 irregular conical mass, which is either directed backwards in the substance 

 of the jaw, or curved irregularly ; this composite fang sometimes shows 

 ti'aces of subdivision, and there ai'e occasionally two fangs in the lower 

 tooth and three in the upper. 



The bicuspid and the molar teeth, from the breadth and uneven 

 character of their masticating surface, are fitted for bruising, crushing, 

 and grinding the food. 



The range of teeth in each jaw forms a nearly uniform curve, which 

 is not broken by any interval, as is the case in many animals, even 

 in the Quadrumana. The upper dental arch is rather wider than 

 the lower one, so that the teeth of the upper jaw slightly over- 

 hang those of the lower. This is owing principally to the fact that 

 the lower teeth are placed either vertically, as in front, or are 

 inclined somewhat inwards, as is seen behind and at the sides, while 

 the corresponding teeth of the upper jaw have an inclination forwards 

 in front, and outwards behind. AVhile there is a slight diminution in 

 the htjight of the crowns of the teeth fi-om the incisors backwards to 

 the wisdom-teeth, there is in man no abrupt change of level along the 

 range. In consequence of the large proportionate breadth of the upper 



VOL. II. X 



