DIGESTION OF FOOD. 



\ 



289 



The latter is filled by the tooth-pulp, which consists of a 

 delicate connective tissue supporting blood-vessels and nerves 

 which ramify in it after entering by the openings in the fang 

 of the tooth. From the pulp pi'otoplasmic fibers extend into 

 the dentine tubules. 



The crusta petrosa is very similar to bone, but is usually i 

 without Haversian canals, and, like bone, is covered with peri- / 

 osteum. 



Fio. 241.— The teeth of the ox (Chanveau). 1, upper jaw, with a. friction surface and 

 i, external surface; 2, lower jaw, with o, dental tables, and S, external face. 



Teeth are simple and compound. In the former (carnivora) 

 the entire crown is covered with enamel ; in the latter, owing 

 19 



