The Woods Hutchinson Health Series
A HANDBOOK OF HEALTH
WOODS HUTCHINSON, A. M., M. D.
Sometime Professor of Anatomy, University of Iowa; Professor of Comparative Pathology and Methods of Science Teaching, University of Buffalo; Lecturer, London Medical Graduates' College and University of London; and State Health Officer of Oregon. Author of "Preventable Diseases," "Conquest of Consumption," "Instinct and Health," etc.
Houghton Mifflin Company Boston New York Chicago Copyright, 1911, by Woods Hutchinson All Rights Reserved Tenth Impression
Looking upon the human body from the physical point of view as the most perfect, most ingeniously economical, and most beautiful of living machines, the author has attempted to write a little handbook of practical instruction for the running of it.
And seeing that, like other machines, it derives the whole of its energy from its fuel, the subject of foods—their properties, uses, and methods of preparation—has been gone into with unusual care. An adequate supply of clean-burning food-fuel for the human engine is so absolutely fundamental both for health and for efficiency—we are so literally what we have eaten—that to be well fed is in very fact two-thirds of the battle of life from a physiological point of view. The whole discussion is in accord with the aim, kept in view throughout the book, of making its suggestion and advice positive instead of negative, pointing out that, in the language of the old swordsman, "attack is the best defense." If we actively do those things that make for health and efficiency, and which, for the most part, are attractive and agreeable to our natural instincts and unspoiled tastes,—such as exercising in the open air, eating three square meals a day of real food, getting nine or ten hours of undisturbed sleep, taking plenty of fresh air and cold water both inside and out,—this will of itself carry us safely past all the forbidden side paths without the need of so much as a glance at the "Don't" and "Must not" with which it has been the custom to border and fence in the path of right living.
On the other hand, while fully alive to the undesirability, and indeed wickedness, of putting ideas of dread and suffering into children's minds unnecessarily, yet so much of the misery in the world is due to ignorance, and could have been avoided if knowledge of the simplest character had been given at the proper time, that it has been thought best to set forth the facts as to the causation and nature of the commonest diseases, and the methods by which they may be avoided. This is peculiarly necessary from the fact that most of the gravest enemies of mankind have come into existence within a comparatively recent period of the history of life,—only since the beginning of civilization, in fact,—so that we have as yet developed no natural instincts for their avoidance.
Nor do we admit that we are adding anything to the stock of fears in the minds of children—the nurse-maid and the bad boys in the next alley have been ahead of us in this respect. The child-mind is too often already filled with fears and superstitions of every sort, passed down from antiquity. Modern sanitarians have been accused of merely substituting one fear for another in the mind of the child—bacilli instead of bogies. But, even if this be true, there are profound and practical differences between the two terrors. One is real, and the other imaginary. A child cannot avoid meeting a bacillus; he will never actually make the acquaintance of a bogie. Children, like savages and ignorant adults, believe and invent and retail among themselves the most extraordinary and grotesque theories about the structure and functions of their bodies, the nature and causation of their illnesses and aches and pains. A plain and straightforward statement of the actual facts about these things not only will not shock or repel them, or make them old before their time, but, on the contrary, will interest them greatly, relieve their minds of many unfounded dreads, and save them from the commonest and most hurtful mistakes of humanity—those that are committed through ignorance.
I. RUNNING THE HUMAN AUTOMOBILE 1
II. WHY WE HAVE A STOMACH 4 What Keeps Us Alive 4 The Digestive System 7 The Journey down the Food Tube 9
III. THE FOOD-FUEL OF THE BODY-ENGINE 21 What Kind of Food should We Eat? 21 The Three Great Classes of Food-Fuel 25
IV. THE COAL FOODS 27 Proteins, or "Meats" 27
V. THE COAL FOODS (Continued) 40 Starches 40 Sugars 48
VI. THE COAL FOODS (Continued) 51 Animal Fats 51 Nuts 55
VII. KINDLING AND PAPER FOODS—FRUITS AND VEGETABLES 56
VIII. COOKING 62
IX. OUR DRINK 69 Filling the Boiler of the Body-Engine 69 Where our Drinking Water Comes from 72 Causes and Dangers of Polluted Water 75 Methods of Obtaining Pure Water 81 Home Methods of Purifying Water 87
X. BEVERAGES, ALCOHOL, AND TOBACCO 89 Alcohol 93 Tobacco 103
XI. THE HEART-PUMP AND ITS PIPE-LINE SYSTEM 108 The Blood Vessels 108 The Heart 115
XII. THE CARE OF THE HEART-PUMP AND ITS PIPE LINES 120
XIII. HOW AND WHY WE BREATHE 130
XIV. HOW TO KEEP THE LUNG-BELLOWS IN GOOD CONDITION 139 The Need of Pure Air 139 Colds, Consumption, and Pneumonia 152 How to Conquer Consumption 156 Pneumonia 165
XV. THE SKIN 167 Our Wonderful Coat 167 The Glands in the Skin 170 The Nails 172 The Blood-Mesh of the Skin 174 The Nerves in the Skin 177
XVI. HOW TO KEEP THE SKIN HEALTHY 179 Clothing 179 Baths and Bathing 184 Care of the Nails 188 Diseases and Disturbances of the Skin 189
