Before discussing the question of suitable foods for individual needs or the ill-health which is so likely to follow an unrestrained or unwise diet, it will be well to trace briefly the passage of food through the human body, with the various changes which take place in its mass from the time it enters the mouth until it is absorbed by the stomach.

The human mechanism.

In a little book by Hough and Sedgwick entitled "The Human Mechanism," the authors point out that in many respects the human body is like any machine developing energy by the conversion of certain kinds of raw material. Thus, as the steam engine will use up coal in the development of mechanical energy, so the human body will absorb food and convert it into vital energy, and it is quite as important that the human body shall have its source of energy properly adjusted to its needs as that the steam engine shall be fired with coal possessing a reasonable amount of heat-producing particles.

The human body requires this supply of raw material for several different purposes. In the first place, the very fact of living uses up each minute a number of cells of various kinds in various organs. Each breath taken, each heart beat, each muscular motion, all tend to the destruction of tissue and involve its reconstruction. Violent exercise uses up cell tissue very rapidly, so much so that a football player will commonly lose from five to ten pounds in weight during a well-contested game. It is a fundamental principle of training for any athletic event involving hard exercise, that suitable food in large quantities must be provided, and a young man training for football or rowing will eat beefsteak, eggs, and other hearty food to an astonishing amount, all of it going chiefly to repairing worn-out and used-up tissue.

In the second place, food is needed to supply material for growth, and so it is that a growing boy eats out of all proportion to his size, and the fact that he seems to be, as it is said, hollow clear to his feet, is only his rational endeavor to supply the material needed for his growing body.

In the third place, food must be supplied for the work to be done by the body, as distinguished from the loss of tissue due to the performance of the work, and finally, food must be provided in order to maintain the bodily temperature, a larger amount being naturally required where the difference between the temperature of the body and the outside air is very great, as in the Arctic regions.

The human body being a special kind of machine, the raw material supplied must be adapted to the needs of the machine, and while a lump of coal admirably supplies energy for a steam boiler, no one would think of feeding a lump of coal to a human being, simply because, by experience, we know that suitable energy is not thereby developed. In the matter of suitability of foods, much depends upon the local supply. It is not to be supposed, for example, that the Eskimos eat meat and fat altogether because it is the best article of food for them, but rather because it is the only food available. It would be foolish to prescribe fresh fruit or even white bread for the Eskimos because it is out of the question for them to get such food. But, in general, it is possible for the average individual to choose his supply of raw material in accordance with the needs which his experience has pointed out and with the teachings of scientific investigators on this subject. Raw material, however, is not converted into energy by any simple operation. The human body is made capable of taking raw material of most varied kinds and transforming it into nutriment capable of being absorbed by the system and made over into cell tissue. It will be worth while to indicate the steps of this complex process.

Digestive processes.

The mouth plays the first part in the scheme of transformation, and here two operations are performed. First the food is crushed and ground by the teeth, exactly as when, in some chemical processes, a fine grinding is essential for the subsequent transformation. In this country, this preliminary process is often sadly neglected, so much so that a distinguished investigator, named Horace Fletcher, has, within the last few years, established a school for the cultivation of the habit of chewing, with the idea that if this practice could be encouraged and at least twenty chews taken with every mouthful, the health of the individual would be vastly improved and sick persons even cured merely through this practice.

The other function of the mouth is to mix with the food the saliva which drops from small glands in the back of the mouth into the food. The action of the saliva is partly to lubricate the food, so that it will slip down easily, and no better proof of this can be found than trying to eat a cracker rapidly without chewing. But it also acts on starch which is not digested easily unless mixed with this ferment. The action of the saliva on starch is to convert it into sugar, which is easily absorbed later on. Curiously enough, most persons would be more apt to chew a piece of meat thoroughly than to chew a piece of bread, and yet the meat contains practically no starch and therefore does not need the action of the saliva, whereas bread is chiefly made up of starch and therefore needs the saliva as an essential for digestion.

