During his experiments with riboflavin, Gyorgy has noticed that rats already on a thiamine-only diet developed pellagra-like symptoms, even when given pure riboflavin. The symptoms were only relieved when rats were given supplements derived from a flavin-free extract of bakers' yeast. In contrast, rats given this extract but no riboflavin failed to exhibit pellagra-like symptoms but were unable to gain weight until riboflavin was added back into the diet.