XVII. THE PLUMBING AND SEWERING OF THE BODY 196
XVIII. THE MUSCLES 202
XIX. THE STIFFENING RODS OF THE BODY-MACHINE 210
XX. OUR TELEPHONE EXCHANGE AND ITS CABLES 216
XXI. THE HYGIENE OF BONES, NERVES, AND MUSCLES 228 How to Get and Keep a Good Figure 228 Our Feet 230 Sleep and Rest 232 Disorders of Muscles and Bones 233 Troubles of the Nervous System 235
XXII. EXERCISE AND GROWTH 241
XXIII. THE LOOKOUT DEPARTMENT 252 The Nose 253 The Tongue 257 The Eye 259 The Ear 266 Our Spirit-Levels 269
XXIV. THE SPEECH ORGANS 271
XXV. THE TEETH, THE IVORY KEEPERS OF THE GATE 277
XXVI. INFECTIONS, AND HOW TO AVOID THEM 286
XXVII. ACCIDENTS AND EMERGENCIES 314
QUESTIONS AND EXERCISES 331
GLOSSARY AND INDEX 343
PAGE TO ATTEMPT TO RUN AN AUTOMOBILE WITHOUT KNOWING HOW WOULD BE REGARDED AS FOOLHARDY 2
WHERE SUN-POWER IS MADE INTO FOOD FOR US 6
THE FOOD ROUTE IN THE DIGESTIVE SYSTEM 8
THE SALIVARY GLANDS 10
A SECTION OF THE LINING SURFACE OF THE STOMACH 14
A LONGITUDINAL SECTION OF STOMACH, OR PEPTIC, GLANDS 15
A CHEAP HOME-MADE ICE BOX 23
A BABY-MILK STATION 30
CLEAN, DRY SUNNING YARDS AT A MODEL DAIRY 33
CLEANLINESS BEFORE MILKING 34
THE MILKING HOUR AT A MODEL DAIRY 35
MILKING BY VACUUM PROCESS 36
WASHING THE BOTTLES AT A MODEL DAIRY 37
BACTERIA IN CLEAN AND IN DIRTY MILK 38
DANGER FROM DIPPED MILK 38
MILK INSPECTION AT THE RETAIL STORE 39
A THOROUGH BAKING, AND A VALUABLE CRUST 44
AN IDEAL BAKERY WITH LIGHT, AIR, AND CLEANLINESS 45
A BASEMENT BAKERY—A MENACE TO THE PUBLIC HEALTH 46
CANDY, LIKE OTHER FOODS, SHOULD BE CLEAN 50
A SMALL STORE, CLEANLY AND HONEST 54
THE JOY OF HIS OWN GARDEN PATCH 61
THE KITCHEN SHOULD BE CARED FOR AS ONE OF THE MOST IMPORTANT ROOMS IN THE HOUSE 63
A KNOWLEDGE OF COOKING IS A VALUABLE PART OF A GOOD EDUCATION 66
BOYS, AS WELL AS GIRLS, SHOULD KNOW HOW TO COOK 67
THE CHAINED CUP 71
THE SPOUTING FOUNTAIN 72
NATURE'S FILTER-BED 74
AN EXAMPLE OF GOOD FARM DRAINAGE 76
THE DANGER SPOT ON THE FARM 78
TYPHOID EPIDEMIC IN THE MOHAWK-HUDSON VALLEY 80
ARTESIAN WELL BORINGS 82
A CITY WATER SUPPLY BROUGHT FROM THE FAR HILLS 84
A RESERVOIR AND COSTLY DAM 86
SCRAPING THE SEDIMENT FROM THE BOTTOM OF A RESERVOIR 87
THE DOMESTIC FILTER IN USE 88
A MILK STATION IN A CITY PARK 92
PROPORTION OF ALCOHOL IN LIGHT WINE, IN BEER, IN WHISKEY 95
A BOARD OF HEALTH EXAMINATION FOR WORKING PAPERS 105
A TEST OF CLEAR HEAD AND STEADY NERVES 106
BLOOD CORPUSCLES 109
SURFACE VEINS AND DEEP-LYING ARTERIES OF INNER SIDE OF RIGHT ARM AND HAND 112
DIAGRAM OF ARTERY, CAPILLARIES, AND VEIN 114
THE EXTERIOR OF THE HEART 116
DIAGRAM OF VALVES IN THE VEINS AND HEART 117
THE BLOOD-ROUTE TROUGHT THE HEART 118
THE SCHOOL PHYSICIAN EXAMINING HEART AND LUNGS 121
ROWING IS A SPLENDID EXERCISE FOR HEART AND LUNGS 127
THE GREAT ESSENTIAL TO LIFE—AIR 131
DIAGRAM OF THE AIR TUBES AND LUNGS 134
"IMPROVING THEIR WIND" 137
THE "DARK ROOM" DANGER OF THE TENEMENTS 145
VENTILATING THE PUPILS, AS WELL AS THE CLASSROOM 146
A WELL-AIRED CLASSROOM 147
A HEALTHFUL ARRANGEMENT OF WINDOWS AND SHADES 148
A HEALTHFUL BEDROOM 151
DISEASE GERMS 152
A VACUUM CLEANER 153
EXERCISE IN THE COLD IS A GOOD PREVENTIVE OF COLDS 155
A YEAR OF CONSUMPTION ON MANHATTAN ISLAND 156
CONSUMPTION IN CHICAGO 157
A REPORT-FORM FROM A HEALTH DEPARTMENT LABORATORY 159
A SIGN THAT OUGHT NOT TO BE NECESSARY 160
A COMPARATIVE DEATH-RATE FROM CONTAGIOUS DISEASES 161
A TUBERCULOSIS TENT COLONY IN WINTER 163
AN OUTDOOR CLASSROOM FOR TUBERCULOUS CHILDREN 165
THE LAYERS OF THE SKIN 169
THE GLANDS IN THE SKIN 171
RESULTS OF TIGHT CLOTHING 181
A COMFORTABLE DRESS FOR OUTDOOR STUDY IN COLD WEATHER 183
AS A TONIC, SWIMMING IS THE BEST FORM OF BATHING 185
THE URINARY SYSTEM 200
THE MUSCLE-SHEET 205
USE OF MUSCLES IN BOWLING 206
USE OF MUSCLES IN FOOTBALL 207
PATELLA AND MUSCLE 207
THE HUMAN SKELETON 211
THE SPINAL COLUMN 212
A BALL-AND-SOCKET JOINT 213
A HINGE JOINT 213
LENGTHWISE SECTION OF BONE 214
CROSS SECTION OF BONE 214
THE NERVOUS SYSTEM 218
THE POSITION OF THE BODY IS AN INDEX TO ITS HEALTH 229
IMPRINT OF (1) ARCHED FOOT AND (2) FLAT FOOT 230
THE RESULT OF WEARING A FASHIONABLE SHOE 231
CALLUS FORMED AROUND A FRACTURE 234
A TRAINED BODY 242
TUG OF WAR 245
THE GIANT STRIDE 246
SCHOOL GARDENING 248
A WASTED CHANCE FOR PUBLIC HEALTH 249
AN OBSTACLE RACE 250
THE HIGH JUMP 251
THE APPARATUS OF VISION 260
A SCHOOL EYE-TEST 263
DISINFECTING A BABY'S EYES AT BIRTH 265
THE APPARATUS OF HEARING 267
THE VOCAL CORDS 272
TEETH—A QUESTION OF CARE 278
A TOOTH 279
THE REPLACING OF THE MILK TEETH 282
A TOOTH-BRUSH DRILL 284
THE WINNING FIGHT 290
DEATH-RATE FROM MEASLES 291
DEATH-RATE FROM DIPHTHERIA AND CROUP 294
BILL OF HEALTH 298
GERMS OF MALARIA 301
OILING A BREEDING GROUND OF MOSQUITOES 304
AN EDUCATIONAL FLY POSTER 310
A BREEDING PLACE OF FLIES AND FILTH 311
A TOURNIQUET 321
POISON IVY 325
THE NEW METHOD OF ARTIFICIAL BREATHING 328
PLATES IN COLOR
DIAGRAM OF THE CIRCULATORY SYSTEM facing 110
DIAGRAM SHOWING GENERAL PLAN AND POSITION OF BODY-MACHINERY facing 198
A HANDBOOK OF HEALTH
RUNNING THE HUMAN AUTOMOBILE
The Body-Automobile. If you were to start to-morrow morning on a long-distance ride in an automobile, the first thing that you would do would be to find out just how that automobile was built; how often it must have fresh gasoline; how its different speed gears were worked; what its tires were made of; how to mend them; and how to cure engine troubles. To attempt to run an automobile, for even a ten-mile ride, with less information than this, would be regarded as foolhardy.
