to create the perfect foods for farm animals. Due to discoveries by Justus von Liebig and others, they thought that any feed that contains a set amount of protein, carbohydrates, fats, salts, and water was equivalent to any other. Babcock did not believe them, and joked with his German colleagues that cows could survive on coal and ground-up leather according to their calculations. After Hart replaced him as department chief in 1906, Babcock and others created an experiment to test his hypothesis. Sixteen calves were purchased on the market. One was part Jersey and one was part Guernsey. Three out of four groups of calves were given feed prepared from a single grain and raised until they had had two pregnancies. One group received wheat, the second received oats, while the third ate only corn. A fourth group received a combination of all three grains. After the first year, only the corn group was thriving, and the others and their young were weak or dying. The wheat group was the worst off, and the oats and mixed groups were in between. Then the weak cows were fed corn. They recovered and bore healthy calves. Hart and his team published their findings in 1911 in Physiological Effect on Growth and Reproduction of Rations Balanced from Restricted Sources. The researchers and Babcock, the leader, could see the results but, they write, "At present we have no solution for the observations made." McCollum summarized, "something fundamental remained to be discovered." Rat colony Searching for a breakthrough in human and animal nutrition, McCollum purchased all thirty-seven volumes of Richard Maly's Jahresbericht Über Die Fortschritte Der Tier-Chemie so he could read them at home. He read of about 13 experiments done between 1873 and 1906 on small animals, often mice, fed restricted diets. In all cases, the animals failed to thrive and died in a few weeks. McCollum determined that he must find out what was lacking in their purified diets, and that he needed to experiment on animals with a short life span, finally deciding on rats. Rats are omnivorous, and cheaply fed, matured quickly, and "had little sentimental and no positive economic value". The dean of the college of agriculture would not support experiments with what he feared was vermin, but Babcock, who was retired, understood the rats' importance and told McCollum to proceed. Using skills he developed with his brother when they