8 SALMON. 



abridged from Cuvier's great work on the animal 

 kingdom, I shall only add, that fishes are oviparous 

 animals, with a double circulation, their respiration 

 being, as already stated, through the medium of their 

 branchiae, or gills, the filaments of which receive the 

 oxygen of the air contained in the water, on its passage 

 through them, which receives the carbon in return, as 

 in the lungs of an air-breathing animal. The gills of 

 a fish do not decompose water so as to derive oxygen 

 from it, but merely separate the oxygen from the 

 atmospheric air contained in the water. Hence, if 

 water is deprived of this air, or is impregnated with de- 

 leterious gases, fish cannot live in it. As little can they 

 bear the return of water entering at the gill-openings, 

 and escaping by the mouth; for if a fish is held so that 

 the water is made to pass in this direction, it is as 

 speedily drowned as if it were an air-breathing animal. 



SECT. I. THE SALMON. 

 Salmo Salar. 



THIS is justly regarded as the king of fresh-water fish, 

 it being placed amongst such fish, because it leaves the 

 sea to deposit its spawn in the rivers. Having 

 done this; it returns to the briny deep, dividing 

 its time pretty well between the salt water and the 



