252 ELEMENTARY ANATOMY. [LESS. 



the fourth, however, in having its fang often cleft for a con- 

 siderable distance from its end. 



The sixth upper tooth is the largest of the whole series. 

 It has a flattened grinding surface, with four cusps, and an 

 oblique ridge connecting the front inner cusp with the hind 

 outer one. The fangs are three in number, two being placed 

 on the outer side, and one on the inner. 



The seventh upper tooth is quite like the sixth. 



The eighth upper (or wisdom) tooth is less large, though 

 essentially similar. The two inner cusps of its crown are 

 blended together, and its fangs are generally united into a 

 single, irregular, conical mass. 



The three teeth last described are all termed (for a reason 

 which will shortly appear) true molars. In the lower jaw 

 the first two teeth are similiar in shape to the first two teeth 

 of the upper jaw, whence they are also called incisors. 

 They have also each a single fang. 



The third lower tooth is pointed and conical, and has 

 a single root like the third tooth of the upper jaw. It there- 

 fore bears a similar name, and the lower canine should have 

 its apex within and slightly in front of the crown of the upper 

 canine. 



The fourth and fifth teeth of the lower jaw are called bi- 

 cuspid molars, like the fourth and fifth teeth of the upper 

 one. Sometimes, however, the fourth has only a single 

 cusp, and it is more canine-like than the one answering to 

 it above. 



The sixth and seventh teeth of the lower jaw are called 

 true molars. Each bears five cusps, three on the outer side 

 of each crown and two on the inner. The fangs are two to 

 each, but each fang is vertically grooved. 



The eighth lower tooth, or lower wisdom tooth, is also a 

 "true molar," but differs from the two last described in 

 having, generally, its fangs blended together, and in having 

 its crown smaller than the others and more rounded. 



The human- milk-teeth are twenty in number : two inci- 

 sors, one canine, and two molars, on each side of each jaw. 



They resemble the permanent teeth, but the last molar, 

 both above and below, does not resemble the fifth tooth of 

 the permanent dentition (and which is its vertical successor), 

 but it resembles the first true molar in each case, though it 

 has nothing to do with the formation of this tooth, of which 

 it is, as it were, the prototype. 



The details of the succession of the teeth belong rather to 



