110 EARLY DESTRUCTION OF THE TEETH. 



We find, however, that a complete union of the 

 isolated portions does not take place ; when at last 

 the membrane ceases to furnish a farther supply ; 

 and the result is, that when the tooth makes its 

 appearance, fissures are found in the enamel, which 

 often extend to the surface of the bone. 



The enamel of a tooth, as we all know, consists 

 principally of the phosphate of lime combined with 

 a small portion of animal matter. It is a more 

 dense and rocky structure than the bone of the 

 tooth, because the bone contains a smaller portion 

 of lime, and a larger portion of animal matter. 

 Between these substances — that is, the lime and 

 the animal matter — there exists a strong power of 

 affinity which combines them into a solid body, 

 and holds them together in rocky union, whereby 

 the structure of the tooth is formed and maintained. 

 But this power of combination may be destroyed 

 by chemical agency : for by the application of a 

 strong acid to the tooth, the part acted upon loses 

 the power of affinity, and crumbles into its original 

 particles. This is what has been termed decay of 

 the teeth. Now, the term is applicable in the case 

 of organized bodies which depend upon foreign 

 aid for their existence, nourishment, and growth, 

 so that if this nourishment be withheld, death 

 and decay must be the result : but the term is 

 not so applicable to the destruction of inorganic 

 bodies. 



The materials which compose the structure of 



