FORM OF PERMANENT TEETH. MOLARS. 783 



one tubercle distinctly marked, i. e., the external, and in that case approaches 

 in figure to a canine tooth. 



The molar teeth, true or large molars, or multicuspid teeth, are twelve 

 in number, and are arranged behind the bicuspid teeth, three on each 

 side, above and below. They are distinguished by the large size of the 

 crown, and by the great width of its grinding surface. The first molar 

 is the largest, and the third is the smallest, in each range, so as to pro- 

 duce a gradation of size in these teeth. The last molar in each range, 

 owing to its late appearance through the gums, is called the wisdom- 

 toothy dens sapientise. 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 

 it nearly square in the lower teeth, and rhomboid al in the upper, the 

 corners being rounded off : it is not smooth, but is provided with four or 

 five trihedral tubercles or cusps (whence the name of multicuspidati), sepa- 

 rated from each other by a crucial depression. The upper molars have 

 four cusps situated at the angles of the masticating surface ; of these the 

 internal and anterior 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 tubercles are usually blended together. 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 cusps, and 

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

 teeth, in which the crown is smaller and rounder than in the others. The 

 fangs of all 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 turned towards the antrum of the superior max- 

 illa ; and a third or internal fang, which is larger and longer, and is directed 

 towards the palate, the posterior border of which extends as far back as that 

 of the posterior external fang. This third fang is often slightly grooved, 

 especially when the two internal cusps are very distinct, and sometimes it 

 is divided into two smaller fangs. The two anterior molars of the lower 

 jaw have each two fangs, one anterior, the other posterior, which are broad, 

 compressed, and 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, or 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 irregu- 

 larly : this composite fang sometimes shows traces of subdivision, and there 

 are occasionally two fangs in the lower tooth and three in the upper. 



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

 their crowns, are fitted for bruising, crushing, and grinding the food in 

 mastication. 



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

 not broken by any intervals, as is the case in the dental apparatus of 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 overhang 

 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 



