Tom Hughes was doing all right, you know -- as normal as any guy ought to be -- until without any warning he was seized by a potato.

"Maybe you grew up on a farm and it's all coming back to you," it was suggested.

"No," he said. He has no background at all in potatoes, and went unobtrusively from Philadelphia, where he was born, to Haddonfield, N.J., and on to Syracuse University and the Peace Corps. He was a year in Iran. Then back to graduate school and he wound up in 1973 teaching elementary grades in the International School of Brussels.

It was there that, for no utterly compelling reason, he dreamed up a little exhibit on the potato. Very much as teachers are forever dreaming up little projects to interest pupils in sheep, carburetors, cheese, the battlefield of Shiloh and the glory of human civilization generally.

Except that the potato exhibit fascinated him more than his pupils, and for no known reason and in very short time the potato was absorbing an amazing percentage of his interest and energy.

He finally left the school in 1978 to found (this may knock you down) the Museum of the Potato in his house. Lately he has been traveling about America under the aegis of the Frito-Lay company, which makes potato chips among other things. It is not often, probably, that the company finds some fellow far gone in potato lore, but Hughes was smitten by the potato long before any commercial application occurred to him or anybody else.

He goes about with a sack of potatoes. They are in little bags, like samples of uranium ore or jawbones of Cro-Magnon Man.

His favorite variety is possibly the Eisenheimer, a German sort. Just here it should be said that American gardeners are sorely limited in the number of potato varieties available for planting in the home garden. Such standby corporations as Park's and Burpee offer only two varieties.

And yet like Cleopatra the potato is infinite in her variety.

"You sound as if you think the damn potato is greater even than corn," someone said to Hughes.

And he does. He orates at length on its merits. It has more Vitamin C than oranges, and if you spend any time with Hughes, a wholesome-looking man of 36 who appears to be about 24, you will soon start believing that if you eat a potato from time to time you will live forever in sublime health.

The potato comes, of course, from the uplands of Peru where it is still grown in endless varieties. Indeed, there is some interest now in gathering in the Peruvian sorts, as potential parents for new varieties of the tuber.

There is some cloudiness about the introduction of the potato into Europe. The Royal Horticultural Society (London), which takes the potato quite seriously, suggests (in its great Dictionary) the potato arrived in 1570 and was first planted in Spain. By 1588 it was an established vegetable in Italy.

Sir Francis Drake is believed to have brought the potato back from his New World journey in 1586, and it is thought Sir Walter Raleigh introduced it to his newly acquired estate in southern Ireland about that time, possibly from tubers brought back by Drake.

In any case, the great English herbalist, Gerard, first described it in 1597, and could not refrain from boasting mildly that he grew it as well in London as it ever grew in its native land.

But the truth is that the potato was poorly esteemed for centuries after its introduction. It was only in the terrible Potato Famine of 1845 that the world woke up to the fact that the potato was an immensely important crop.

The Irish had depended on it for some time. "It was probably sheer necessity," the RHS Dictionary presumes.

But it was not only Irish peasants. The Scots turned to potatoes in a time of great destitution and famine in the mid-1700s. The potato has of course been a staple of the Western World for many decades now. The Germans made fuel from potatoes during World War II. The Polish make vodka from the noble vegetable.

Potato chips are said to have been invented in 1853 at the Moon Lake House Hotel at Saratoga Springs. Cornelius Vanderbilt ordered french fries, but wanted them thin as in France. The chef, annoyed as chefs always are if you don't like what they automatically dish out, cut them paper thin in a snit.

Unlike most fits of pique, this experiment was successful.

Hughes has an astounding number of bashers, mashers, peelers and other ingenious inventions in his museum, all at the service of the potato. He has movies on the potato. He has a print of van Gogh's "Potato Eaters," and recordings of Louis Armstrong's "Potato Head Blues." He has a representative, and possibly unrivaled, collection of potato sacks.

The fact that no museum was dedicated to the potato amazed Hughes, more than others, perhaps. He is pleased to have corrected this fundamental gap in world culture.

He cannot say, really, why the lore of the potato so seized his imagination. Nor could Parsifal, perhaps, say exactly how it happened that he went after the Grail, more than others.

Hughes smiles much of the time and is bright-eyed and full of beans. Because he eats so many potatoes.