The food then passes down into the stomach, which is a sort of storehouse, preparatory to the really important steps in digestion. Here, the food is acted upon by another element known as gastric juice, which is supplied by small glands found in the membrane of the stomach. The mixture of food and gastric juice is made very thorough by the continual agitation of the food, so that the mass is softened as well as thoroughly mixed. The effect of the gastric juice is to act upon that portion of food known as proteids. Examples of almost pure proteids are found in the fiber of beef and other meat, in the yolk of eggs, and in cheese. Some vegetables, such as peas, also contain large quantities, and coarse flour and oatmeal contain considerable percentages. The effect of the gastric juice on this proteid matter is to break up the complex molecules into small molecules which then pass into solution, making the mass leaving the stomach a uniformly mixed semiliquid substance of about the consistency of thick pea soup. The food then enters the smaller intestine, at the beginning of which the juices from the pancreas are added. The pancreas is a gland which furnishes a strongly alkaline liquid neutralizing the acid of the gastric juice, so that the gastric agent, pepsin, loses its power. From this gland comes a material which can act on all kinds of food and which is by far the most important of the digestive juices.

When thoroughly mixed with the bile and pancreatic juice, the contents of the intestine are gradually absorbed, in so far as their condition allows, by the surface of that organ and are carried away by the ducts designed for that purpose to the various organs, while that part not suited for absorption is eliminated.

Teachings of the digestive operations.

The matter of hygienic eating, therefore, consists in supplying the various organs, the mouth, the stomach, and the smaller intestine with proper food in proper quantity, so that the body itself may be properly nourished from the food supplied. A great deal of scientific investigation in this connection has been made to ascertain any relation which may exist between the different kinds of food and their availability for the body. Scientists have divided all food into four classes, namely, proteids, carbohydrates, fats, and inorganic salts, and they have agreed on the following general statements with reference to these four classes. Examples of almost pure proteids have already been given, and it may here be added that carbohydrates are typically shown by the starchy particles found in potatoes or wheat. Chemically, the difference consists in the fact that proteids contain nitrogen whereas carbohydrates do not. Fats are self-explanatory, and the group of inorganic salts includes such material as salt, lime, phosphates, and other minerals needed by the body but not requiring digestion.

Just what function each one of these four groups plays in the nutrition of the human body is not definitely understood, but it seems that the proteids are particularly useful in building up cell tissue, that the carbohydrates are particularly useful in providing for muscular energy, that the fats are particularly useful in keeping up the normal warmth rather more by laying on a blanket of fat over the bones than in actually consuming the food in the creation of heat. These statements are not absolute, since experiments have shown that some tissue-building can go on even if proteids are rigorously excluded from the diet, and on the other hand that muscular work, while accompanied by a large consumption of carbohydrates in the body, may come from proteids entirely. This may explain why men can live and even do a reasonable amount of work eating meat and fat altogether, as in the Arctic regions, or dry bread and fruit in other regions, the above facts being complicated by the influence of muscular exercise on the activity of the digestive system.

No principle of hygiene is better established than that men undergoing hard physical exercise need and will take care of a larger amount of coarse food than those occupied in sedentary work. In cold weather what is required is not really more fat as food, but more food. It has been found that there is a limit to the amount of meat food which the body can absorb, and, further, that the excess is not easily disposed of, as with starchy food, and tends to load up the liver and other organs with the waste products, resulting in general disturbances of the whole body. It is commonly known, for instance, that high-livers, as they are called, are likely to be troubled with diseases like indigestion, rheumatism, or gout,—diseases which are the result of overburdening those organs just mentioned.

Balanced rations.

TABLE XVI

A well-designed food ration, therefore, will be one which will provide the body with the proper amount of food material wisely adjusted to the occupation and the digestive ability of the individual. It has been, in the past, a matter of very exact computation to determine how many ounces of proteid food, how many ounces of starchy food, and how many of fatty foods should be consumed during the day, and experiments have been made in asylums, prisons, and on companies of soldiers with a view to proving the theoretical figures.

It has always been found that an overdose of proteids results in inability to absorb the excess, and it has been assumed that a ratio of proteids to carbohydrates of one to four is approximately the proper proportion. For instance, Koenig (1888) shows the minimum daily need of food stuffs at different ages and two American authorities, Atwater and Chittenden, have also laid down standards; all three being shown in the preceding table.