Yet most of us are willing to set out upon the journey of life in the most complicated, most ingenious, and most delicate machine ever made—our body—with no more knowledge of its structure than can be gained from gazing in the looking-glass; or of its needs, than a preference for filling up its fuel tank three times a day. More knowledge than this is often regarded as both unnecessary and unpleasant. Yet there are few things more important, more vital to our health, our happiness, and our success in life, than to know how to steer and how to road-repair our body-automobile. This we can learn only from physiology and hygiene.
The General Plan of the Human Automobile is Simple. Complicated as our body-automobile looks to be, there are certain things about the plan and general build of it which are plain enough. It has a head end, where fuel supplies are taken in and where its lamps and other look-out apparatus are carried; a body in which the fuel is stored and turned into work or speed, and into which air is drawn to help combustion and to cool the engine pipes. It has a pair of fore-wheels (the arms) and a pair of hind-wheels (the legs), though these have been reduced to only one spoke each, and swing only about a quarter of the way around and back again when running, instead of round and round. It has a steering gear (the brain), just back of the headlights, and a system of nerve electric wires connecting all parts of it. It gets warm when it runs, and stops if it is not fed.
There is not an unnecessary part, or unreasonable "cog," anywhere in the whole of our bodies. It is true that there are a few little remnants which are not quite so useful as they once were, and which sometimes cause trouble. But for the most part, all we have to do is to look long and carefully enough at any organ or part of our bodies, to be able to puzzle out just what it is or was intended to do, and why it has the shape and size it has.
Why the Study of Physiology is Easy. There is one thing that helps to make the study of physiology quite easy. It is that you already know a good deal about your body, because you have had to live with it for a number of years past, and you can hardly have helped becoming somewhat acquainted with it during this time.
You have, also, another advantage, which will help you in this study. While your ideas of how to take care of your body are rather vague, and some of them wrong, most of them are in the main right, or at least lead you in the right direction. You all know enough to eat when you are hungry and to drink when you are thirsty, even though you don't always know when to stop, or just what to eat. You like sunny days better than cloudy ones, and would much rather breathe fresh air than foul. You like to go wading and swimming when you are hot and dusty, and you don't need to be told to go to sleep when you are tired. You would much rather have sugar than vinegar, sweet milk than sour milk; and you dislike to eat or drink anything that looks dirty or foul, or smells bad.
These inborn likes and dislikes—which we call instincts—are the forces which have built up this wonderful body-machine of ours in the past and, if properly understood and trained, can be largely trusted to run it in the future. How to follow these instincts intelligently, where to check them, where to encourage them, how to keep the proper balance between them, how to live long and be useful and happy—this is what the interesting study of physiology and hygiene will teach you.
WHY WE HAVE A STOMACH
WHAT KEEPS US ALIVE
The Energy in Food and Fuel. The first question that arises in our mind on looking at an engine or machine of any sort is, What makes it go? If we can succeed in getting an answer to the question, What makes the human automobile go? we shall have the key to half its secrets at once. It is fuel, of course; but what kind of fuel? How does the body take it in, how does it burn it, and how does it use the energy or power stored up in it to run the body-engine?
Man is a bread-and-butter-motor. The fuel of the automobile is gasoline, and the fuel of the man-motor we call food. The two kinds of fuel do not taste or smell much alike; but they are alike in that they both have what we call energy, or power, stored up in them, and will, when set fire to, burn, or explode, and give off this power in the shape of heat, or explosions, which will do work.
Food and Fuel are the Result of Life. Fuels and foods are also alike in another respect; and that is, that, no matter how much they may differ in appearance and form, they are practically all the result of life. This is clear enough as regards our foods, which are usually the seeds, fruits, and leaves of plants, and the flesh of animals. It is also true of the cord-wood and logs that we burn in our stoves and fireplaces. But what of coal and gasoline? They are minerals, and they come, as we know, out of the depths of the earth. Yet they too are the product of life; for the layers of coal, which lie sixty, eighty, one hundred and fifty feet below the surface of the earth, are the fossilized remains of great forests and jungles, which were buried millions of years ago, and whose leaves and branches and trunks have been pressed and baked into coal. Gasoline comes from coal oil, or petroleum, and is simply the "juice" which was squeezed out of these layers of trees and ferns while they were being crushed and pressed into coal.
How the Sun is Turned into Energy by Plants and Animals. Where did the flowers and fruits and leaves that we now see, and the trees and ferns that grew millions of years ago, get this power, part of which made them grow and part of which was stored away in their leaves and branches and seeds? From the one place that is the source of all the force and energy and power in this world, the sun.
That is why plants will, as you know, flourish and grow strong and green only in the sunlight, and why they wilt and turn pale in the dark. When the plant grows, it is simply sucking up through the green stuff (chlorophyll) in its leaves the heat and light of the sun and turning it to its own uses. Then this sunlight, which has been absorbed by plants and built up into their leaves, branches, and fruits, and stored away in them as energy or power, is eaten by animals; and they in turn use it to grow and move about with.
Plants can use this sun-power only to grow with and to carry out a few very limited movements, such as turning to face the sun, reaching over toward the light, and so on. But animals, taking this power at second-hand from plants by eating their leaves or fruits, can use it not merely to grow with, but also to run, to fight, to climb, to cry out, and to carry out all those movements and processes which we call life.
Plants, on the other hand, are quite independent of animals; for they can take up, or drink, this sun-power directly, with the addition of water from the soil sucked up through their roots, and certain salts melted in it. Plants can live, as we say, upon non-living foods. But animals must take their supply of sun-power at second-hand by eating the leaves and the fruits and the seeds of plants; or at third-hand by eating other animals.
All living things, including ourselves, are simply bundles of sunlight, done up in the form of cabbages, cows, and kings; and so it is quite right to say that a healthy, happy child has a "sunny" disposition.
