DIGESTION DIAG RAM 1 . 17 



and four in the lower jaw ; eight in all. On each side of 

 the incisors, above and below, is another tooth, stronger and 

 more pointed, which has been compared to those of dogs, and 

 is only used when we wish to tear something ; these are the 

 canines, of which there are four. As to the molars, they serve 

 to grind like mills ; there are three on each side in each jaw 

 in children, and five in adults. 



The first teeth which make their appearance after birth are 

 the lower incisors. They show themselves first, and then all 

 the other teeth gradually appear, to the number of 24. 

 Towards the age of 6 years they come out, and 28 large ones 

 grow up in their places. The four last which complete the 

 number of 32, only appear much later, at an age when one 

 ought to be wiser ; they are called the wisdom teeth. These are 

 the last in each row. 



The teeth are formed of a very hard kind of bone which is 

 called ivory. They are divided into two portions : the root 

 which is buried in the gum ; and the crown, which is the visible 

 part. This is covered with a kind of brilliant varnish, called 

 enamel. In the centre of the tooth is a hole containing the 

 pulp ; or the flesh and nerves which sometimes cause us so 

 much suffering. The teeth, like the hair, should be kept very 

 clean, and brushed with soft brushes. One should always 

 avoid breaking too hard substances with the teeth, as is some- 

 times done. Without mentioning the risk of breaking a tooth, 

 it often happens that they crack without its being noticed, and 

 these teeth afterwards decay. 



When anyone opens his mouth very wide, and we look down 

 to the back, we see behind the tongue a " kind of curtain called 

 the uvula, (see diagram 2) which separates the mouth from the 

 throat. On each side, below the point where the uvula com- 

 mences, are the tonsils, (see diagram 2) which very often swell 

 in children, impeding their respiration, and causing them much 

 suffering. The part at the back of the uvula communicates 

 above with the openings of the nostrils ; and below with the 



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