X. 



THE ORGANS OF DIGESTION. THE TEETH 

 AND THE TONGUE. 



A. The Parts of a Tooth. 



Material. A human incisor tooth. 



Specimens of the different kinds of human teeth may 

 be obtained of a dentist. 



Study an incisor tooth with reference to the different 

 parts. 



Observe : 



a. The crown is the upper part seen in the mouth. 



b. The root, or fang, is the part embedded in the jaw- 

 bone. 



c. The neck is a narrow part between the crown and 

 the root, embraced by the edge of the gum. 



d. The hole is at the tip of the root. What is its use ? 



e. Sketch a side view. 



B. The Structure of a Tooth. 



Material. A slide showing a longitudinal section of a human 

 incisor tooth. 



Apparatus. A magnifying glass. A compound microscope. 



1. Study with a magnifying glass a prepared microscopical 

 slide of a longitudinal section of an incisor tooth, 

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