230 THE WONDERFUL HOUSE THAT JACK HAS 



by the blood, while their crowns are forced out as the 

 permanent teeth appear. From these facts we can see 

 that several of the second set of teeth may be in the 

 mouth before all of the first set have been removed. 

 So, if the latter are allowed to decay, the disease 

 may be given to the newly arrived second teeth and 

 great damage done them. Too great pains cannot be 

 taken with the sixth-year molars, for dentists find that 

 these are often the first to become diseased. Care- 

 lessness with them may cause much trouble in the 

 future. 



The regularity of the permanent teeth may also be 

 changed by losing the milk teeth before their natural 

 time. How may this happen? Let us imagine a 

 case. Because one of a child's canine teeth has been 

 allowed to become badly decayed, it is pulled. Now 

 the first bicuspids of the permanent set are pushing 

 their way through, but, since there is a vacant space 

 next to them, they crowd out in that direction, as 

 it is the path of least resistance. This tooth getting 

 out of position may cause others to change their 

 direction, and so the set of second teeth is much less 

 regular and beautiful than it might have been had the 

 milk teeth received proper care. 



Some little children, while teething, get comfort from 

 continually sucking a thumb or something similar. 

 Parents allow this because it helps to keep little ones 

 from being fretful. The practice should not be per- 

 mitted, for ; by pressing the teeth, it causes an ill- 