Plants and Animals Differ in their Way of Taking Food. As plants take in their sun-food and their air directly through their leaves, and their drink of salty water through their roots, they need no special opening for the purpose of eating and drinking, like a mouth; or place for storing food, like a stomach. They have mouths and stomachs all over them, in the form of tiny pores on their leaves, and hair-like tubes sticking out from their roots. They can eat with every inch of their growing surface.
But animals, that have to take their sun-food or nourishment at second-hand, in the form of solid pieces of seeds, fruits, or leaves of plants, and must take their drink in gulps, instead of soaking it up all over their surface, must have some sort of intake opening, or mouth, somewhere on the surface; and some sort of pouch, or stomach, inside the body, in which their food can be stored and digested, or melted down. By this means they also get rid of the necessity of staying rooted in one place, to suck up moisture and food from the soil. One of the chief and most striking differences between plants and animals is that animals have mouths and stomachs, while plants have not.
THE DIGESTIVE SYSTEM
How the Food Reaches the Stomach. Our body, then, has an opening, which we call the mouth, through which our food-fuel can be taken in. A straight delivery tube, called the gullet, or esophagus, runs down from the mouth to a bag, or pouch, called the stomach, in which the food is stored until it can be used to give energy to the body, just as the gasoline is stored in the automobile tank until it can be burned.
The mouth opening is furnished with lips to open and close it and assist in picking up our food and in sucking up our drink; and, as much of our food is in solid form, and as the stomach can take care only of fluid and pulpy materials, nature has provided a mill in the mouth in the form of two arches, of semicircles, of teeth, which grind against each other and crush the food into a pulp.
In the bottom or floor of the mouth, there has grown up a movable bundle of muscles, called the tongue, which acts as a sort of waiter, handing the food about the mouth, pushing it between the teeth, licking it out of the pouches of the cheeks to bring it back into the teeth-mill again, and finally, after it has been reduced to a pulp, gathering it up into a little ball, or bolus, and shooting it back down the throat, through the gullet, into the stomach.
The Intestines. When the food has been sufficiently melted and partially digested in the stomach, it is pushed on into a long tube called the intestine, or bowel. During its passage through this part of the food tube, it is taken up into the veins, and carried to the heart. From here it is pumped all over the body to feed and nourish the millions of little cells of which the body is built. This bowel tube, or intestine, which, on account of its length, is arranged in coils, finally delivers the undigested remains of the food into a somewhat larger tube called the large intestine, in the lower and back part of the body, where its remaining moisture is sucked out of it, and its solid waste material passed out of the body through the rectum in the form of the feces.
THE JOURNEY DOWN THE FOOD TUBE
The Flow of Saliva and "Appetite Juice." We are now ready to start some food-fuel, say a piece of bread, on its journey down our food tube, or alimentary canal. One would naturally suppose that the process of digestion would not begin until the food got well between our teeth; but, as a matter of fact, it begins before it enters our lips, or even before it leaves the table. If bread be toasted or freshly baked, the mere smell of it will start our mouths to watering; nay, even the mere sight of food, as in a pastry cook's window, with the glass between us and it, will start up this preparation for the feast.
This flow of saliva in the mouth is of great assistance in moistening the bread while we are chewing it; but it goes farther than this. Some of the saliva is swallowed before we begin to eat; and this goes down into the stomach and brings word to the juices there to be ready, for something is coming. As the food approaches the mouth, a message also is telegraphed down the nerves to the stomach, which at once actively sets to work pouring out a digestive juice in readiness, called the "appetite juice." This shows how important are, not merely a good appetite, but also attractive appearance and flavor in our food; for if this appetite juice is not secreted, the food may lie in the stomach for hours before the proper process of digestion, or melting, begins.
The Salivary Glands. Now, where does this saliva in the mouth come from? It is poured out from the pouches of the cheeks, and from under the tongue, by some little living sponges, or juice factories, known as salivary glands.
All the juices poured out by these glands, indeed nearly all the fluids or juices in our bodies, are either acid or alkaline. By acid we mean sour, or sharp, like vinegar, lemon juice, vitriol (sulphuric acid), and carbonic acid (which forms the bubbles in and gives the sharp taste to plain soda-water). By alkaline we mean "soap-like" or flat, like soda, lye, lime, and soaps of all sorts. If you pour an acid and an alkali together—like vinegar and soda—they will "fizz" or effervesce, and at the same time neutralize or "kill" each other.
The Use of the Saliva. As the chief purpose of digestion is to prepare the food so that it will dissolve in water, and then be taken up by the cells lining the food-tube, the saliva, like the rest of the body juices, consists chiefly of water. Nothing is more disagreeable than to try to chew some dry food—like a large, crisp soda cracker, for instance—which takes more moisture than the salivary glands are able to pour out on such short notice. You soon begin to feel as if you would choke unless you could get a drink of water. But it is not altogether advisable to take this short cut to relief, because the salivary juice contains what the drink of water does not—a ferment, or digestive substance (ptyalin), which possesses the power of turning the starch in our food into sugar. As starch is only very slowly soluble, or "meltable," in water, while sugar is very readily so, the saliva is of great assistance in the process of melting, known as digestion. The changing of the starch to sugar is the reason why bread or cracker, after it has been well chewed, begins to taste sweetish.
This change in the mouth, however, is not of such great importance as we at one time thought, because even with careful mastication, a certain amount of starch will be swallowed unchanged. Nature has provided for this by causing another gland farther down the canal, just beyond the stomach, called the pancreas, to pour into the food tube a juice which is far stronger in sugar-making power than the saliva, and this will readily deal with any starch which may have escaped this change in the mouth. Moreover, this "sugaring" of starch goes on in the stomach for twenty to forty minutes after the food has been swallowed.
Starchy foods, like bread, biscuit, crackers, cake, and pastry, are really the only ones which require such thorough and elaborate chewing as we sometimes hear urged. Other kinds of food, like meat and eggs—which contain no starch and consequently are not acted upon by the saliva—need be chewed only sufficiently long and thoroughly to break them up and reduce them to a coarse pulp, so that they can be readily acted upon by the acid juice of the stomach.
Down the Gullet. When the food has been thoroughly moistened and crushed in the mouth and rolled into a lump, or bolus, at the back of the tongue, it is started down the elevator shaft which we call the gullet, or esophagus. It does not fall of its own weight, like coal down a chute, but each separate swallow is carried down the whole nine inches of the gullet by a wave of muscular action. So powerful and closely applied is this muscular pressure that jugglers can train themselves, with practice, to swallow standing on their heads and even to drink a glass of water in that position; while a horse or a cow always drinks "up-hill." This driving power of the food tube extends throughout its entire length; it is carried out by a series of circular rings of muscles, which are bound together by other threads of muscle running lengthwise, together forming the so-called muscular coat of the tube. By contracting, or squeezing down in rapid succession, one after another, they move the food along through the tube. The failure of these little muscles to act properly is one of the causes of constipation and biliousness. Sometimes the action of the muscles is reversed, and then we get a gush of acid, or bitter, half-digested food up into the mouth, which we call "heart-burn" or "water-brash."
