GENERAL REMARKS ON FISH. 53 



after being changed into arterial, by its contact with the air 

 in its passage through the gills, passes into the arterial trunk, 

 situated under the spine, and is dispersed by diminishing 

 blood-vessels, through the body, whence it returns by the 

 veins to the heart. 



As Fish breathe through the intervention of water alone, 

 and restore to their blood its arterial qualities, by means of 

 the oxygen which is suspended in the water, their blood is 

 naturally cold, often below the tempenature of the water they 

 inhabit. Immediately under the back bone is the air-bladder, 

 divided into two lobes or parts, which, by expansion or 

 compression, enables the fish to change its specific gravity, 

 and maintain any desired elevation in the water. In con- 

 aection with the gills, the air-bladder is homologous to the 

 lungs in land animals. 



There is no outward ear in fishes ; internally there is a 

 sack representing the vestibule, filled with gelatinous fluid. 

 By frequent experiments, Mr. Ronalds, the author of " The 

 Fly-Fisher's Entymology," ascertained that trout are not dis- 

 turbed by frequent and heavy discharges of firearms, if the 

 flash of the gun is concealed, and justly holds in derision, the 

 notion, that fish are frightened by persons talking on a 

 stream. They are more easily startled by the sudden jar of a 

 heavy tramp on an overhanging bank, or a thump on the 

 bottom of a boat ; the vibration from either of these causes, 

 acting on the nerves generally, rather than on the ear of the 

 fish. There are instances recorded, however, where fish have 

 been called by the ringing of a bell, or a familiar voice. 



There are no organs of voice in fish ; though some, — as the 

 Weakflsh, Croaker, Catfish, and Drum, make a croaking 

 noise when taken from the water, but these sounds are en- 

 tirely ventral. 



The sense of taste is necessarily deficient, or wholly want- 



