What's in your wallet?

People carry money about, save it, and spend it, but often know almost nothing about it.

I teach biology at a college here in Maine. Sometimes the lessons proceed in unanticipated directions.

This is exactly what happened recently during a laboratory exercise. The topic was taxonomy – the classification of living things. Using American money as an example of how things are logically ordered, I asked my students to write a classification scheme that would divide the various denominations into groups with related features. "Think of characteristics shared by different coins and bills," I instructed. "For example, the coins have a Latin motto."

What Latin motto? Most had never heard of a Latin motto. So I told them to take out a coin and look for something that wasn't in English. They found it, but it was as if they had never seen it before. "E Pluribus Unum." Out of many, one. A beautiful motto. One of the best. It certainly has more gravity than Aruba's motto, "One Happy Island."

My students' lack of knowledge about the national motto piqued my curiosity. I told them to put their money away. Then I took out a handful of change and a few bills. "Who's on the penny?" I asked. Most of them knew that it was Lincoln.

Then I asked the next logical question: What's on the back of the penny? Two people said, "A house." Not one of the 20 named the Lincoln Memorial.

All right, then. On to the nickel. Who's the guy on the nickel? Two people got Jefferson right, but none of them knew what was on the back of this coin: Monticello. My biology laboratory was quickly becoming a lesson in numismatics, US history, and literacy.

"Don't you folks ever read your money?" I chided.

One replied (and I should have seen this coming), "No, we just spend it!"

There it was, then. My students took money completely for granted. They carried it about, saved it, spent it, lost it, sought it, but knew almost nothing about it. As an erstwhile coin collector, I was happy to share my expertise. "Why do some coins have grooved edges?" I asked. What I got in return was the obvious answer: so blind people can tell them apart. While this is certainly one of its benefits, it wasn't the original impetus for the feature. Grooved, or reeded, coins were introduced as a guard against people shaving the edges of gold and silver pieces and then passing the coins back into circulation.

From there, we went on to a conversation about hairdos. Why did George Washington wear a wig? A few shrugs from my audience gave way to one suggestion that it was "just the style" back then. Well, this is partially correct, but it had more to do with hygiene. Colonials did not believe in frequent bathing, for fear it would wash away the body's essential oils. The result was lice. In many men, this unseemly condition was compounded by natural hair loss, so it was easier to shave one's head and care for a wig, which was often made from the hair of horses or goats.

At this point, my students were leaning forward, their eyes bright. It was clear that the idea of a president wearing a wig with a ponytail and bow – a real hepcat – was far more interesting than a discussion of the taxonomic position of the blowfish.

We moved on to paper money. "Who's on the dollar?" I asked, as if positing the opening question of "Who Wants to be a Millionaire?" Washington was a no-brainer for them. Lincoln on the five-spot was also an easy one, Hamilton on the $10 stumped a few, Jackson on the $20 a few more, and only one person placed Grant on the $50. None of them knew that Hamilton was the only one of these men who was never president.

How about the $100 bill? Interestingly, most knew Ben Franklin. But I left them in the dust when I asked them about the now-extinct $500, $1,000, and $5,000 notes (William McKinley, Grover Cleveland, James Madison). And then, as a sort of coup de grâce, I brought out the big gun: "Who," I asked, "is on the $100,000 bill?"

This one unsettled them. "There's no such thing!" one bold male exclaimed, to cheers of approbation for his taking a stand against the suggestion that such a large note could possibly exist.

"At one time there was," I said, calming the crowd. "And the portrait was of a First World War-era president."

You mean, there was a war before the Second World War? Well, yes. But none of my students knew the name of the chief executive at the time (Woodrow Wilson).

Our excursion through US currency and its lore was time well spent because the unspoken message it conveyed was that in science, it's important to be good observers, to look closely, and to ask questions. As we ended the topic, one student asked why a person would want to own a $100,000 bill.

"Actually, it's illegal for a private citizen to own one," I said. "They were used only for transactions between Federal Reserve banks."

"What if I find one lying around?" asked the class wisecracker, generating a few supportive laughs.

"That's easy," I said. "Give it to me. I'll take care of it." And I certainly would.