To recapitulate, food is eaten, digested, assimilated, and consumed or transformed in the body by a series of highly intricate and complex processes. It is for the most part used for the different powers and activities of the system; there is, however, always a small portion which is rejected as waste. The first change is in the mouth, where the food is broken up and moistened and the digestion of starch begins; these changes continue in the stomach until the whole is reduced to a more or less liquid mass. As the contents of the stomach pass little by little into the duodenum, the mass becomes more fluid by the admixture of bile, pancreatic juice, and intestinal juice, and, as it passes along, absorption takes place; the mass grows darker in color and less fluid, until all good material is taken up and only waste left, which is rejected from the body. That portion of the food which is not affected by the single or united action of the digestive fluids is chiefly of vegetable origin. Hard seeds, such as corn, and the outer coverings of grains, such as the husk of oatmeal and those parts which are composed largely of cellulose, pass through the intestinal canal without change. It may be remarked here that since the digestive mechanism is so perfect a structure, and will try to dissolve anything given it, and select only that which is good, why should there be the necessity of giving any special attention to preparing food before it is eaten? The answer is that the absorptive vessels cannot take up what is not there, neither can the digestive organs _supply_ what the food lacks; therefore, the food must contain in suitable proportions all substances needed by the body. Also, food which contains a large proportion of waste, or is difficult of digestion from over or under cooking, or is unattractive by insipidity or unsavoriness, overworks these long-suffering organs (the extra power or force needed being drawn from the blood), and causes the whole system to suffer. Mal-nutrition, with the long line of evils which it entails, is the cause, direct or indirect, of most of the sickness in the world, for it reduces the powers of the system, and thus enfeebles its resistance to disease. =Ideal Diet.= "The ideal diet is that combination of food which, while imposing the least burden upon the body, supplies it with exactly sufficient material to meet its wants" (Schuster). In general the digestibility of foods may be summarized as follows: 1. The protein of ordinary animal foods is very readily and completely digestible. 2. The protein of vegetable foods is much less easily digested than that of animal foods. 3. The fat of animal foods may at times fail of digestion. 4. Sugar and starch are easy of digestion. 5. Animal foods have the advantage of vegetable foods in that they contain more protein, and that their protein is more easily digested. (Atwater.)