We’re off to see the Wizard, the wonderful Wizard of Oz!”

Researchers in Spain are working on a plan to build a human heart. Yes, a human heart.

They’ve already built replacement bladders, ears, noses and other relatively simple parts through the miracle of stem-cell technology.

A human heart, however, is by far the most complicated task thus far undertaken.

In Frank Baum’s classic childhood book, “The Wizard of Oz,” Dorothy and her little dog Toto set out on the Yellow Brick Road to persuade the Wizard to send them home. They, you will recall, had been swept up by a huge tornado (spawned, no doubt, by global warming) from their farm in Kansas and then set down in the Land of Oz.

While off to seek the Wizard, Dorothy teams up with a scarecrow who needs a brain, a tin woodsman who wants a heart, and a cowardly lion who desperately yearns for courage. When, after many adventures, they reach the Wizard’s palace, he proves to be a charlatan, as most wizards are.

He is also, however, a clever charlatan, and he sends the Scarecrow, the Tin Woodsman and the Cowardly Lion away respectively, with a “brain,” a “heart” and an ample dose of “courage” that, while not exactly real, are somehow certified by the Wizard.

Anyway, Dorothy and Toto eventually find their way back to Aunty Em and the farm.

But you know the rest of that story.

Back to medical science and human replacement parts: We hope that researchers do not stop when, in an estimated 10 years or so, they succeed in building a usable human heart.

There is a crying need for an even more complicated replacement part, a part ever so needed now, not in the Land of Oz, but in the not-so-mythical District of Columbia — on Capitol Hill, in the White House and in the Federal Reserve.

It’s a functioning human brain.