The Vancouver independent. (Vancouver, W.T. [Wash.]) 1875-1910, 1877-10-11
Fresh Water Fish.

1t is we'll known that fresh-water fish
cannot live in salt water, and vice versa,
and it has been supposed that the reason
existed in some poisonous effect which
the inappropriate water exerted. M.
Paul Bert has recently been investi-
eating this subject, and the conclusion is
that the death of the creature is not due
to any toxic action, but is simply phe-
nomenon of OsmOsis, or transmission of
fluids through the membranes. In order
to prove this, it is only necessary to
weigh the animal before and after the
experiment. A frog, for example,
plunged into sea water loses third its
weight. If only the foot of the frog be
introduced, the blood globules can be
seen to leave the vessels and distribute
themselves under the skin. If an animal
be taken, the skin of which is not entire
ly osmotic, the same phenomena occur in
the bronchial system.
tThere are certain fish, however, which
exist sometimes in salt sometimes in
fresh water, changing their habitation in
different periods of life or Of the year.
1t therefore, in view Of the above, be-
comes interesting to see how M. Bert ap-
plies his discovery to such apparent ex-
ceptions to the general rule. A fresh
water salmon, for instance, plunged alb
ruptly in sea-water, resists the effects
longer than other fresh fishes; but
he dies within five or six hours. This
shows, according to M. Bert, that the
fish never proceed suddenly from fresh
to saltwater, but enter brackish water
where the tide GIBBS and flows, and live
there sufficient time to habituate them
selves to the change. This accounts for
the frequent discovery of large numbers
of such migratory fish in the vicinity of
the mouths Of the rivers which they as
cend.
A fresh-water eel, plunged in salt-wa-
ter, does not seem to be affected, but in
investigating the peculiarities of this
species, NJ. Bert was led into a wrong
conclusion, which may be cited to show
how easy it is, often by pure accident, to
reach an erroneous determination in la
boratory experimenting. After having
himself placed several fresh-water eels,
he found, as already stated, that they re-
NAMED alive and unharmed. Wishing
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his assistant to introduce the fish, and re-
port results. To his surprise, the cells
then persistenly died after three or four
hours sojourn in salt water, and long
search failed to discover the reason why
it was that, when NJ. Bert placed them
in the tanks they lived, while, when the
assistant did so, they persisted. Finally,
NJ. Bert found that his assistant, doubt
less on account of the slipperiness of the
cells, lifted them with piece of cloth in
his hand. The cloth rubbed off little of
the natural slime of the animal, which
protected it from the saltwater. Osmo.
sis then occurred in the denuded portion,
and the eeleventually died.
The converse experiment of inserting
sea-tish in fresh water, produced analo-
gous results. The gills were the seat of
alterations, the same as those noted in
fresh water fish placed in saltwater. NJ.
Bert also observed sthat the life of the
sea fish could be prolonged by adding salt
to the fresh water, thus adding further
confirmation to his theory.