The facts brought out by laborious experimentation are so well illustrated by human and animal experience in general, that it seems remarkable that so many physiologists and students of nutrition failed for such a long time to observe the evidence and to give it proper interpretation. Experience at the Wisconsin Experiment Station afforded the author an opportunity to contrast the superior growth and health of swine fed on satisfactory rations, with the poor growth in the scrawny, stiff-legged creatures so often seen on farms where the owners had not learned that it is not possible to keep a pig in a dry lot and feed it on grain, without resulting failure in pork production. It was at that time known to many shrewd animal husbandry-men that there are but two methods for feeding swine for profitable results. One was to feed the grain grown on the farm while the animals were running on a good pasture such as a clover or alfalfa field may furnish. The other was to feed the grain supplemented with liberal amounts of skimmed milk. A combination of these two plans leads to still better results.

While the investigations were in progress which have led to our present understanding of the science of nutrition, observations such as those emphasizing the inadequacy of diets consisting solely of vegetable products, the functions of which are those of storage organs, caused me to inquire into the dietary habits of man and animals with a view to finding, especially what relatively simple diets, composed of but one or a few articles, were at least reasonably successful in promoting well-being. Such an investigation into data which Nature presents for contemplation, revealed at once three important facts, which serve as the guiding principles upon which the experimental data since accumulated have been interpreted.