HOW FISHES BREATHE. 
347 
month being cut off — is forcibly driven out backwards, again 
to join the waters of river or sea, by the speedy folding up of 
the branchiostegal membrane, and by the shutting of the 
opercular doors upon sills formed behind them by the bones 
which carry the pectoral fins. 
In the operation of “ drowning ” a hooked fish, which is 
familiar to every angler, the opercula of the fish which is being 
towed down stream must be either pressed forcibly against the 
sides of the head or be forced widely aside, the result of 
which is to embarrass, and, ultimately, put an end to, respira- 
tion ; in the first case, by the hindrance to the proper dis- 
tension of the branchial chambers, and the consequent absence 
of a vacuum — if such an expression can be used — which shall 
be filled by the water taken in at the mouth, not to mention 
the want of room for the play of the gills ; in the second 
instance, by the retention of the water, now useless for breath- 
ing purposes, in the gill-chambers, since the doors which ought 
to force and shut it out can no longer do their work. 
The size of the outlets of the branchial chambers seems to 
bear an inverse ratio to the length of time during which a fish 
is able to breathe when taken out of the water ; for in those 
fishes, such as the mackerel and herring, which die very soon 
after removal from the water, these openings are relatively 
large ; while in the eel tribe, which not only can exist for some 
time after being landed nolens volens , but sometimes make “ on 
their own hook ” considerable overland excursions, the outlet 
from the gill-chamber “ is a small vertical fissure, situated at 
some distance behind the gills ; the branchial cavity is there- 
fore proportionately elongated, and the escape of fluid from it 
is consequently impeded.” 
The Anabas ( Perea scandens ), which, on the authority of a 
Danish lieutenant,* is yet believed by many to make somewhat 
purposeless expeditions up the trunks of palm-trees, can, un- 
doubtedly, whether it climb or not, exist for a long time out of 
water. Dr. Hamilton writes thus of this fish : “ Of all that I 
know, the cobojius is the fish most tenacious of life in the air ; 
and I have known boatmen to keep them for five or six days in 
an earthen pot without water, and daily to use what they 
wanted, finding the fish as lively and fresh as when caught. In fact 
the Calcutta market is chiefly supplied from extensive marshes in 
the Yasor district, and about 150 miles distant. From thence 
boat-loads are brought, kept alive without water until sold.”f 
This fish, together with certain others, e.g. the “ Grourami ” 
( Osjohromenus olfax) of the Isl e-de-France, has, as Cuvier has 
* Daldorff. (See Trans. Linn. Soc., vol. iii. p. 62.) 
t Fishes of the Ganges , vol. i. p. 99. 
* 
