ZOOLOGT. 163 



is kept up a constant supply and succession of food to the 

 various animals dependant on them for support. Immense as 

 the quantity is, that is consumed for food by Mankind, a 

 larger number are used for the purpose of extracting oil, or 

 for manure, of some kinds, Man has appropriated every part 

 to some use, as the Cod, whose flesh is eaten, and whose en- 

 trails are either applyed to the same purpose, or formed into a 

 kind of glue. Of some kinds, only the lirer is used to ex- 

 tract the oil, of others, only the skin, as that of the Dog- 

 fish, which is used for smoothing the surfaces of hard 

 wood, and various other substances, answering the purpose 

 of fine files. 



Fishes are separated into two divisions, Boni/ and Carti' 

 lagiTWus, either of which orders oflFers an easy gradation 

 from the last order in the class Amphibea, as the general ap- 

 pearance of the Snake, Eel, and Lamprey tribes clearly 

 shew. 



Bony fishes breath through Gills, covered or guarded by 

 bony plates, which are open on one side, and are dilatable at 

 pleasure, by means ol a row of bones situated on the under 

 part ; this division contains four orders, the characters of 

 which are taken from the absence, or situation of the 

 Ventral fins. 



Cartilaginous fishes have their muscles supported by car- 

 tilages, instead of bones, and they breathe through apertures 

 or holes, situated generally on the sides of the neck ] they ' 

 consist of only one order. 



M 2 



