One of the things I really liked about Nelson's chapter on Nerve Impulses was the figure below. (Left click to make it larger.)
In the caption he says, "Perhaps the most remarkable experiment described in this book."
Why is this data so important and profound?
I would say that it is another defeat for "vitalism" and victory for both reductionism and emergence.
It is a victory for reductionism because it shows how a specific biological phenomena (nerve impulses) can be essentially reduced to a purely physical effect.
It is a victory for emergence because it shows how the shape and speed of the voltage pulses is universal and independent of many of the biological and biochemical details.
The right panel shows the time dependence of the voltage across the membrane of a "live" axon (a single nerve) cell.
In contrast, in the left panel the contents of the cell (a complex biochemical mix!) have been removed and replaced with just a solution containing the same amount of potassium ions as the "live" cell. [But the cell membrane and its ion channels are intact].
In passing, I mention that this does not mean that consciousness is "just" electrical activity. But that is another story....