PART I EXPLANATORY LESSONS (continued 2)

The carbohydrates, both starch and sugar, in the process of digestion are converted into glucose. This is stored in the liver in the form of glycogen, which the liver has the power of manufacturing; it then passes into the circulation, and is distributed to the different parts of the body as it is needed. (The liver also has the power of forming glycogen out of other substances than sugar, and it is pretty conclusively proved that it is from proteids, and not from fats. Carnivorous animals, living upon flesh alone, are found to have glycogen in their bodies.)

It is impossible to assign any especial office to the different food principles; that is, it cannot be said that the carbohydrates perform a certain kind of work in the body and nothing else, or that the proteids or fats do. The human body is a highly complex and intricate organism, and its maintenance is carried on by complex and mysterious processes that cannot be followed, except imperfectly; consequently, we must regard the uses of foods in the body as more or less involved in obscurity. It is, however, generally understood that the proteids, fats, and carbohydrates each do an individual work of their own better than either of the others can do it. They are all necessary in due amount to the nutrition of the body, and doubtless work together as well as in their separate functions. They are, however, sometimes interchangeable, as, for instance, in the absence of the carbohydrates, proteids will do their work. The carbohydrates are eminently heat and energy formers, and they also act as albumen sparers.

The body always has a store of material laid by for future use. If it were not for this a person deprived of food would die immediately, as is the case when he is deprived of oxygen. (Air being ever about us, and obtainable without effort or price, there is no need for the body to lay by an amount of oxygen; consequently only a very little is stored, and that in the blood.)

The great reserve forces of the body are in the form of fatty tissues, and glycogen, or the stored-away carbohydrates of the liver; the latter is given out to the body as it is needed during the intervals of eating to supply material for the heat and energy of daily consumption, and in case of starvation. That they are true reserves is shown by the fact that they disappear during deprivation of food. The glycogen, or liver-supply, disappears first; then the fat (Martin). The heat of the body can be maintained on these substances, and a certain amount of work done, although no food except water be taken.

The principal function of the liver is to form glycogen to be stored away. It constantly manufactures it, and as constantly loses it to the circulation. Glycogen is chemically allied to starch, having the same formula (C₆H₁₀O₅), but differing in other ways. Its quantity is greatest about two hours after a full meal; then it gradually falls, but increases again when food is again taken. Its amount also varies with the kind of food eaten: fats and proteids by themselves give little, but starch and sugars give much, for it is found in greatest quantity when these form a part of the diet.

Inorganic Matter and Vegetable Acids. Water and other inorganic matter, as the salts of different kinds, and vegetable acids, as vinegar and lemon-juice, can scarcely be said to be digested. Water is absorbed, and salts are generally in solution in liquids and are absorbed with them.

Water is found in all parts of the body, even in the very solid portions, as the bones and the enamel of the teeth; it also constitutes a large proportion of its semisolids and fluids, some of which are nearly all water, as the perspiration and the tears.

Water usually is found combined with some of the salts, which seem to act as regulators of the amount which shall be incorporated into a tissue. Water is a necessary constituent of all tissues, giving them a proper consistency and elasticity. The power of resistance of the bones could not be maintained without it. It is also valuable as a food solvent, assisting in the liquefying of different substances, which are taken up by the various absorbent tubes, conveyed into the blood, and so circulated through the body. Most of the water of the body is taken into it from without, but it is also formed in the body by the union of hydrogen and oxygen.[29]

Sodium chlorid, or common salt, is found in the blood and other fluids, and in the solids of the body, except the enamel of the teeth; it occurs in greatest proportion in the fluids. The part that this salt plays in nutrition is not altogether understood. "Common salt is intermediate in certain general processes, and does not participate by its elements in the formation of organs" (Liebig). Salt is intimately associated with water, which plays an intermediate part also in nutrition, being a bearer or carrier of nutritious matters through the body.

Salt seems to regulate the absorption and use of nutrients. It is found in the greatest quantity in the blood and chyle. It doubtless facilitates digestion by rendering foods more savory, and thus causing the digestive juices to flow more freely. Sodium chlorid is contained in most if not all kinds of food, but not in sufficient quantity to supply the wants of the body; it therefore becomes a necessary part of a diet.

Potassium chlorid has similar uses to sodium chlorid, although not so generally distributed through the body. It is found in muscle, liver, milk, chyle, blood, mucus, saliva, bile, gastric juice, and one or two other fluids.

Calcium phosphate is found in all the fluids and solids of the body, held in solution in them by the presence of CO₂; both it and calcium carbonate enter largely into the structure of the bones.

Sodium carbonate, magnesium phosphate, and other salts play important parts in nutrition.

The various salts influence chemical change as well as act in rendering food soluble. For example, serum albumen, the chief proteid of the blood, is insoluble in pure water, but dissolves easily in water which has a little neutral salts in it.[30] Salts also help to give firmness to the teeth and bones.

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.)

A diet largely of animal food leaves very little undigested matter. The albuminoids in all cases are completely transformed into nutriment. Fat enters the blood as a fine emulsion.

Absorption. The general rule of absorption is that food is taken into the circulation through the porous walls of the alimentary tract as rapidly as it is completely digested. A large portion of liquid is immediately absorbed by the blood-vessels of the stomach.

