The starch globules in cereals and vegetables are in the form of cells, the covering of these cells being composed largely of nitrogenous matter. The protein is not acted upon by the saliva, and the nitrogenous matter is largely digested in the stomach. It is more easily dissolved if it is broken or softened by cooking, so that the carbohydrates can come in contact with the saliva, but if encased in fried fat, the gastric juices cannot digest the protein covering and the saliva cannot reach the starch until the fat is emulsified in the intestines. This means that wherever starch globules are surrounded with fat, the digestive ferments reach these globules with difficulty and fried foods must be digested mostly in the intestines. Fats are readily absorbed in their natural condition, but when subject to extreme heat, as in frying, they are irritants. For this reason, eggs, poached, boiled or baked are more easily digested than fried. _Boiling, broiling and roasting are preferable to foods cooked in fats._ * * * * * [Sidenote: Cooking of Cereals] One safe rule for the cook is, that it is better to cook most foods too much than too little; overcooking is uncommon and harmless, while _under_cooked foods are common and difficult of digestion. In partially cooked cereals, one does not know how much of the cooking has been done, but it is safe to cook all such foods at least as long as specified in the directions. One reason why breakfast foods, such as rolled oats, are partially cooked, is because they keep longer. As has been stated, the nutrients of the grain are found inside the starch-bearing and other cells, and the walls of these cells are made of crude fiber, on which the digestive juices have little effect. Unless the cell walls are broken down, the nutrients can not come under the influence of the digestive juices until the digestive organs have expended material and energy in trying to get at them. Crushing the grain in mills, and making it still finer by thorough mastication breaks many of the cell walls, and the action of the saliva and other digestive juices also disintegrates them more or less, but the heat of cooking accomplishes the object much more thoroughly. The invisible moisture in the cells expands under the action of heat, and the cell walls burst. The water added in cooking also plays an important part in softening and rupturing them. Then, too, the cellulose itself may be changed by heat to more soluble form. Heat also makes the starch in the cells at least partially soluble, especially when water is present. The solubility of the protein is probably, as a rule, somewhat lessened by cooking, especially at higher temperatures. Long, slow cooking is therefore better, as it breaks down the crude fiber and changes the starch to soluble form without materially decreasing the solubility of the protein.