Electrochemical Basis of Cell Function

The cell's integrity is constantly threatened - its macromolecules exert an osmotic force that tends to cause the cell to swell and burst. Countering this danger are the pumps and channels of the cell that generate electrical fields and chemical gradients. This site's OsmoLab is designed to explain how this is possible. 

Once the cell has tamed the osmotic forces of its macromolecule, it was free to use these tools for a wide variety of other purposes.  For instance, this 19^th century lab demonstration (illustrated above) employed three freshly severed oxen heads and a frog sartorius muscle. Connecting this all together, muscle-to-tongue₁, brain₁-to-tongue₂ brain₂-to tongue₃ and finally tongue₃ to a stimulating electrode, would cause the muscle to twitch when touched by the stimulating electrode. In this case, the muscle is electrically excitable via an action potential and the tongue's epithelium transports fluid by a battery-like mechanism. Three batteries in series generated sufficient current to trigger the muscle's action potential!