The fate of ingested food materials presents a problem of serious concern to the physician. If the digestive glands fail to supply a suitable quota of their secretions, the conversion of the digestible nutrients to products adapted for absorption may be interfered with. If the motor functions of the alimentary tract are impaired, the enforced stagnation of food residues may render them more prone to bacterial decomposition and thus afford an opportunity for the genesis of undesired products of fermentation and putrefaction that are more or less harmful. So long as both motor and secretory activities remain normal, the familiar nutrients such as the proteins, fats, starches, sugar, salts and vitamins are likely to disappear from the gastro-enteric tract with physiologic efficiency. The "coefficient of digestion" for such compounds is ordinarily excellent, so that more than 90 per cent are utilized and hence fail to reappear in the stools.