264 RESPIRATION, SMELL, AND TASTE OF FISHES. 



the water in whicli they live, owing to the great quantity 

 of fat they contani, so that very little effort is required to 

 keep them at any given height, and their ascent or descent 

 in the water. 



The circulation of blood is peculiar. There is but a 

 single heart in fishes, that is, a heart consisting of only two 

 cavities; and these correspond not to the left heart of mam- 

 mals or birds, but to their right or pulmonic heart. 



Respiration is carried on by means of the gills, Avhich 

 take the place of lung?, and consist of a large number of 

 blood vessels, placed near the forward extremity of the ani- 

 mal, and protected by a bony case or covering, often 

 defended by strong spines. The gills are placed in imme- 

 diate communication with the heart. Water, which is 

 impregnated with atmospheric air, entering at the mouth, is 

 forced out again by the apertures at each side of the neck, 

 and thus maintains almost a constant stream or rush through 

 them, entering and again expelled at intervals. When 

 fishes are taken from the water, the delicate thready 

 structure of tlie gills immediately collapses; when exposed 

 to the air a kind of suffocation ensues, and death is the 

 result. This is the general principle of respiration in fishes, 

 but in some cases the structure varies. 



The smell of fishes in some species is remarkable: 

 they scent their prey at a great distance, and the very per- 

 fection of this function is often fatal to them. Some fishes 

 are so allured by scents, that by smearing the hand over 

 with them, and immersing it in water, fishes (not sharks, 

 let us hope) will often flock toward the fingers, and may 

 easily be taken. Fishermen have the habit of making their 

 bait more attractive by steeping it in some strong-smelling 

 ingredient. On the American shores, tlie fishermen use 

 putrid or damaged fish as bait for mackerel. They are 

 thrown in a box hopper, in which a cylinder studded with 

 knives is made to revolve by a crank. This is called the 



