THE TEETH AND MASTICATION 89 



but is penetrated by a multitude of very delicate tubes which 

 communicate with the cavity of the tooth. 



This cavity is called the pulp-cavity. It contains a very soft 

 substance the pulp. This consists of a mass of minute blood- 

 vessels and nerves which enter through an opening at the point of 

 each fang. 



The dentine which forms the crown of the tooth is covered 

 with a substance called the enamel. It is the hardest substance 

 in the body, and contains only two or three per cent, of animal 



Fig. 87. Longitudinal Section of a Molar Tooth. 

 k, crown ; , neck ;f, fangs ; e, enamel ; d, dentine ; c, cement ; p, pulp cavity. 



matter. When examined under a high magnifying power, the 

 enamel is seen to consist of exceedingly fine hexagonal fibres. 



The root of each tooth is surrounded by a substance called 

 the cement. This substance is softer than the dentine, and in 

 structure resembles bone it contains lacuna and canaliculi, but 

 no Haversian canals. 



The use of the teeth is to masticate the food, that is, to reduce 

 it to such a finely divided state that it may be readily acted on by 

 the various digestive fluids. It has already been noticed that the 

 different kinds of teeth are adapted for different modes of action ; 



