A natural question remains:  how could they count out Avogadro’s number, when molecules are so extra-ordinarily much smaller than grains of sand?  The answer to this question begins with the leg of a frog!

Suppose you were dissecting a frog’s leg.  It had long been severed from the rest of the frog and kept in a preservative much like formaldehyde.  This was not like the proverbial chicken with its head cut off.  This frog’s leg had no memory of having been a part of a frog.  All of a sudden it starts to twitch!  What would you think?  What would you do?

I think I would have looked around to see if someone was playing a trick on me, but that’s not what Luigi Galvani did back in 1798 when this happened to him.

Dr. Galvani was interested in how nerves control muscles.  That’s why he was dissecting frogs’ legs.  They are a good animal model for this issue.  The nerves in a frog’s leg are large and easy to get at.  When the leg began to twitch, Galvani began to systematically ‘test’ things.  If a window was open, he closed it.  If a candle was lit, he blew it out.  He kept trying things to see what might be causing the leg to do its dance.  In time he discovered two things.  The leg stopped twitching if he raised either the scalpel or the scissors, and began again when he laid them down.

What an extra-ordinary discovery!  Here was dead flesh brought to life by two simple instruments, two knife edges.  In time Galvani and others worked out that there was a third necessary ingredient, acid.  Two different metals and an acid interact to generate electricity, current electricity…what is still sometimes called galvanic electricity.  Until then, electricity was only known in its static form as a shock delivered on a cold winter’s day as you reached to shake someone’s hand or to open a door; or perhaps if you tied a key to the string of a kite.   But this was different.  Here electricity would flow continuously, as long as the metals and acid were in contact.  Galvani’s frog’s leg was a battery!

Immediately, word went out that Galvani had discovered the mystery of life, the vital force that animated tissue.  And not long afterwards Mary Shelley wrote the classic novel, Dr. Frankenstein, where the doctor’s monster is human flesh, long dead, brought to life by a bolt of electricity.  This is a fascinating moment in the history of how we have come to understand the nature of life, but our interests take us in a different direction.  We want to follow the trail of the battery and the chemical researches it engendered.