Xll INTRODUCTION. 



" The teeth are quite constant in the same type, are 

 generally appreciably modified according to family, are 

 the most readily preserved in a fossil state, and are in 

 direct relation with the economy of the animal. Hence 

 they furnish the best indications of the relations of 

 the animal to which they belonged, especially in cases 

 where the type was not very different from an existing 

 one. In the case of the older and more aberrant types, 

 however, the indications furnished by the dentition 

 should be accepted with great caution." 



In the Introduction to his " Odontography " Prof. 

 Owen gives, besides his own and other men's views, a 

 history "of the leading steps to the present knowl- 

 edge" of dental science (that is, up to 1844), of which 

 the following are extracts : 



" As regards the teeth, the principle of chief import 

 to the physiologist arises out of the fact, which has 

 been established by microscopic investigations, that the 

 earthy particles of dentine are not confusedly blended 

 with the animal basis, and the substance arranged in 

 superimposed layers, but that these particles are built 

 up with the animal basis as a cement, in the form of 

 tubes or hollow columns, in the predetermined arrange- 

 ment of which there may be discerned the same rela- 

 tion to the acquisition of strength and power of resist- 

 ance in the due direction, as in the disposition of the 

 columns and beams of a work of human architecture. 



" Whoever attentively observes a polished section or 

 a fractured surface of a human tooth may learn, even 

 with the naked eye, that the silky and iridescent luster 

 reflected from it in certain directions is due to the 

 presence of a fine fibrous structure. 



