EARLY DESTRUCTION OF THE TEETH. 113 



extraneous matter, will be the first to be attacked 

 by the chemical agent. The molar teeth being of 

 this class, are therefore more liable to decay than 

 any of the other teeth. 



We have the reverse of this liability to decay in 

 the canine teeth and the incisors of the lower jaw ; 

 they are more uniform in their shape — their fangs 

 are thicker in proportion to their bodies — and they 

 do not present depressed necks and interstices as 

 the upper incisors do, and therefore they are less 

 liable to decay than the other teeth. To be con- 

 vinced of this fact, we have only to glance along 

 the shelves -on which are arranged the models 

 required in preparing artificial teeth, and we shall 

 find a large majority of them containing the lower 

 incisors when all the rest of the teeth have dis- 

 appeared. There is another reason to be assigned 

 for the lower incisors not being so liable to decay. 

 The saliva has a natural tendency to occupy the 

 lower part of the mouth, and these teeth are con- 

 stantly bathed in this fluid, which, by its property 

 of dissolving the particles of food, is in a great 

 degree calculated to remove them. The saliva itself 

 has no injurious efiect upon the teeth : it is the food 

 that mixes with it by which the mischief is occa- 

 sioned. The earthy matter contained in the saliva, 

 when allowed to be deposited upon the necks of the 

 teeth, takes possession of the fangs, forces the gums 



I from them, produces absorption of their periosteum 

 and alveolar processes; and from this cause they 



