DIGESTION. THE TEETH. 



24. In man, and those animals which, in their organization, 

 resemble us most, the two jaws are situated one above the other ; 

 the upper jaw is fixed immovably to the cranium; but the lower 

 jaw is only attached to it, at its posterior part, and is there held 

 on each side by a sort of hinge or joint, which permits it to be 

 separated from and approached to the upper jaw. ; . 



Fig. 14. 25. The muscles which serve to bring 



the jaws together, and which, conse- 

 quently, act most during mastication, 

 are placed on each side of the head, in 

 front of the ear (Fig 14.), and when we 

 press the teeth together, we can feel that 

 they contract. 



26. In most mammalia the edges of 

 the ja.ws are armed with teeth. 



27. The teeth are small hodies of 

 great hardness, which resemble bone 

 re/v much; they ai e planted in holes, 



hollowed info the jaws, which holes are named alueuli. 



28. The fibrous pads 

 which cover the edge of 

 the jaws, and which are 

 called (/inns, serve, as 

 well as the alveoli, to fix 

 the teeth solidly in the po- 

 sition which they occupy. 



29. Generally, each 

 tooth is divided into two 

 parts; one is situated with- 

 out, and called the crow*, 



the other, buried in the alveolus (/*'*#. 



15.), and terminated by 



Explanation of Pip?. 14. The head seen in profile, to show the parotid 

 gland, (gp.} and the chief levatur, or elevating muscles of the lower jaw 

 namely, the temporal (rnf.) ami maseter muscles, (rn,w.) 



Explanation of Fig. 15 Lower jaw of a man opened to show the man- 



ner in which the roots of the teeih (r ) penetrate its Ruhstance (</.) A. the 



superior edge left en! ire, t. incisor teeth, c canine teeth, fin. false molar 



teeth, gm. great molar teeth, ed. condyle of the jaw which enters into its 



"ticulation with the rianium. 



24. What is the situation of the jiws? Are hot h jaws equally moveable ? 

 2.). Where are those muscles pliced which rnovc the jaws? 

 2(5. Have all animals got teeth? 



27. What are the teeth ? What are the alveoli f 



28. What are the gums? 



29. Into what parts Is a toolh divided ? What is the neck of a tooth T 



