126 THE VITAL FUNCTIONS. 



among the teeth are very considerable ; and these 

 differences have, accordingly, been the object of 

 much careful study. To the physiologist they 

 present views of still higher interest, by exhibiting 

 most striking evidences of the provident care with 

 which every part of the organization of animals 

 has been constructed in exact reference to their 

 respective wants and destinations. 



The purposes answered by the teeth are princi- 

 pally those of seizing and detaining whatever is 

 introduced into the mouth, of cutting it asunder, 

 and dividing it into smaller pieces, of loosening its 

 fibrous structure, and of breaking down and grind- 

 ing its harder portions. Occasionally some par- 

 ticular teeth are much enlarged, in order to serve 

 as weapons of attack or of defence ; for which pur- 

 pose they extend beyond the mouth, and are then 

 generally denominated tusks; this we see exempli- 

 fied in the Elepliant, the Narivhal, the Walrus, the 

 Hippopotamus, the Boar, and the Sahiroussa. 



Four principal forms have been given to teeth, 

 which accordingly may be distinguished into the 

 conical, the sharp-edged, the flat, and the tubercu- 

 lated teeth ; though we occasionally find a few 

 intermediate modifications of these forms. It is 

 easy to infer the particular functions of each class 

 of teeth, from the obvious mechanical actions to 

 which, by their form, they are especially adapted. 

 The conical teeth, which are generally also sharp- 

 pointed, are principally employed in seizing, 

 piercing, and holding objects: such are the offices 

 which they perform in the Crocodile, and other 

 Saurian reptiles, where all the teeth are of this 

 structure ; and such are also their uses in most of 



