114 



THE VITAL FUNCTIONS. 



rn a growing state, the fangs are not )-et added, but they are, 

 at one part, beginning to be formed. The same tooth, in its 



'^<'^^ 



usual state, as worn by mastication, gives us a natural and 

 horizontal section of its interior structure, in which the plates 

 of white enamel are seen forming waved ridges. These con- 

 stitute, in the Asiatic Elephant, a series of narrow transverse 

 bands, (Fig. 2S3,) and in tlie African Elephant, a series of 

 loy.enge-shapcd lines, (Fig. 2S2,) having the ivory on their 

 interior, and the yellow crusta petrosa on their outer sides; 

 which latter substance also composes the whole circumfe- 

 rence of the section. 



§ 4. Formation and Development of the Teeth. 



Few processes in animal development are more remarka- 

 ble than those which arc employed to form the teeth; for 

 they are, by no means, the same as those by which ordina- 

 ry bone is constructed; and being commenced at a very ear- 

 ly period, they aftbrd a signal instance of Nature's provident 

 anticipation of the futiu'e necessities of the animal. Tiic 

 teeth, being the hardest parts of the body, require a peculiar 



