ON LATERAL TRESSURE. 173 



if ever, occur. The pressure of the tongue upon 

 the alveolus not only causes the plates of the 

 latter to be very thin, but also produces a more 

 even distribution of the enamel upon the surface 

 of the dentine. This renders the tooth less bold 

 in outline, more uniformly coated with enamel, 

 and causes the edges of the several plates to 

 meet and be thoroughly united. 



It is not improbable but that the pressure thus 

 exerted upon the crown of the tooth during the 

 period of its being formed within its cell, has 

 much to do with the first permanent molar being 

 so commonly incapable of resisting decay. When 

 within the cell, its much greater thickness than 

 the temporary molars causes the alveolus to 

 form a considerable projection inwards, and thus 

 places it more in the way of the contiguous parts. 

 This is not the case with the second molar, 

 because the increased width of the alveolus at the 

 first molar forms a protecting screen. That the 

 latter condition constitutes by very far the largest 

 proportion of the causes for the teeth being re- 

 moved, is universally admitted, and by these teeth 

 mostly decaying in many places simultaneously, 

 there can be little doubt but that a large portion, or 

 perhaps the whole, of the crown of the tooth has 

 been subject to some detrimental influence in the 

 early stage of its being formed ; and although it 

 may be possible that the effect may arise constitu- 

 tionally, or from irritation, or some other causes 