The Stomach—its Shape, Position, and Size. By means of muscular contraction, then, the gullet-elevator carries the food into the stomach. This is a comparatively simple affair, merely a ballooning out, or swelling, of the food tube, like the bulb of a syringe, making a pouch, where the food can be stored between meals, and where it can undergo a certain kind of melting or dissolving. This pouch is about the shape of a pear, with its larger end upward and pointing to the left, and its smaller end tapering down into the intestine, or bowel, on the right, just under the liver. The middle part of the stomach lies almost directly under what we call the "pit of the stomach," though far the larger part of it lies above and to the left of this point, going right up under the ribs until it almost touches the heart, the diaphragm only coming between. This is one of the reasons why, when we have an attack of indigestion, and the stomach is distended with gas, we are quite likely to have palpitation and shortness of breath as well, because the gas-swollen left end of the stomach is pressing upward against the diaphragm and thus upon the heart and the lungs. Most cases of imagined heart trouble are really due to indigestion.
The Lining Surface of the Stomach. Now let us look more carefully at the lining surface of the stomach, for it is very wonderful. Like all other living surfaces, it consists of tiny, living units, or "body bricks" called cells, packed closely side by side like bricks in a pavement. We speak of the mucous membrane, or lining, of our food tube, as if it were one continuous sheet, like a piece of calico or silk; but we must never forget that it is made up of living ranks of millions of tiny cells standing shoulder to shoulder.
These cells are always actively at work picking out the substances they need, and manufacturing out of them the ferments and acids, or alkalies, needed for acting upon the food in their particular part of the tube, whether it be the mouth, the stomach, or the small intestine.
The Peptic Juice. The cells of the stomach glands manufacture and pour out a slightly sour, or acid, juice containing a ferment called pepsin. The acid, which is known as hydrochloric acid, and the pepsin together are able to melt down pieces of meat, egg, or curds of milk, and dissolve them into a clear, jelly-like fluid, or thin soup, which can readily be absorbed by the cells lining the intestine.
You can see now why you shouldn't take large doses of soda or other alkalies, just because you feel a little uncomfortable after eating. They will make your stomach less acid and perhaps relieve the discomfort, but they stop or slow down digestion. Neither is it well to swallow large quantities of ice-water, or other very cold drinks, at meal times, or during the process of digestion. As digestion is largely getting the food dissolved in water, the drinking of moderate quantities of water, or other fluids, at meals is not only no hindrance, but rather a help in the process. The danger comes only when the drink is taken so cold as to check digestion, or when it is used to wash down the food in chunks, before it has been properly ground by the teeth.
Digestion in the Stomach. Although usually a single, pear-shaped pouch, the stomach, during digestion, is practically divided into two parts by the shortening, or closing down, of a ring of circular muscle fibres about four inches from the lower end, throwing it into a large, rounded pouch on the left, and a small, cone-shaped one on the right. The gullet, of course, opens into the large left-hand pouch; and here the food is stored as it is swallowed until it has become sufficiently melted and acidified (mixed with acid juice) to be ready to pass on into the smaller pouch. Here more acid juice is poured out into it, and it is churned by the muscles in the walls of the stomach until it is changed to a jelly-like substance.
Digestion in the Small Intestine. The food-pulp now passes on into the small intestine, where it is acted upon by two other digestive juices—the bile, which comes from the liver, and the pancreatic juice, which is secreted by the pancreas.
The liver and the pancreas are a pair of large glands which have budded out, one on each side of the food tube, about six inches below where the food enters the small intestine from the stomach. The liver weighs nearly three pounds, and the pancreas about a quarter of a pound.
Of these two glands, the pancreas, though the smaller, is far more important in digestion. In fact, it is the most powerful digestive gland in the body. Its juice, the pancreatic juice, can do everything that any other digestive juice can, and do it better. It contains a ferment for turning starch into sugar, which is far more powerful than that of the saliva; also another (trypsin), which will dissolve meat-stuffs nearly twice as fast as the pepsin of the stomach can; and still another, not possessed by either mouth or stomach glands, which will melt fat, so that it can be sucked up by the lining cells of the intestine.
What does this great combination of powers in the pancreas mean? It means that we have now reached the real centre and chief seat of digestion, namely, the small intestine, or upper bowel. This is where the food is really absorbed, taken up into the blood, and distributed to the body. All changes before this have been merely preparatory; all after it are simply a picking up of the pieces that remain.
In general appearance, this division of the food tube is very simple—merely a tube about twenty feet long and an inch in diameter, thrown into coils, so as to pack into small space, and slung up to the backbone by broad loops of a delicate tissue (mesentery). It looks not unlike twenty feet of pink garden hose.
The intestine also is provided with glands that pour out a juice known as the intestinal juice, which, although not very active in digestion, helps to melt down still further some of the sugars, and helps to prevent putrefaction, or decay, of the food from the bacteria which swarm in this part of the tube.
By the time the food has gone a third of the way down the small intestine, a good share of the starches in it have been turned into sugar and absorbed by the blood vessels in its wall; and the meats, milk, eggs, and similar foods have been digested in the same way.
There still remains the bulk of the fats to be disposed of. These fats are attacked by the pancreatic juice and the bile, and made ready for digestion. Like other foods, they are then eaten by the cells of the intestinal wall; but instead of going directly into the blood vessels, as the sugars and other food substances do, they are passed on into another set of little tubes or vessels, called the lymphatics. In these they are carried through the lymph glands of the abdomen into the great lymph duct, which finally pours them into one of the great veins not far from the heart. Tiny, branching lymphatic tubes are found all over the body, picking up what the cells leave of the fluid which has seeped out of the arteries for their use and returning it to the veins through the great lymph duct.
All these different food substances, in the process of digestion, do not simply soak through the lining cells of the food tube, as through a blotting paper or straining cloth, but are actually eaten by the cells and very much changed in the process, and are then passed through the other side of the cells, either into the blood vessels of the wall of the intestine or into the lymph vessels, practically ready for use by the living tissues of the body. It is in the cells then that our food is turned into blood, and it is there that what we have eaten becomes really a part of us. It may even be said that we are living upon the leavings of the little cell citizens that line our food tube; but they are wonderfully decent, devoted little comrades of the rest of our body cells, and generous in the amount of food they pass on to the blood vessels.
