The last decade of research in the field of animal nutrition has Ied to the discovery of a new class of substances in the food stuffs constituting the animal dietary. These compounds have been designated "Vitamines, Accessory Factors of the Diet, Exogenous Hormones of the Diet". They are present in infinitesimal quantities in certain articles of the diet, but their role in the metabolic cycle is one of the greatest importance. Subsequent investigation has shown that they are essential for the wellbeing and even the life of the organism itself. Without these indispensable elements the animal cell is unable to maintain its activities unimpaired, or the adolescent subject to attain normal growth. Continued deprivation leads to disease and ultimately to cessation of life. The discovery of these cornpounds was the result of a generation's work on the etiology of two diseases - Beri-beri and Scurvy. These are now known as "Deficiency Diseases". Each of these pathological conditions is due to the dietary deficiency of a specific substance, which in the case of beri-beri is known as the "Anti-neuritic Vitamin" (Funk); "Water Soluble B substance" (McCollum). In the case of scurvy this element is called the "Antiscorbutic Substance". A third factor associated with fats of animal origin has been subsequently discovered, but its deficiency results in a general malnutrition of a chronic type complicated with Xerophthalmia
