It would be contrary to the principles of physiology to attempt to feed the bones by consuming a large excess of phosphorus in the food or the muscles by confining the food to a purely nitrogenous component. Such attempts, instead of nourishing the tissues indicated, will so unbalance the rations as to disarrange the whole metabolic process, and thus injure and weaken the very tissues they are designed to support. It seems, therefore, advisable to prepare a manual which may be used in conjunction with works on dietetics and on physiology and hygiene and yet of a character not especially designed for the expert. The American public is now so well educated that any average citizen is fully capable of understanding scientific problems if presented to him in a non-technical garb. It is, therefore, not difficult to see that the great army of manufacturers and dealers in food products, as well as the still greater army of consumers, are able to receive and to utilize information concerning food products which is of common interest to all. A dissemination of knowledge of this kind will guide the manufacturer in his legitimate business and protect the public against deceptions such as those mentioned above. In the evolution of society, economy and efficiency indicate that specializations should be made as completely as possible. For this reason it is advisable that foods of a certain character be manufactured and prepared for consumption on a large scale, so that due economy and purity may be secured. On the other hand there are many other kinds of foods which, by reason of their properties, cannot be prepared on a large scale but must be produced near or at the place of consumption. Milk is a type of this class of foods. It is altogether probable, therefore, that the consumption of manufactured foods will not decrease but increase even more rapidly than the number of our population. In order that the people may be able to judge of the quality and character of products of this kind, information readily available appears to be highly desirable. In the other case of the utilization of raw materials, it is equally important that the people of this country understand their nature and their functions in the digestive process. The great nutritive value of our food is found in the cereals, the meats, the fruits, and vegetables which we consume. A description of foods of this class, the places of their growth, the conditions under which they are matured and marketed, the problems which relate to their storage and transportation, their composition in respect of nutrition and digestibility, the dangers which may accrue from their decay, and the adulterations or sophistications to which they may be subjected are matters of the greatest public importance.