SPLANCHNOLOGY. 187 



end of the genio-glossus ; % its anterior, and °, its posterior fasciculus ; \ 

 median line of the tongue. 



8. The Teeth. The teeth are small, hard bones, thirty-two in number 

 in the adult, sixteen in each jaw ; their form is generally conical, the apex 

 in the alveoli. In each tooth we distinguish the crown, neck, and root. The 

 crown is external to the alveolus ; it has no periosteum, but is covered by a 

 firm, white, vitreous substance, named enamel. The neck is surrounded by 

 the gum, and the 7^oot is firmly held in the alveolus by a mode of connexion 

 called gomplwsis ; it is covered by the periosteum which lines the alveolus, 

 and which is reflected upon it from the point to the neck. The root or fang 

 of each tooth is perforated by a small hole for the nutrient nerve and ves- 

 sels. The teeth are divided into three classes, the incisores, the canini, and 

 the molares. 



The iiicisores are four in each jaw. The crown of these is sharp and 

 wedge-shaped, convex before, and thickly covered with enamel. The neck 

 is constricted, and the root is conical, but flattened on each side. Those 

 in the upper are stronger and larger than those in the lower jaw ; the 

 former are broader ; their edge is like a chisel, cut off posteriorly ; the latter 

 are more vertical, and bevelled off anteriorly ; they are not so sharp as 

 those in the upper jaw ; their roots are larger. The middle incisors in the 

 upper jaw are much larger than the lateral, but in the lower the lateral are 

 a little larger than the middle. 



The canine teeth, or cuspidati, are two in each jaw, or one on each side of 

 the lateral incisors. The crown is conical, a little blunt, convex before ; 

 their root is single, but very long, and larger than those of the incisors, 

 flattened at the side, and grooved. Their alveoli are often very prominent. 



The grinders, or molares, are twenty in number, ten in each jaw. The 

 crown of these is broad and irregular ; the roots are more or less divided. 

 The two first molars on each side in each jaw are called bicuspidati, and 

 are of an intermediate size between the canine and posterior molars. 

 They have only two tubercles on the crown, which is rather round. The 

 fangs in some are single, but usually double ; the lower are smaller than the 

 upper, and the tubercles on the crowns are not so deeply separated. The first 

 lower bicuspid frequently wants the inner tubercle, and resembles a canine. 

 The posterior grinders are the true molars or multicuspidati, three on each 

 side in each jaw. These are large ; the crown is somewhat square, has four, 

 and sometimes five tubercles ; the neck is thick and round ; the root has 

 three or four divisions, and each is perforated by a small hole. The 

 crowns of the lower are rather larger than those of the upper ; the latter 

 are vertical, but the former are inclined a little inwards. The fangs of the 

 lower are usually two, but very broad and strong, placed anteriorly and 

 posteriorly, often much curved, flattened before and behind, grooved and 

 often bifid. The first and second upper have usually three roots, one 

 internal, two external ; sometimes they have four. The first molar is gene- 

 rally the largest ; the last, or dens sapientia?, is the smallest ; its crown is 

 short, and has only three tubercles, two external and one internal. The 

 root, though often single, is grooved, and sometimes presents three partial 



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