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NATURAL HISTORY. 



Class V PISCES. (Lat. Fishes.) 



Sub-class I PISCES OSSEL (Lat. bony fishes.) 



Order I.... ACANTHOPTERYGIL ( Gr. "AKavOog, a thorn; 



Trrepvyiov, a fin.) 



Sub-order I. DACTYLOPHORL (Gr. Aa/cri^o?, a finger; <j)pu, I bear.) 

 Family!.. . Triglidce. (Gr. Tpiyfa, a Mullet.) 



Cuculus (Lat. a Cuckoo), the Gurnard. 



As the FISHES live exclusively in the water, it is necessary 

 that their organs of respiration should be differently formed 

 from those of the animals breathing atmospheric air. Instead 

 of the purification of the blood being accomplished by the 

 contact of atmospheric air in the apparatus called lungs, that 

 office is performed by the water, which passes into the mouth 

 of the fish, and from thence out at the gill-covers, on its 

 way being strained through the singular structure called the 

 " gills." These gills are able to extract from the water suffi- 

 cient oxygen to purify the blood of the fish. If the oxygen 

 has already been extracted, the fish instantly dies. The same 

 effect is produced if the fish be so held as to prevent the 