Adaptation of Foods to Particular Needs and Conditions. The demands of different individuals for nutrients in the daily food vary with age, occupation, and other conditions of life, including especially the peculiar characteristics of people. No two persons are exactly alike in their expenditure of muscular and nervous energy, so no two will need the same amount or kind of nutriment to repair the waste.

A man who digs in a field day after day expends a certain amount of muscular energy. A lawyer, statesman, or author who works with his brain instead of his hands uses nervous force, but very little muscular. Brain and muscle are not nourished exactly by the same materials; therefore, the demand in the way of nutriment of these two classes will not be the same.

The lawyer might find a feast in a box of sardines and some biscuit, while the field laborer would look with contempt upon such food, and turn from it to fat pork and cabbage. This is no mere difference in refinement of taste, but a real and instinctive difference in the demands of the two constitutions. Sardines supply to the brain-worker the material he needs, and the pork and cabbage to the laborer the heat and energy he expends.

In health the sense of taste is the best guide to what is demanded by the system, and may as a general rule be followed; but in sickness that will not do, as the sense of taste in particular is disturbed by most forms of disease.

When a patient is very ill only the simplest foods will be used, and those will be prescribed by the physician; but when a patient is out of danger, and the necessity for variety comes, then the nurse, by preparing or suggesting dishes, may do much toward restoring the person to health and strength.

As a very large percentage of diseases arise from imperfect nutrition (as large as eighty per cent. being given by some writers), the sense of taste is usually very much disturbed and dulled in illness; therefore those kinds of food which are savory, and at the same time easy of digestion and nutritious, should be selected. The savory quality is very important. A person in health may endure badly cooked food and monotony in diet; a person recovering from an illness cannot but suffer by it.

A nurse will find a pleasant field for the exercise of ingenuity in selecting and preparing such dishes as shall (1) be suited to the digestive powers of the patient; (2) shall be savory; (3) shall be sufficiently varied to supply all those materials which the depleted and exhausted body needs; and (4) shall be in such judicious quantity as shall increase nutrition, but never overtax the digestive powers.

The decision of No. 1 (food suited to the digestive powers) is the most difficult, and here again the doctor will advise for particular or peculiar diseases.

There are certain things which from their natural composition are more easy of digestion than others, such, for instance, as milk, eggs slightly coagulated and raw, beef tea with the juices in solution, cocoa milk, and cocoa, coffee, jellies, gruels, porridge from prepared grains (except oatmeal) when thoroughly cooked, oysters alive, rice, venison, and tripe.

No. 2, the savory quality, depends largely upon preparation, and is under the control of the nurse. A baked potato done in a hot oven, just to the point, and served immediately, is a delicious dish; overdone, or done in an oven of low temperature, and served lukewarm, it is very far from appetizing. A steak, if cut thin, salted, and broiled slowly, will be hard, dry, and lacking in flavor, but if it is cut thick, at least an inch and a half, better two inches, broiled for the first minute over very hot coals, and then slowly, that the heat may have time to penetrate to the center, and raise the whole to a temperature sufficiently high to cook it (about 160° Fahr.) without charring the outside, it will make a dish both wholesome and savory.

No. 3, the next consideration, is that of variety, and here the resources and judgment of the person in charge must come to the front. Only general hints can be given. Endeavor to supply some protein, some fat, some of the carbohydrates, and some mineral matter in each meal. Bread, grains, or potatoes will give the necessary starch. Sugar is usually supplied with drinks. Milk, eggs, meat, fish, and oysters will give protein; cream, butter, bacon, and the fat of other meats will furnish fat, and fruits and green salads give acids and mineral salts. For the latter, grapes, apples, carrots, onions, dandelions, and lettuce are very valuable. Grapes are composed of water with salts in solution, and glucose; both are absorbed with very little outlay from the system. The others are every-day foods, but science has taught that their instinctive use in the past has been a wise one.

No. 4, the quantity of food to offer to a sick person, will depend upon the individual. Give enough, but rather give to an invalid too little than too much, especially in the first days of using solid food; for after some forms of sickness there is great hunger, and one may injure himself by overeating at such a time. Furnish a little of each kind of food, but let that little be of good quality and perfectly prepared, so that every morsel is eatable. It is discouraging to any one to have set before him food such that much of it must be rejected uneaten. It is very encouraging, especially to an invalid, to be able to eat all that is brought him, and for this end cooking and serving are of great importance. It is necessary to adjust the proportions of the different kinds of foods to the needs of the consumer, otherwise all unnecessary material will be rejected from the body as waste, or will be accumulated in it to interfere with the workings of the different organs.

In general it may be said that the needs of no two individuals can be satisfied with exactly the same diet. In sickness it is the province of the physician to adjust the food to the condition of the patient. In convalescence the taste of the individual and the judgment of the nurse or attendant combined will usually not fail of good results. If an individual craves a certain dish, and there is no good reason why he should not have it, by all means procure it. Let only your judgment act. It may be something that you personally do not like. That should not influence a decision, provided, of course, that the food is not unwholesome.

We should bear in mind that a sick person is not in the same condition as ourselves, and that no matter how absurd his cravings may seem, they may be but perfectly natural longings for those substances which his depleted and exhausted system needs in order to be restored to health.

PART II RECIPES