104 STRUCTURE OF A TOOTH. 



10. The Pulp of a Tooth. If a tooth be broken open, a 

 cavity (c, Fig. 29) will be found inside it. It is named 

 the pulp-cavity, and during life is filled with a soft red 

 very sensitive core, full of blood and nerves, named the 

 pulp. At the tip of the fang, or of each fang, if the tooth 

 has more than one, is a small aperture through which 

 the nerves and blood enter. The pulp nourishes the 

 tooth; on account of the nerves in it, it gives rise to 

 great pain when exposed or inflamed. When a dentist 

 speaks of destroying or removing the " nerve" of a tooth, 

 he means the pulp. 



11. The Hard Parts of a Tooth (Fig. 29) are made of 

 three different materials. Surrounding the pulp-cavity 

 is dentine or ivory: an elephant's tusk is made of dentine. 

 Covering the ivory in the crown, is enamel, the tissue of 

 the body which contains least animal matter. It is so 

 hard that it will strike a spark with steel. Covering the 

 dentine in the fang, is what has been named the cement; 

 it is but a thin layer of bone under another name. The 

 dentine is harder than bone, though not so hard as 

 enamel. 



12. Hygiene of the Teeth. A great portion of the hard 

 parts of a tooth consists of a very hard kind of chalk, 

 and like chalk it is readily eaten away, or dissolved, by 

 sour or acid liquids. The mouth should therefore be 

 well washed after eating lemons or other sour things: 

 and acid medicines should be sucked through a glass 



10. What is the pulp of the tooth ? How do blood and nerves get 

 into the pulp ? Use of the pulp. Why called the nerve ? 



11. What is dentine? Enamel? Cement? How does dentine 

 compare with enamel ? 



12. What is the effect of acids on the teeth? What precautions are 

 therefore necessary for their preservation ? How may acids be made 

 in the mouth ? What is sajd of decay of the teeth ? 



