A man may eat his fill and yet be hungry. It is not the quantity but the proper quality in food that satisfies. It is not only true that what is one man's food is another's poison; but it is also true that what is food atone season of the year, at one period of life, or in one climate, may be poison to the same individual at another season or age, or in another climate. The inhabitant of the tropic subsists and thrives on fruits on which the Icelander would starve; while the blubber and oil that makes up the diet of the inhabitant of the frozen zones would be fatal to those who live under the burning sun of the equator. Even the same person requires a fruit diet in the tropics, and one of fats in the north region. The child requires food made up of different elements from that which best suits the adult; and the diet of a laborer in the open air must differ from that of the brain-worker, who takes little exercise, and whose work makes heavy draughts on the nervous system.
No one has mastered the art of cooking who does not know something of the chemical elements of foods, and the purpose they serve when taken into the system. It is particularly important that those who are compelled to practice rigid economy should know just what foods will best supply the real needs of the family, and how the most real nourishment may be had for their money.
An adult takes into the system daily, through lungs and mouth, eight and a quarter pounds of dry food, water, and air necessary for respiration. The same amount is given off as waste through the pores, lungs, kidneys, and intestines. Life and activity consume this amount as fuel just as a lamp consumes oil. Every movement, every breath, every heart-beat, every thought burns up a certain amount of fuel-material, and if the supply is not forthcoming, the machinery stops and death ensues. The better the oil the more perfect the light; and the more perfectly the food is adapted to its wants, the more vigorous the body, and the more perfect the working of its intricate machinery of muscle, nerve, and brain.
Food is first masticated and then digested. In mastication it is not only moistened with saliva, but acted upon chemically in preparation for the more vigorous and thorough work of the stomach. It is a mistake to suppose that water or any of the various drinks taken at table are a substitute for saliva. They not only do not prepare food for the stomach, but force it into the stomach unprepared, and, besides, retard digestion by delaying process until the water can be absorbed into the blood. For these rea-sons drinks should precede or follow a meal. Crusts of bread and hard and firm food is wholesome, principally because it must be thoroughly masticated before it can be swallowed.
When the food reaches the stomach it rouses into action, the gastric juice pours from hundreds of little points, the food is diluted and the more solv-parts dissolved, to be taken up by the thousands of little mouths which honeycomb the surface, and carried into the circulation to repair the waste of tissues. The oily portions of food, and such as do not yield to the action of the gastric juice, pass on and are subjected to the influence of the bile and pancreatic fluid, until all that is of value is absorbed, while the waste is rejected and passes off. (592)
This much of the digestive process needs to be known to make clear the why of certain processes in cookery. As the juices of the stomach only act on the surface of the food which passes into it, it is easy to see why light bread is more wholesome than heavy. The gastric and other juices can act only on the outside surface of a heavy lump of dough; but when made into light and porous bread, the outer surface is not only vastly increased, but the juices pour through thousands of avenues, and penetrate and act on every part. If the frugal housewife knew this, would she set the heavy, soggy loaf of bread before her children "to save it?" Many a mother ig-norantly gives her child a stone when it asks for bread.
Fats of all kinds do not digest in the stomach. The gastric juice mingles with but does not dissolve them. It is only after they have passed on and become subjected to the action of the bile and pancreatic fluid that they are taken up and made available as carbon for lung combustion. Fats, un-combined with other substances, act as emetics or cathartics and not as food. It is only when combined with other food that they are capable of being taken up by the absorbing vessels, and made to act as fuel to the system. A half pound of crude lard, unmixed with any other substance, would be rejected, but when thoroughly and skillfully mixed into a flakey crust will not derange the stomach, and will be assimilated and utilized. Remember that the use of more fat than can be perfectly blended, or any carelessness or imper-fection in the process, is sure to produce indigestion and work mischief.
Foods differ in the time required for digestion. Some fruits refresh instantly, the juices being at once absorbed into the circulation. Some meats and vegetables yield almost immediately to the action of the gastric juice, and pass into the circulation. Others require a long time for digestion. The more subtle and delicate flavors and parts of food yield first; then the gluten of the flour, the curd of the milk, the fiber of the flesh, reinforce the blood and supply muscular waste, while, later, the oily and sugary portions are worked over to repair waste or furnish fuel to keep up the heat of the body.
Food has chiefly two offices to perform: the repair of muscular waste, and the supply of the body with fuel to keep its heat up to 98°. Each of these is indispensable to health and strength. The chief part of what we eat is used by the lungs for fuel; the rest, excepting small portions of mineral substances, such as lime, potash, sulphur, etc., goes to the production of muscular and brain force. The great secret in the preparation of food that will prolong life and maintain a high state of health, is to adapt it to the peculiar conditions of those to be fed, - age, occupation, climate, and season to be considered. Variety of food is nearly always at hand; knowledge only is necessary to choose that best adapted to present needs.