OFFICES OF THE TEETH. 105 



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 principally 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. Occasionally, some 

 particular teeth are much enlarged, in order to serve as 

 weapons of attack or defence; for which purpose, they ex- 

 tend beyond the mouth, and are then generally denominated 

 tusks; this we see exemplified in the Elephant,\\\e, Narwhal, 

 the Walrus, the Hippopotamus, the Boar, and tire Babi- 

 roussa. 



Four principal forms have been given to teeth, which ac- 

 cordingly may be distinguished into the conical, the sharp- 

 edged, the flat and the tuberculated teeth; though we occa- 

 sionally 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 em- 

 ployed 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 the Cetacea, where 

 similar forms and arrangements of teeth prevail. All the 

 Dolphin tribe, such as the Porpus, the Grampus, and the 

 Dolphin, are furnished with a uniform row of conical teeth, 

 set round both jaws, in number amounting frequently to two 

 hundred. Fig. 273, which represents the jaws of the Por- 

 pus, shows the form of these simply prehensile teeth. 



The Cachalot has a similar row of teeth, which are, how- 

 ever, confined to the lower jaw. All these animals subsist 

 upon fish, and their teeth are therefore constructed very 

 much on the model of those offish; while those Cetacea, on 

 the other hand, which are herbivorous, as the Manatus and 



VOL. II. 14 



