240 UNCONSCIOUS NERVOUS OPERATIONS 



when a child is ten or eleven years old, cannot be renewed 

 or improved after that time. It is therefore of the utmost 

 importance that young children should be fed upon food 

 which will build up perfect teeth. Milk should be largely 

 relied upon for the first three years, the diet to be varied 

 during the third and after years in accordance with sug- 

 gestions given in the chapter on Food. Great care should 

 be taken to guard children against attacks of what are 

 known as " infantile diseases," measles, whooping cough, 

 etc., which sometimes suddenly arrest or disturb the gen- 

 eral nutrition, and especially that of the teeth, so that the 

 enamel becomes rough and irregular, and the teeth are 

 exposed to early decay. Another point should receive 

 special attention. It is observed that young children 

 who live a life of excessive nervous activity, with over- 

 stimulation of the brain, are particularly liable to defect- 

 ive development of the enamel of the teeth. This is one 

 among many reasons which make imperative a quiet, regu- 

 lar life for children, without excitement and without 

 undue mental activity. 



347. But even perfect teeth may be injured by certain 

 bacteria, which multiply in the decaying particles of food 

 allowed to remain in the mouth. These minute organisms 

 form a corrosive acid which destroys the enamel and breaks 

 down the tooth substance. If the teeth are perfect and 

 are always kept perfectly clean, they will not decay. 

 They should be thoroughly brushed the upper teeth 

 downward, the lower ones upward after each meal, and 

 a thread of soft untwisted silk floss or fine strips of rubber 

 should be drawn back and forth between the teeth to cleanse 

 those parts which a brush cannot reach. In brushing the 

 teeth a powder or liquid should be used which contains 

 some safe germicide, which is a substance destructive to 



