ON THE PRINCIPAL 



FORMS AND STRUCTURES OF THE TEETH. 



At the commencement of the Treatise on the Prin- 

 cipal Forms of the Skeleton, it was stated that " tooth," 

 like " bone," was the result of the combination of certain 

 earthy salts with a pre-existing cellular basis of animal 

 matter. The salts, as shown in a subjoined table, are 

 nearly the same as those in bone, but enter in a larger 

 proportion into the composition of tooth, and render it a 

 harder body. So composed, teeth are peculiar to the 

 back-boned (vertebrate) animals, and are attached to 

 parts of the mouth, commonly to the jaws. They pre- 

 sent many varieties as to number, size, form, structure, 

 position, and mode of attachment, but are principally 

 adapted for seizing, tearing, dividing, pounding, or grind- 

 ing the food. In some species they are modified to serve 

 as formidable weapons of offence and defence; in others, 

 as aids in locomotion, means of anchorage, instruments 

 for uprooting or cutting down trees, or for transport and 

 working of building materials. They are characteristic 

 of age and sex; and in man they have secondary rela- 

 tions subservient to beauty and to speech. 



Teeth are always intimately related to the food and 

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