ELEMENTARY PHYSIOLOGY 



Upper jaw 

 Lower jaw 



Upper jaw 

 Lower jaw 



M 

 3 



3 



M 

 } 



2) 



M 



il 



20 



TOOTH 



Dentine or 

 Ivory 



Enamel 



Cement 



Pulp Cavity 



STJMMAKY. 



i. The Milk Teeth. 

 MCI 



2 i 4 

 2 i 4 



The Permanent Teeth. 



B C I C 

 2141 

 2141 



Structure of a Tooth. 



Forms the greater portion of the tooth. 

 Harder than bone. 



Contains 72 per cent of mineral matter. 

 Hardest substance in the body. 

 Composed of very delicate fibres. 

 Contains only 2 or 3 per cent, of animal 



matter. 



Softer than dentine. 

 True bone. 



Contains lacunae and canaliculi. 

 Surrounds fangs. 

 Contains pulp. 

 Pulp consists of nerves and blood vessels, 



4. Mastication. 



Chiefly by the incisors. 



Motion of the jaw vertical. 



Chiefly by the molars. 



Aided by the muscles of the tongue, cheeks, and lips. 



Motion of the jaw varied. 



QUESTIONS ON LESSON XVI. 



1. Describe the general form and structure of a tooth. 



2. Name the different kinds of teeth, and point out the distinguishing 



characteristics of each. 



3. Why are the canine teeth so called ? In which of the lower animals do 



we find such teeth well developed ? 



4. Show in what way the form of a molar tooth is well adapted to the purpose 



for which it is used. How is the utility of the molar still further increased 

 by the movements of the lower jaw ? 



5. Describe the arrangement of the teeth in a child of about six years. 



6. Describe the arrangement of the different kinds of teeth in the jaws of an 



adult, giving also the number of each kind. 



7. Describe fully the structure of a tooth as shown in a section ; and give 



the general characters of the different materials of which it is composed. 



8. What do you suppose to be the usual cause of toothache ? 



9. How does the motion of the lower jaw of a dog, when feeding, differ from 



that of the cow ? 



10. Why do we masticate our food ? 



11. Is the motion of the jaw in eating a voluntary or an involuntary act ? 



Give reasons for your answer. 



Biting . 

 Chewing 