As the food-pulp is squeezed on from one coil to another through the intestine, it naturally has more and more of its nourishing matter sucked out of it; until, by the time it reaches the last loop of the twenty feet of the small intestine, it has lost over two-thirds of its food value.
The Final Stage—the Journey through the Large Intestine. From the small intestine what remains of the food-pulp is poured into the last section of the food tube, which enlarges to from two to three inches in diameter. It is known as the large intestine, or large bowel. This section is only about five feet long. The first three-fourths of it is called the colon; the last or lowest quarter, the rectum, the discharge-pipe of the food tube. The principal use of the colon is to suck out the remaining traces of nourishing matter from the food and the water in which it is dissolved, thus gradually drying the food-pulp down to a solid or pasty form, in which condition it collects in a large "S" shaped loop of the bowel just above the rectum, until discharged.
The Waste Materials. By the time that the remains of the food-pulp have reached the middle of the large intestine, they have lost all their nutritive value and most of their water. All the way down from the upper part of the small intestine they have been receiving solid waste substances poured out by the glands of the intestines; indeed, the bulk of the feces is made up of these intestinal secretions, not, as is generally supposed, of the undigested remains of the food. Ninety-five per cent of our food is absorbed; the body-engine burns up its fuel very clean. The next largest part of the feces is bacteria, or germs; and the third and smallest, the indigestible fragments and remainders of food, such as vegetable fibres, bran, fruit skins, pits, seeds, etc. Hence the feces are not only worthless from a food point of view, but full of all sorts of possibilities for harm; and the principal interest of the body lies in getting rid of them as promptly and regularly as possible.
It can easily be seen how important it is that a habit should be formed, which nothing should be allowed to break, of promptly and regularly getting rid of these waste materials. For most persons, once in twenty-four hours is normal; for some, twice or even three times in the day. Whatever interval is natural, it should be attended to, beginning at a fixed hour every morning.
Constipation, and how to Prevent It. Constipation should not be treated by the all too common method of swallowing salts, which will cause a flood of watery matters to be poured through the food tube and sluice it clean of both poisons and melting food at the same time, leaving it in an exhausted and disturbed condition afterwards; nor by taking some irritating vegetable cathartic, generally in the form of pills, which sets up a violent action of the muscles of the food tube, driving its contents through at headlong speed; nor by washing out the lower two or three feet of the bowel with injections of water; although any or all of these may be resorted to occasionally for temporary relief. A very large portion of the food eaten is sucked out of the food tube into the blood vessels, passes through a large area of the body, and is poured out again as waste through the glands of the lining of the lower third of the bowel. Constipation, therefore, is caused by disturbances which interfere with these processes all over the body, not only in the stomach and bowels. Its only real and permanent cure is through exercise in the open air, sleep, and proper ventilation of bedrooms, with abundance of nourishing food, including plenty of green vegetables and fresh fruits.
The Appendix and Appendicitis. The beginning of the large bowel, where the small bowel empties into it, is the largest part of it, and forms a curious pouch called the cecum, or "blind" pouch. From one side of this projects a little wormlike tube, twisted and coiled upon itself, from three to six inches long and of about the size of a slate pencil. This is the famous appendix vermiformis (meaning, "wormlike tag"), which is such a frequent source of trouble. It is the shrunken and shriveled remains of a large pouch of the intestine which once opened into the cecum, and was used originally as a sort of second stomach for delaying and digesting the remains of the food. The reason why it gives rise to so much trouble is that it is so small—scarcely larger than will admit a knitting-needle—and so twisted upon itself that germs or other poisonous substances swallowed with the food may get into it, start a swelling or inflammation, get trapped in there by the closing of the narrow mouth of the tube, and form an abscess, which leaks through, or bursts into, the cavity of the body, called the peritoneum. This causes a very serious and often fatal blood poisoning.
Fortunately, appendicitis, or inflammation of the appendix, is not a very common disease, causing only one in one hundred of all deaths that occur; and these are mostly cases that were not treated promptly. Yet, if you have a severe, constant pain, rather low down in the right-hand corner of your abdomen, and if, when you press your hand firmly down in that corner, it hurts, or you feel a lump, it is decidedly safest to call a doctor and let him see what the condition really is, and advise you what to do.
 The term salts includes, as will be explained later, a large number of substances, like ordinary table salt, baking soda, and the laxative salts.
 There are three pairs of these: one just below the ears and behind the angles of the jaw, known as the parotid; one under the middle of the lower jaw known as the submaxillary; and a small pair just under the tip of the tongue, called the sublingual. These glands have grown up from the very simplest of beginnings. At first there was just a little pocketing or pouching down of the mucous lining, like the finger of a glove; then a couple of smaller hollow fingers budded off from the bottom of the first finger; then four smaller fingers from the bottom of these; and so on, until a regular little hollow tree or shrub of these tiny tubes was built up, all discharging through the original hollow stem, which has now become what we call the duct of the gland. Every secreting gland in the body—the stomach (or peptic) glands, the salivary glands, the liver, the pancreas—is built up upon this simple plan. The saliva and the juice of the pancreas and that of the liver (bile) are alkaline, as are also the blood and most juices of the body. The stomach juice is acid, as also are the urine and the perspiration.
 It is wonderfully elastic and constantly changing in size, contracting till it will scarcely hold a quart when empty, and expanding, as food or drink is put into it, until it will easily hold two quarts, or even a gallon or more when greatly distended, as by gas.
 If you take some pepsin which has been extracted from the stomach of a pig or a calf, melt it in water in a glass tube, then drop one or two little pieces of meat or hard-boiled white of egg into it, you can see them slowly melt away like sugar in a cup of coffee. If you add a few drops of hydrochloric acid, the melting will go on much faster; and if you warm up the tube to about the heat of the body, it will proceed faster still. So nature knew just what she was doing when she provided pepsin and acid and warmth in the stomach.
 The liver and the bile are more fully described in chapter XVII.
 Tiny plant cells, known also as germs, which cause fermentation, decay, and many diseases.
THE FOOD-FUEL OF THE BODY-ENGINE
WHAT KIND OF FOOD SHOULD WE EAT?
Generally speaking, our Appetites will Guide us. Our whole body is an ingenious machine for catching food, digesting it, and turning the energy, or fuel value, which it contains, into life, movement, and growth.
Naturally, two things follow: first, that the kind and amount of food which we eat is of great importance; and second, that from the millions of years of experience that the human body has had in trying all sorts of foods, it has adapted itself to certain kinds of food and developed certain likes and dislikes which we call appetites. Those who happened to like unhealthy and unwholesome foods were poisoned, or grew thin and weak and died off, so that we are descended solely from people who had sound and reliable food appetites; and, in the main, what our instincts and appetites tell us about food is to be depended upon.