The following table taken from Rough and Sedgwick's book, already referred to, gives the percentage composition of some of the more common foods:—

TABLE XVII

It will be noted that meats, cheese, and such vegetables as peas are high in proteids, while certain other vegetables, as rice and white flour, are high in starch or carbohydrates. According to the table given above, a man at moderate work requires 4.1 ounces of proteids and 17.5 ounces of carbohydrates per day. If, then, the carbohydrates were to be made up entirely from potatoes, 18 per cent of which is starch and he should need 17.5 ounces, he must have 100/18 of 17.5 or 97 ounces of potatoes per day, an amount equal to about 6 pounds. If, however, with the potatoes, he should eat half a pound of bread, of which about half is carbohydrates or 8 ounces, the amount of potato necessary would be cut down, and so on with as many combinations as one might choose to make.

It is curious, however, that when different kinds of food are available, one naturally combines different articles of food, so as to make up the well-balanced daily ration, so that the different parts may have the proper proportion. For instance, butter is always used with bread in order to add to the proteid and starch of the bread the necessary fat. With potatoes or rice, either butter or gravy or meat is always used because potatoes and rice are lacking in proteids as well as in fats which the meat supplies. Bread and cheese are well known to make up a good combination, and the table shows why: the bread furnishing the starch and the cheese the proteid and fat. Eggs alone are a very poor article of diet since no starch at all is present, and therefore it is that when eggs are eaten for breakfast, as is so generally the custom to-day, either a generous helping of cereal ought to be given with the egg or else a generous supply of bread or toast ought to be included in the breakfast. Milk is generally considered an ideal article of food, and yet it contains no starch, and it is undoubtedly because of this fact that milk and bread is more palatable as well as more nutritious than milk alone.

Human appetite.

One other factor needs to be considered in this matter of selecting one's daily food, and that is the respect which must be paid to the appetite. The most carefully balanced ration will fail to satisfy the ordinary human being unless it is served attractively and unless sufficient variety is provided. To be sure, soldiers in the army are furnished a carefully computed ration consisting of so much meat, either fresh or salt, so much bread, and so much vegetable food, and the variety being small, the soldier has to put up with his dislike to the same food day after day. The need of fresh vegetables has been proved by the results of a continuous diet of salty food on certain classes of men, such as sailors.

It is well known that a failure to provide fruit or fresh vegetables results in the disease known as scurvy, for which, practically, the only cure is a changed diet. The writer has no doubt but that in many farmhouses a very similar condition, perhaps not so pronounced, exists on account of this very lack of variety in the daily menu. He remembers to this day a week's experience in the house of a well-to-do farmer in the early spring when the winter vegetables were exhausted and before summer vegetables appeared, when the dishes offered three times a day throughout the week were salt pork in milk sauce and boiled potatoes.

Providence intended the different digestive organs of the human body to work, and there is no possibility of condensed or concentrated foods taking the place of ordinary victuals, as has been suggested. The stomach must have some bulky material on which to work, and similarly the intestine must be comfortably filled in order to exert its forward movements. It is in the same way intended that each organ shall supply the necessary digestive juices to take care of the different kinds of foods taken into the system. It is just as important that the liver should be called upon to act on a certain amount of fat as that the gastric juice should break up the molecules of the proteid, and just as important as both of these is the fact that the saliva should flow freely to decompose the starch before it enters the stomach. It is not intended, however, that the healthy individual should deliberately overload any part of the digestive system.

If a child, in a hurry to get to school, swallows bread and milk without chewing and without allowing the starch to be acted upon in the mouth, then an overburden is placed on the pancreatic gland, making that organ less capable of its regular work. And if, again, the food is drenched in fat, if everything is fried, or if butter is used in large quantities, the liver becomes overworked and cannot keep up with the demands, and digestive troubles follow.

Effect of individual habits.

