142 



THE VITAL FUNCTIONS. 



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 Porpiis, the 

 {rfampus, 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 Porpus, shows the form of these simply 



prehensile teeth. The Cachalot has a similar 

 row of teeth, which are, however, confined to the 

 lower jaw. All these animals subsist upon fish, 

 and their teeth are therefore constnicted very 

 much on the model of those of fish ; while those 

 Cetacea, on the other hand, which are her- 

 bivorous, as the Manatus and the Diigoiig, or 

 Indian Walrus, have teeth very differently 

 formed. The tusks of animals must necessarily, 

 as respects their shape, be classed among the 

 <^onical teeth. 



