HUMAN PHYSIOLOGY 



CENTRAL INCISORS 



CHAP. 



LATERAL INCISOR 



CUSPID OR CANINE 

 FIRST BICUSPID 

 SECOND BICUSPID 



OR WISDOM 



FIG. 38. Upper jaw, showing permanent teeth in place. (From Hopkins' 

 " Care of the Teeth." D. Appleton & Co.) 



69. Structure of the Teeth. The external appear- 

 ance shows three parts : the crown, or the visible portion 

 projecting beyond the gum ; the root, or the portion 

 hidden in the gum ; and the neck, or narrow border 

 between the crown and the root. 



A tooth sawed through the middle from crown to 

 root shows that it is made of four different things. The 

 main part of the framework of a tooth is a bonelike 

 substance called dentine. The dentine of the root is 

 covered with cement and that of the crown with a 

 very hard, highly polished substance, called enamel. 

 Enamel is the hardest substance in the body ; it serves 

 to protect the tooth. There are no blood vessels and 

 nerves in the enamel, and for tJiat reason a tootJi cannot 



