OFFICES OF THE TEETH. 141 



teeth are very considerable ; and these diifer- 

 ences 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 prin- 

 cipally 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 grinding its harder portions. Occa- 

 sionally some particular teeth are much enlarged, 

 in order to serve as weapons of attack or of 

 defence ; for which purpose they extend beyond 

 the mouth, and are then generally denominated 

 tuski>; this we see exemplified in the Elephant ^ 

 the Narwhal, the Walrus, the Hippopotamus, 

 the Hoar, and the JBabiroussa. 



Four principal forms have been given to teeth, 

 which accordingly may be distinguished into 

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

 tuberculated 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 espe- 

 cially adapted. The conical teeth, Avhich are 



