The Structure of Game Fishes 3 
The large bone (28) is the cover, or door, to the 
gill chamber, which opens and closes convulsively 
when a fish is landed. The fish smells but does 
not breathe by its nostrils, the nasal aperture 
being shown at (15). 
In the skeleton the arrangement and use of the 
limbs, or fins, is readily seen. The top or dorsal 
fins (75) are balancers, upper centre-boards, 
capable in some fishes of a decided screwlike 
‘movement, enabling them to move. It also is an 
expressive organ, erect when the fish is excited, 
low or folded at other times, and incapable of 
movement in certain forms. In the tuna it fits 
into a scabbard, or notch. The tail, caudal fin 
(71), is the most useful locomotive organ, con- 
trolled by powerful muscles and lashed about by 
the entire sweep of the body; it is readily seen 
that by it the salmon makes its tremendous leaps 
and the tuna literally whirls itself into the air, 
nearly all fishes using it as a screw. The peculiar 
motions are readily observed in a soft-tailed fish, 
like the perch, in confinement. 
Directly below the second dorsal fin, near the 
tail, is the anal fin (86) and its bones, held in 
place by spines (79), which are placed firmly in 
the muscular tissue. It is these interspinous and 
