THE TEETH 231 



There are no fewer than six distinct openings into the 

 front part of the pharynx — four in pairs, and two single 

 ones in the middle line. The two pairs are, in front, the 

 hinder openings of the nasal cavities ; and at the sides, 

 close to these, the apertures of the EjUStachian tubes 

 (g). The two single apertures are, the hinder opening of 

 the mouth between the soft palate and the epiglottis ; and, 

 behind the epiglottis, the upper aperture of the respira- 

 tory passage, or the glottis. 



Each of the thirty-two teeth which have been mentioned 

 consists of a crown which projects above the gum, and 

 of one or more fangs, which are embedded in sockets, or 

 what are called alveoli, in the jaws (see Fig. 3). 



The eight teeth on opposite sides of the same jaw are 

 constructed upon exactly similar patterns, while the eight 

 teeth which are opposite to one another, and bite against 

 one another above and below, though similar in kind, 

 differ somewhat in the details of their patterns. 



The two teeth in each eight which are nearest the 

 middle line in the front of the jaw, have wide but sharp 

 and chisel-like edges. Hence they are called incisors, 

 or cutting teeth. The tooth which comes next is a 

 tooth with a more conical and pointed crown. It answers 

 to the great tearing and holding tooth of the dog, and is 

 called the canine or eye-tooth. The next two teeth have 

 broader crowns, with two cusps, or points, on each crown, 

 one on the inside and one on the outside, whence they 

 are termed bicuspid teeth, and sometimes false grinders. 

 All these teeth have usually one fang each, except the 

 bicuspid, the fangs of which may be more or less com- 

 pletely divided into two. The remaining teeth have two 

 or three fangs each, and their crowns are much broader. 

 As they crush and grind the matters which pass between 

 them they are called molars, or true grinders. In the 

 upper jaw their crowns present four points at the four 

 corners, and a diagonal ridge connecting two of them. 

 In the lower jaw the complete pattern is five-pointed, 