Assuming that the amount and quality of food have been properly adjusted, that each of the several constituents is in proper proportion, and that a suitable variety is maintained, there are still other phases to be considered before the nourishment of the individual may be considered satisfactory. Nature has furnished man with a guide both to the quantity and quality of food that should be taken into the system,—that is, his desire for food, or his appetite,—and, in general, this guide may be safely trusted both as to the quantity and quality, although, in the latter, the appetite is not so trustworthy as that of the lower animals.

Unfortunately, the appetite is easily distracted by the general conditions of health, and when once the healthy tone of the system has been relaxed, the appetite becomes misleading. For instance, a person not indulging in muscular exercise, but sitting still all day and eating candy or other sweets, has no desire for food, and the lack of appetite in this case indicates, not a failure of the need of food, but abnormal conditions of the system. Also the conditions of housing, lack of ventilation, excessive heat, excess in the use of stimulants or of food, all affect and interfere with the guidance of a normal appetite. Some persons go to the other extreme, and, having been in their earlier years accustomed to heavy exercise and generous feeding, forget that in a more quiet life, less breaking down of the tissue occurs and therefore less food is required. Their appetite is a poor guide since it leads them to immoderate eating, resulting in time in an overloading of the organs and the probable poisoning of the system.

Cooking.

Good cooking is as important as any other part of the process of digestion, and, in fact, cooking may be said to be the first step, since there the breaking down of the food tissue occurs, whereby subsequent action by the juices of the body is made easier. For instance, beef may be cooked so long and in such a way as to dry and harden the fibers, making it almost impossible for subsequent digestion; and on the other hand, it is possible to so stew or boil or steam tough meat as to make it quite easily absorbed by the stomach. Cereals, if properly boiled at the right temperature, and for the right length of time, will have the starch granules so broken up that the saliva will act easily on the broken granules. Raw vegetables containing starch are not acted upon in the mouth and are digested afterwards only with great difficulty, while cooked vegetables are a most desirable article of diet.

A great deal is said nowadays about overeating, and Horace Fletcher affirms that the average man would be much healthier and much stronger if he ate not more than two meals and generally only one meal a day. The relation between the amount of food eaten or the amount of food absorbed or utilized and the need for food cannot be determined for the average but only for the individual. There is no doubt but that men or women doing muscular work require greater amounts of food than those not so engaged. It is a common practice to increase the amount of oats which a horse consumes when the horse has hard work to do and to cut down the amount of grain when the horse stands in the stable. It is curious that this practice, so well known to give good results, is not applied to the human animal as well. But very few men will be found voluntarily to diminish the amount of their breakfast or dinner because on that day or on the following day they are going to stay in the house instead of engaging in vigorous outdoor labor.

No discussion on foods would be complete without a repetition of the frequently given warning, against fried meats and vegetables. Frying coats the outside of the food with a layer of fat not easily penetrated by the digestive juice and not acted on in the stomach. Therefore, all fried food, unless thoroughly chewed and then only when the frying is done in very hot fat so that it remains on the outside of the whole piece, will pass through the stomach without being acted upon. Frying is a quicker process than roasting, an advantage which appeals to the American notion of haste, but it is better to begin the preparation of the meal earlier and cook the meat by roasting or stewing and the vegetables by boiling or baking rather than to postpone the preparation of the meal until ten minutes before the hour and then fry everything.

Muscular and psychic reactions.

Another factor in the power of the body to utilize the food values is the condition of the body at the time of the meal. If the individual is exhausted or even tired, no complete digestion is possible, and particularly is this true if the exercise has involved excessive perspiration. So in hot weather, a heavy meal should not be eaten until after a half hour's rest and after copious water drinking to compensate for that loss of perspiration.

Studies on the digestion of foods and on other matters pertaining thereto have shown that the smell of food, or the mere suggestion of food, stimulates the organs for the production of the digestive juices. It is directly and literally correct, therefore, to say that one's mouth waters for this or that food because the thought or anticipation of the food, if pleasant, will actually cause the saliva to form and flow in the mouth. This is true of the other digestive juices as well, so that an appetizing fritter, for instance, showing the rich, brown crust will stir up the bile, and when the fried cake reaches the opening into the intestine, the bile will be there ready to act. This has been demonstrated by putting into the stomach of sleeping dogs various kinds of foods and finding that no digestive juices whatever were produced, although with the dog awake and seeing the food before eating, the juices began to flow in the usual fashion.