The main questions which we have to consider are: How much of the different kinds of food it is best for us to eat, and in what proportions we should use them. Both men and animals, since the world began, have been trying to eat and digest almost everything that they could get into their mouths. And what we now like and prepare as foods are the things which have stood the test, and proved themselves able to yield strength and nourishment to the body. So practically every food that comes upon our tables has some kind of real food value, or it wouldn't appear there.
The most careful study and analysis have shown that almost every known food has some peculiar advantage, such as digestibility, or cheapness, or pleasant taste as flavoring for other more nutritious, but less interesting, foods. But some foods have much higher degrees of nutritiousness or digestibility or wholesomeness than others; so that our problem is to pick out from a number of foods that "taste good" to us, those which are the most nutritious, the most digestible, and the most wholesome, and to see that we get plenty of them. It is not that certain foods, or classes of food, are "good," and should be eaten to the exclusion of all others; nor that certain foods, or classes of food, are "bad," and should be excluded from our tables entirely; but that certain foods are more nutritious, or more wholesome, than others; and that it is best to see that we get plenty of the former before indulging our appetites upon the latter.
Beware of Tainted Food. The most dangerous fault that any food can have is that it shall be tainted, or spoiled, or smell bad. Spoiling, or tainting, means that the food has become infected by some germs of putrefaction, generally bacteria or moulds (see chapter XXVI). It is the poisons—called ptomaines, or toxins—produced by these germs which cause the serious disturbances in the stomach, and not either the amount or the kind of food itself. Even a regular "gorge" upon early apples or watermelon or cake or ice cream will not give you half so bad, nor so dangerous, colic as one little piece of tainted meat or fish or egg, or one cupful of dirty milk, or a single helping of cabbage or tomatoes that have begun to spoil, or of jam made out of spoiled berries or other fruit. This spoiling can be prevented by strict cleanliness in handling foods, especially milk, meat, and fruit; by keeping foods screened from dust and flies; and by keeping them cool with ice in summer time, thus checking the growth of these "spoiling" germs. The refrigerator in the kitchen prevents colic or diarrhea, ice in hot weather is one of the necessaries of life. Smell every piece of food to be eaten, in the kitchen before it is cooked, if possible; but if not, at the table avoid everything that has an unpleasant odor, or tastes queer, and you will avoid two-thirds of the colic, diarrhea, and bilious attacks which are so often supposed to be due to eating too much.
Variety in Food is Necessary. Man has always lived on, and apparently required, a great variety of foods, animal and vegetable—fish and flesh, nuts, fruit, grains, fat, sugar, and vegetables. Indeed, it was probably because man could live on anything and everything that he was able to survive in famines and to get so far ahead of all other sorts of animals.
We still need a great variety of different sorts of food in order to keep our health; so our tendency to become tired of a certain food, after we have had it over and over and over again, for breakfast, dinner, and supper, is a sound and healthy one. There is no "best food"; nor is there any one food on which we can live and work, as an engine will work all its "life" on one kind of coal, wood, or oil. No one kind of food contains all the stuffs that our body is made of and needs, in exactly the right proportions. It takes a dozen or more different kinds of food to supply these, and the body picks out what it wants, and throws away the remainder.
Even the best and most nutritious and digestible single food, like meat, or bread and butter, or sugar, is not sufficient by itself; nor will it do for every meal in the day, or every day in the week. We must eat other things with it; and we must from time to time change it for something which may even be not quite so nutritious, in order to give our body the opportunity to select from a great variety of foods the particular things which its wonderful instincts and skill can use to build it up and keep it healthy. This is why every grocery store, every butcher shop, every fish market, and every confectioner's shows such a great variety of different kinds of foods put up and prepared in all sorts of ways. Although nearly two-thirds of the actual fuel which we put into our body-boilers is in the form of a dozen or fifteen great staple foods, like bread, meat, butter, sugar, eggs, milk, potatoes, and fish, yet all the lighter foods, also, are needed for perfect health.
It is possible, by careful selection, and by taking a great deal of trouble, to supply all the elements of the body from animal foods alone, or from vegetable foods alone. But practically, it has everywhere, and in all ages, been found that the best and most healthful diet is a proper combination of animal and vegetable foods. Our starches, for instance, which furnish most of our fuel,—though they give us comparatively little to build up, or repair, the body with,—are found, as we have seen, in the vegetable kingdom, in grains and fruits; while most of our proteins and fats, which chiefly give us the materials with which to build up, or repair, the body, are found in the animal kingdom. There is no advantage whatever in trying to exclude either animal food or vegetable food from our dietary. Both animal and vegetable foods are wholesome in their proper place, and their proper place is on the table together.
Those nations which live solely, or even chiefly, upon one or two kinds of staple foods, such as rice, potatoes, corn-meal, or yams, do so solely because they are too poor to afford other kinds of food, or too lazy, or too uncivilized, to get them; and instead of being healthier and longer-lived than civilized races, they are much more subject to disease and live only about half as long.
THE THREE GREAT CLASSES OF FOOD-FUEL
Food is Fuel. Now what is the chief quality which makes one kind of food preferable to another? As our body machine runs entirely upon the energy or "strength" which it gets out of its food, a good food must have plenty of fuel value; that is to say, it must be capable of burning and giving off heat and steaming-power. Other things being equal, the more it has of this fuel value, the more desirable and valuable it will be as a food.
From this point of view, foods may be roughly classified, after the fashion of the materials needed to build a fire in a grate or stove, as Coal foods, Kindling foods, and Paper foods. Although coal, kindling, and paper are of very different fuel values, they are all necessary to start the fire in the grate and to keep it burning properly. Moreover, any one of them would keep a fire going alone, after a fashion, provided that you had a grate or furnace large enough to burn it in, and could shovel it in fast enough; and the same is true, to a certain degree, of the foods in the body.
How to Judge the Fuel Value of Foods. One of the best ways of roughly determining whether a given food belongs in the Coal, the Kindling, or the Paper class, is to take a handful or spoonful of it, dry it thoroughly by some means,—evaporating, or driving off the water,—and then throw what is left into a fire and see how it will burn. A piece of beef, for instance, would shrink a good deal in drying; but about one-third of it would be left, and this dried beef would burn quite briskly and would last for some time in the fire. A piece of bread of the same size would not shrink so much, but would lose about the same proportion of its weight; and it also would burn with a clear, hot flame, though not quite so long as the beef. A piece of fat of the same size would shrink very little in drying and would burn with a bright, hot flame, nearly twice as long as either the beef or the bread. These would all be classed as Coal foods.
