In the 1930s, scientists began to search for a missing member of the B family--this one, a vitamin that could cure acrodynia, a skin disorder in rats that appeared to resemble the human disease, pellagra. Pellagra was already known to be a deficiency disease that could be prevented or cured by adding niacin (vitamin B₃) to the diet. Logically, then, niacin should work on acrodynia as well. But in 1934, Paul György (1893-) discovered that it didn't work at all. Moreover, György--a Hungarian-born physician who emigrated to the United States--had earlier learned that neither vitamin B₁ (thiamine) nor vitamin B₂ (riboflavin) has much effect on the rat- pellagra either. György was so convinced that a curative factor did exist, however, that he proposed the name vitamin B₆ for it, if and when it was found.

And a few years later,in...