FISHES. 
29 
exists among the races, and the indefatigable 
assaults committed by man upon them, it is pro- 
bable that the actual average of life among Fishes 
is of comparatively short duration. 
Tenacity of life must be distinguished from 
its durability. In this property much difference 
is found amongst fishes. Mr. Yarrell observes 
that those species which swim near the surface 
of the water, have a high standard of respiration, 
a low degree of muscular irritability, great ne- 
cessity for oxygen, die soon — almost immediately 
on being taken out of the water — and have flesh 
prone to rapid decomposition ; of these. Mackerel, 
Salmon, Trout, and Herrings are examples. On 
the contrary, those that live near the bottom 
have a low standard of respiration, a high degree 
of muscular irritability, and less necessity for 
oxygen : these sustain life long after they are 
taken out of the water, and their flesh remains 
good for several days: Carp, Tench, Eels, the 
different sorts of Skate, and all the Flat-fishes 
are examples of this class. Some species, as 
the Eels and the Ophiocephali, continue to ex- 
hibit vigorous tokens of life, under inflictions 
that would be fatal to most other animals ; the 
removal of the skin, and even the division of the 
body into pieces, not immediately producing 
death. 
The power of sustaining extremes of tempera- 
ture, found in this Class of animals, may perhaps 
be considered an indication of their low place 
in the scale of organization. Broussonet found, 
by experiments, that several species of fresh- 
water Fishes lived many days in water so hot 
that the hand could not be held in it a single 
