170 ANIMAL FORMS 
is forced through the gills, with all their delicate filaments, 
and now, laden with oxygen and nutritious substances al- 
ready absorbed from the coats of the digestive tract, it 
opt kd 
ih ae 
nacah | ae) WY 
if 
Nw 
Fie. 106.—Dissection of a bony fish, the trout (Salmo). a.bl., air-bladder ; an., anal 
opening ; au., auricle; gi.st., gills; gul., esophagus; in¢., intestine; kd., kidney ; 
7r., liver; l.ov., ovary; opt.l., brain ; py.c., pyloric ‘ceeca ; sp.c., spinal cord; spl., 
spleen ; sf, stomach ; v., ventricle. 
travels on to all parts of the body, continually unloading 
its cargo in needy districts and. waste matters in the kid- 
neys before returning once more to the heart. 
163. The senses of fishes——The habits of fishes indicate 
that they know considerable of what is going on in the 
outside world, and their well-developed sense-organs show 
the degree of their sensitiveness. A share of this informa- 
tion comes through the sense of touch, which is distributed 
all over the surface of the body, chiefly in the more ex- 
posed regions sometimes especially provided with fleshy 
feelers, like those on the chin of the catfish. 
The sense of smell appears to be fairly developed, as is 
that of hearing; but there is no evidence of a sense of taste. 
A few fishes chew their food, and may possibly taste it, but 
there are others that swallow it whole, and in all there are 
relatively a few nerves going to the tongue or floor of the 
mouth. 
