Elmer Verner McCollum was a distinguished biochemist, organic chemist, and nutritionist who studied nutrition and its effects on health and metabolism. The discoverer of vitamins A, B and D, McCollum also found the nutritional cause of rickets, a bone disease. His twenty-six years of research at the School of Hygiene and Public Health at the Johns Hopkins Medical School in Baltimore continued his earlier research and made him an authority on how diets lacking certain vitamins or trace minerals can cause diseases. He developed a biological method to analyze foods and popularized the use of rats as an extremely valuable experimental model. By modifying the rats' diets, McCollum produced animals with rickets. Because of these studies, rickets, a disease in which bones become deformed, is virtually nonexistent in developed countries. In a field of research that had few findings of importance for decades, he was instrumental in ushering...