236 NATURAL THEOLOGY. 



ness, and sharpness, and figure of the bills of birds. 

 Every thing about the animal mouth is mechanical. 

 The teeth of fish have their points turned back- 

 ward, like the teeth of a wool or cotton card. 

 The teeth of lobsters w^ork one against another, 

 like the sides of a pair of shears. In many insects, 

 the mouth is converted into a pump or sucker, 

 fitted at the end sometimes with a wimble, some- 

 times with a forceps ; by which double provision, 

 viz., of the tube and the penetrating form of the 

 point, the insect first bores through the integu- 

 ments of its prey, and then extracts the juices. 

 And what is most extraordinary of all, one sort of 

 mouth, as the occasion requires, shall be changed 

 into another sort. The caterpillar could not live 

 without teeth ; in several species the butterfly form- 

 ed from it could not use them. The old teeth, there- 

 fore, are cast off with the exuviae of the grub ; a 

 nev/ and totally different apparatus assumes their 

 place in the fly. Amid these novelties of form, we 

 sometimes forget that it is all the while the ani- 

 mal's mouth ; that, whether it be lips, or teeth, or 

 bill, or beak, or shears, or pump, it is the same 

 part diversified ; and it is also remarkable, that, 

 under all the varieties of configuration with which 

 we are acquainted, and which are very great, the 

 organs of taste and smelling are situated near each 

 other. 



III. To the mouth adjoins the gullet : in this 

 part also, comparative anatomy discovers a differ- 

 ence of structure adapted to the different necessi- 