It follows, then, that the enjoyment of food is quite as important as any other digestive function, and on the contrary, the eating of all sorts of foods with no interest or attention is the best way to induce subsequent indigestion. The fact, then, that a business man eating at a quick-lunch counter does not get the full enjoyment and benefit from his meal as compared with those who sit leisurely over a well-appointed table does not result altogether from the difference in the viands, but rather in the different attitude toward the meal. It would undoubtedly be a great gain in every household if more attention could be given to a cheerful intercourse at meal times—not for the better relationship which would follow, but merely for the effect on the digestion.

After meals, violent exercise is not desirable because thereby vitality is taken away from the muscles of the stomach and intestines and is used up in the other muscles; but it is vigorous exercise after heavy meals only that is condemned, since moderate exercise after ordinary meals is not objectionable. Nor is there any evidence, unless the meal has been excessive, that mental exercise after a meal does any harm. The amount of mental tissue used up in the ordinary processes of mental work is not great enough to call for any large diminution of the supply of blood to other parts of the body.

Consumption of water.

A move in the right direction to-day undoubtedly is the tendency to increase the quantity of water to drink. The body is nine-tenths per cent water, and while a large part of the water in the tissues is made chemically by combinations of hydrogen and oxygen, there must be a constant replenishing of the liquids of the body.

The ordinary person ought to drink, or consume with his food in some way, at least two quarts of water a day, and many difficulties with the liver, kidneys, and other organs would be avoided if this amount of water daily were imbibed. Probably the contention that water should not be taken at meals is not particularly tenable except as the continual swallowing of water increases the tendency to swallow food without chewing, a childish habit sure to lead to distress later. But, to eat one's dinner or part of one's dinner and then drink a glass of water cannot reasonably be assumed to interfere with any digestive process. It is quite likely, in fact, that the greater dilution of the mass in the stomach will tend to easier absorption later on.

Condiments and drinks.

There are certain kinds of foods which, though not strictly included in the four elements of food already named, yet are so common as to deserve special mention. Chief among these are the condiments and drinks, particularly coffee and tea. So far as the nutritive value of such materials as salt and pepper, vinegar or spices, goes, they are practically negligible, and yet, undoubtedly, these flavors play an important part in the suggestion of pleasure and therefore in the excitement leading to the excretion of the digestive juices. If one ate salt pork and boiled potatoes always, eating would be a tiresome affair, and it is quite likely that such a sameness of food would fail to excite subsequent digestion, merely from the monotony of the affair. Salt, however, has a particular rÔle in that the human body craves this mineral, and, while its exact value in the body is not clearly known, a certain amount of it must always be provided. The wild tribes of Africa, for instance, away from deposits of salt consider it their most valuable possession and will go to great lengths to procure it. Animals, in the same way, go great distances for a supply of salt.

Coffee and tea are generally consumed merely for the pleasure which the warm drink gives. Both, however, have a certain stimulating effect on the nervous system, and when a tired woman refuses food but drinks cup after cup of strong tea, the exhilarating effect can be produced only at the expense of nerves and muscular tissue which must be later atoned for. Similarly, when a man under stress drinks strong black coffee to keep up, he must pay the penalty for the stimulant. The natural forces of the human body are able to do normally a certain amount of work, their ability to perform this work being directly proportioned to the energy derived from the food-supply taken into the body.

No amount of tea, coffee, or alcohol will add to the living tissue of the system; it merely goads the nerves and muscles to further action, however tired and unwilling they may be. When the stimulant is stopped, or after a time in spite of the stimulant, the exhausted nerves and muscles refuse to continue, and the depleted body stops work and may even die. A certain amount of stimulants at infrequent intervals for particular occasions may do no harm, but the pity of it is that the habit once started, the ultimate effects are forgotten in the apparent relief of the moment. In the case of tea, besides the stimulating effect, a certain substance known as tannin is developed, particularly when the tea is boiled, and this substance is really harmful on account of its strong astringent property, which acts injuriously on the membrane of the stomach. The bitter taste of the tannin is disguised when milk is used with the tea, and it has been pointed out that tea used without milk or cream is safer than tea with milk, because without the milk the bitter taste would prevent the tea being boiled so long.

