Michaud (26) sought to verify with experiments on dogs, the theory that the more similar the food proteins to those of the tissues which they are destined to form in the body, the higher would be their biological value as nutrients. He allowed dogs to fast for a time to reduce their nitrogen output to the minimum of tissue destruction. He then fed them a non-nitrogenous diet supplemented with various amounts of protein from different sources. His findings lead us to the belief that the proteins of the same species of animal are superior in dietary value to proteins obtained from another species or from plants. Dog muscle and dog serum proteins were of higher nutritive worth for the dog than muscle or serum proteins from the horse. A mixture of dog tissues (muscle, blood and glandular organs) was also superior to any of the other proteins studied. Gliadin and edestin, proteins from the wheat kernel and hempseed respectively, were of the lowest value. We now know that his diets were by no means comparable in their quality with respect to factors other than protein. All except those in which the glandular organs were included were very deficient in the anti-neuritic, anti-ophthalmic and anti-scorbutic substances, as well as very poor in their mineral content. It is not possible, therefore, to accept without doubt his interpretation of his results.