108 A MANUAL OF ANATOMY 



molar type; and (2) its lingual cusp is stout, and not so much de- 

 pressed as that of the first lower bicuspid. 



The second lower bicuspid has occasionally two fangs. 



The Molars {MuUicuspidate Teeth). — There are ti&elve molar, or 

 grinding teeth — three in each upper jaw, and three in each half of 

 the lower jaw. 



First and Second Upper Molars. — The crown is somewhat square, 

 the angles being rounded off. The grinding surface is furnished 

 with four cusps, situated at each angle of the square, two of them 

 being labial and two lingual. The anterior lingual cusp is the 

 largest, and it is connected with the posterior labial cusp by a stout 

 oblique ridge. The labial cusps are longer or more projecting than 

 the lingual cusps, which applies to all the upper molars. The 

 fissure between the two labial cusps and that between the two 

 lingual cusps appear for a short distance on the labial and lingual 

 surfaces of the crown respectively. The posterior lingual cusp is 

 occasionally suppressed. 



The root has three fangs — two labial and one lingual. The lingual 

 fang is the largest and most divergent, its direction being obliquely 

 inwards towards the tongue. 



Third Upper Molar. — This tooth is subject to much variety. Its 

 crown is usually of smaller size than that of the first and second. 

 The two lingual cusps of the crown are frequently confluent. The 

 three fangs are blended together to form a tapering cone. 



Lower Molars. — The first lower molar is the largest. The crown 

 is somewhat square, and its grinding surface is provided with five 

 cusps. Four of these are placed at the angles of the square, and 

 are separated from each other by a crucial fissure. The posterior 

 limb of this fissure bifurcates, and the fifth cusp lies in the angle of 

 bifurcation. This cusp may be in the median Hne, but it usually 

 lies towards the labial aspect, from which aspect it can readily be 

 seen. The lingual cusps are longer or more projecting than the 

 labial cusps, which applies to all the lower molars. The fissure 

 which separates the two labial cusps usually passes for a short 

 distance on to the labial surface of the crown, but the fissure be- 

 tween the two lingual cusps only occasionally passes on to the 

 lingual surface of the crown. The root has two fangs — anterior and 

 posterior. Each fang is much compressed from before backwards, 

 and in most cases each presents a slight backward curve. 



The second lower molar bears a general resemblance to the first. 

 The fifth cusp is often absent, and, when present, it is of small size. 

 The two fangs of the root are frequently blended together. 



The third lower molar is of larger size than the third upper molar. 

 Its crown is large, and is usually provided with five cusps. Its root 

 may have two separate fangs, or these may be confluent. In the 

 latter case a groove indicates the double condition of the root. 



Dental Arches. — The alveolar borders of the superior and inferior 

 maxillary bones, and the upper and lower teeth, are so disposed as 

 to form two, almost similar, curves. When the mouth is closed, 



