Vitamin E was discovered in 1922 by Herbert M. Evans and K. S. Bishop, who first noticed that laboratory rats failed to reproduce when fed a diet in which lard was the only source of fat. According to the researchers, a mysterious compound, extracted from both wheat germ and lettuce, was able to correct the problem.

For a time, the unknown component was termed the "anti-sterility factor". In 1925, however, Evans decided that, since vitamin D had recently been discovered, the new factor should be known as vitamin E. Some time later, he also proposed the name tocopherol (from two Greek words, roughly meaning childbirth).

Under either name, the new vitamin was clearly fat-soluble. Studies by Evans and his coworker Gladys A. Emerson (1903-) showed that its deficiency, in small lab animals, caused reproductive problems in both sexes, and a definite muscle dystrophy in many species. For almost...