The science of cookery is an important branch of pharmacy, in the broad sense, the decision as to the quality of a food stuff, an important branch of pharmacognosy, and the management of the diet by the physician, a branch of therapeutics. The quantitative estimate of foods consumed, and a knowledge of their active, nutritive principles, is quite as necessary as a knowledge of drug dosage, with the proviso that the necessity for accuracy in the amounts prescribed is inverse to the powerfulness, that is, the toxicity of the substance administered. While in health a normal appetite or even habit may be a tolerably safe guide to the nature and amount of the food ingested, quantitative estimates become necessary in disease, especially as the disease influences or is influenced by metabolism, so that the avoidance of an excess or deficit or the purposive creation of an excess or deficit of