Alcohol is stimulating in its nature, because of its setting free from their usual control by the will the unconscious elements of the brain; while the effect of alcohol on the system as a whole is, as has been carefully proved by scientific investigation, unfortunate in every respect. Whether the alcohol be in the form of whisky or brandy or gin or in such milder forms as wines, beers, and hard cider, the continued use of even a small quantity acts adversely on the memory, on the will, on the intellect, on the inventive power, and on all the mental processes. It has a deteriorating effect on all the muscular tissue throughout the body, and while this is sufficiently deplorable, its effect on the mind is by far the more serious. No idea is more false than that a small amount of alcohol aids in the performance of work of any sort, and experience in the army, navy, and in exploring expeditions all go to show that the use of alcohol in any form reduces the capacity, both for activity and endurance. As a protection against cold, it is worse than useless, and the feeling of warmth which drinking alcohol in any form produces, does not manufacture heat in the body, but is rather a source of danger on account of the reaction of the whole system.

Tobacco.

The use of tobacco may or may not be injurious to the human system, and it is said by those accustomed to its use that it is for them a source of great enjoyment and comfort. The essential poison of tobacco is known as nicotine, and experiments are very readily made with this substance, extracted from the plant, to show its deadly character on the heart and nerve cells of animals. It is easy to demonstrate that the use of tobacco affects the heart, since the common "out-of-breath feeling" which comes to users of tobacco when climbing hills or running is well known. No young man training for an athletic event would think of smoking, on account of the danger to his wind.

No boy should smoke, because nothing should be allowed to interfere with the fullest development of the heart and nervous system, and without question tobacco is a potent factor in influencing both. In many individual cases it has been shown that the use of tobacco in excess has a bad effect on digestion, while in other cases the trembling hand and inattentive mind indicate the result on the nervous system. No general law or rule can be laid down, and each man must act as his own individual constitution seems to require.

The drug habit.

The use of drugs is, in some cases, so persistent and leads to such dire results that it is well worth while to enter a protest against such practices. The poor creatures who have become fast victims of the morphine habit or the opium habit or the cocaine habit, or of any one of a dozen which might be named, will not be affected by anything that may be said here. But a word of warning may serve to restrain those who are only at the beginning of this downward path of which the end is positive and certain. The use of drugs once begun is sure to increase until, stupefied by their action, the victim becomes a sot, unfitted for work and a burden to himself, his relatives, and his friends.

Not less dangerous is the use of so-called patent medicines. In most cases, patent medicines are swindles, pure and simple, containing no remedial ingredients and acting only as stimulants. An advertisement some time since, which claimed to cure not only tuberculosis but also cancer, falling of the womb, hair, or eyelids, insanity, epilepsy, drunkenness, disorderly conduct, and pimples was printed in many newspapers. This remarkable remedy was found by analysis to contain ninety-nine parts of water to one part of harmless salts. Many of the vaunted remedies contain morphine or alcohol in such large quantities as to be dangerous, the more so because their presence is not suspected. Such remedies as Dr. Bull's Cough Syrup, Boschees German Sirup, Dr. King's New Discovery for Consumption, Shiloh's Consumptive Cure, Piso's Consumptive Cure, Peruna, Duffy's Malt Whisky, Warner's Safe Cure, and Paine's Celery Compound are all by analysis said to contain large amounts of morphine, chloroform, or alcohol.

Consumptives cannot be cured by any drug now known, and any person who believes it is mistaken. Cancer still baffles the skill of the most clever and the best-trained scientists. It is perfect folly to believe that any drug or man can cure either disease by a few pills or by a few bottles of medicine. The wise man or woman will avoid patent medicines unless they carry their formula on their label and unless they are prescribed by some reputable physician.