DIGESTION DIAGRAM 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 lias 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 six 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 sometimes done ; without men- 

 tioning 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 



c 



