The Russellville Democrat., 1877-06-21
Why Fresh Water Fish Cannot live in
 Salt Water.

It is well known that fresh water fish cannot live in salt water, and cice versa; ; and it has been supposed that the reason exists in some poisonous effect which the inappropriate water exerted. Mir. Paul Bert has recently been Investigating this subject, and his conclusion is that the breath of the creature is not due to any toxic action, but is simply a phe- nomt non 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 in sea water loses one. third its weight. Ifonly 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 ami nal be taken, the skin of which is not entirely osmotic, the same phenomena occur in the bronchial system.
 There are certain fish, however, which exist sometimes in salt, sometimes in fresh water, changing their habitat in different periods of life or of the year. It, therefore, in view of the above, be- comes interesting to see how M. Bert ap- plies his discovery to such apparent ex- captions to the general rule. A fresh water salmon, for instance. plunged ab- ruptly in sea water, resists the effects longer than other fresh water fishes but he dies within five or six hours. This shows, according to M. Bert, that the fish never proceed suddenly from fresh to salt water, but enter brackish water where the tide ebbs and flows. and live there a sufficient time to habituate them- selves to the change. This accounts for the frequent discovery of large numbers of the migratory fish in the vicinity of mouths of rivers which they ascend.
 A fresh water eel, plunged in salt water does not seem to be affected. But Investigating the peculiarities of this species M. Bert was led to a wrong con clusion, which may be cited to show how easy it is, often by pure accident, to reach an erroneous determination in lab oratory experimenting. Alter having himself placed several fresh water cells in salt water, he found as already stated, that they remained alive and unharmed. Wishing to continue the experiments, he directed his assistant to introduce the fish and report results. To his surprise the eels then consistently died after a three or four hours sojourn in the salt water, and long search failed to discover the reason why it was that when M. Bert placed them in the tanks they lived, while when the assistant did so they per ished. Finally, NJ. Bert found that the assistant, doubtless on account of the slip7eriness of the eels, lifted them with piece of cloth in his hand. The cloth rubbed of little of the original slime of the animal, which protected it from the salt water. Osmosis then occurred in the denuded portion, and the eel eventually died.
 The converse experiment, of inserting sea fish in fresh water, produced analo- gus results. The gills were the seat of alterations, the same as those noted in fresh water fish placed in salt water: M. Bert also observed that the life of the sea fish could be prolonged by adding salt to the fresh water, thus adding further con- frmation to his theory.-'Scientifc Amer ie0u