In the early 1900s, Pellagra was a common disease that caused symptoms such as diarrhea and dementia. Joseph Goldberger performed the initial experiments that identified Pellagra as a nutritional deficiency, but his experiments performed in humans were controversial, with the later ones actually inducing pellagra in prison inmates by withholding certain nutritious foods from the diet. Conrad Elvehjem furthered this work by performing controlled experiments in dogs. Elvehem noted that when dogs get pellagra, due to a poor diet, their tongues’ turned black. This “model system” allowed Elvehjem to give dogs different nutrients and see which extracts helped dogs recovered from the “black tongue” disease. Through careful purification of the food extracts, Elvehjem discovered that nicotinic acid was the agent that cured pellagra, or “black tongue” disease, in dogs. and