Then if we were to dry a slice of apple, it would shrink down into a little leathery shaving; and this, when thrown into the fire, would burn with a smudgy kind of flame, give off very little heat, and soon smoulder away. A piece of raw potato of the same size would shrink even more, but would give a hotter and cleaner flame. A leaf of cabbage, or a piece of beet-root, or four or five large strawberries would shrivel away in the drying almost to nothing and, if thoroughly dried, would disappear in a flash when thrown on the fire. These, then, except the potato, we should regard as Kindling foods.
But it would take a large handful of lettuce leaves, or a big cup of beef-tea, or a good-sized bowl of soup, or a big cucumber, or a gallon of tea or coffee, to leave sufficient solid remains when completely dried, to make more than a flash when thrown into the fire. These, then, are Paper foods, with little fuel value.
THE COAL FOODS
Kinds of Coal Foods. There are many different kinds of Coal foods, such as pork, mutton, beef, bread, corn-cakes, bacon, potatoes, rice, sugar, cheese, butter, and so on. But when you come to look at them more closely, and to take them to pieces, or, as we say, analyze them, you will see that they all fall into three different kinds or classes: (1) Proteins, such as meat, milk, fish, eggs, cheese, etc. (2) Starch-sugars (carbohydrates), found pure as laundry starch and as white sugar; also found, as starch, making up the bulk of wheat and other grains, and of potatoes, rice, peas; also found, as sugar, in honey, beet-roots, sugar cane, and the sap of maple trees. (3) Fats, found in fat meats, butter, oil, nuts, beeswax, etc.
This whole class of Coal foods can be recognized by the fact that usually some one of them will form the staple, or main dish, of almost any regular meal, which is generally a combination of all three classes—a protein in the shape of meat; a starch-sugar in the form of bread, potatoes, or rice; and a fat in the form of butter in northern climates, or of olive oil in the tropics.
PROTEINS, OR "MEATS"
Proteins, the "First Foods." There are proteins, or "meats," both animal and vegetable; and no one can support life without protein in some form. This is because proteins alone contain sufficient amounts of the great element called nitrogen, which forms a large part of every portion of our bodies. This is why they are called proteins, meaning "first foods," or most necessary foods. Whatever we may live on in later life, we all began on a diet of liquid meat (milk), and could have survived and grown up on nothing else.
Composition of Proteins. Nearly all our meats are the muscle of different sorts of animals, made of a soft, reddish, animal pulp called myosin; the other principal proteins being white of egg, curd of milk, and a gummy, whitish-gray substance called gluten, found in wheat flour. This gluten is the stuff that makes the paste and dough of wheat flour sticky, so that you can paste things together with it; while that made from corn meal or oatmeal will fall to pieces when you take it up. The jelly-like or pulp-like myosin in meat is held together by strings or threads of tough, fibrous stuff; and the more there is of this fibrous material in a particular piece or "cut," of meat, the tougher and less juicy it is. The thick, soft muscles, which lie close under the backbone in the small of the back, in all animals, have less of this tough and indigestible fibrous stuff in them, and cuts across them give us the well-known porter-house, sirloin, or tenderloin steaks, and the best and tenderest mutton and pork chops.
Fuel Value of Meats. Weight for weight, most of the butcher's meats—beef, pork, mutton, and veal—have about the same food value, differing chiefly in the amount of fat that is mixed in with their fibres, and in certain flavoring substances, which give them, when roasted, or broiled, their special flavors. The different flavors are not of any practical importance, except in the case of mutton, which some people dislike and therefore can take only occasionally, and in small amounts.
The amount of fat in meats, however, is more important; and depends largely upon how well the animal has been fed. There is usually the least amount of fat in mutton, more in beef, and by far the greatest amount in pork. This fat adds to the fuel value of meat, but makes it a little slower of digestion; and its presence in large amounts in pork, together with the fact that it lies, not only in layers and streaks, but also mixed in between the fibres of the lean as well has caused this meat to be regarded as richer and more difficult of digestion than either beef or mutton. This, however is not quite fair to the pork, because smaller amounts of it will satisfy the appetite and furnish the body with sufficient fuel and nutrition. If it be eaten in moderate amounts and thoroughly chewed, it is a wholesome and valuable food.
Veal is slightly less digestible than beef or mutton, on account of the amount of slippery gelatin in and among its fibres; but if well cooked and well chewed, it is wholesome.
The other meats—chicken, duck, and other poultry, game, etc.—are of much less nutritive value than either beef, pork, or mutton, partly because of the large amount of waste in them, in the form of bones, skin, and tendons, and partly from the greater amount of water in them. But their flavors make them an agreeable change from the staple meats.
Fish belongs in the same class as poultry and consists of the same muscle substance, but, as you can readily see by the way that it shrinks when dried, contains far more water and has less fuel value. Some of the richer and more solid fishes, like salmon, halibut, and mackerel, contain, in addition to their protein, considerable amounts of fat and, when dried or cured, give a rather high fuel value at moderate cost. But the peculiar flavor of fish, its large percentage of water, and the special make-up of its protein, give it a very low food value, and render it, on the whole, undesirable as a permanent staple food. Races and classes who live on it as their chief meat-food are not so vigorous or so healthy as those who eat also the flesh of animals. As a rule, it is not best to use fish as the main dish of a meal oftener than two or three times a week.
Milk. Milk is an interesting food of great value because it combines in itself all three of the great classes of food-stuffs,—protein, starch-sugar, and fat. Its protein is a substance called casein, which forms the bulk of curds, and which, when dried and salted, is called cheese. The fat is present in little tiny globules which give milk its whitish or milky color. When milk is allowed to stand, these globules of fat, being lighter, float up to the top and form a layer which is called cream. When this cream is skimmed off and put into a churn, and shaken or beaten violently so as to break the little film with which each of these droplets is coated, they run together and form a yellow mass which we call butter. In addition to the curd and fat, milk contains also sugar, called milk-sugar (lactose), which gives it its sweetish taste. And as a considerable part of the casein, or curd, is composed of another starch-like body, or animal starch, this makes milk quite rich in the starch-sugar group of food-stuffs.
All these substances, of course, in milk are dissolved in a large amount of water, so that when milk is evaporated, or dried, it shrinks down to barely one-sixth of its former bulk. It is, in fact, a liquid meat, starch-sugar, and fat in one; and that is why babies are able to live and thrive on it alone for the first six months of their lives. It is also a very valuable food for older children, though, naturally, it is not "strong" enough and needs to be combined with bread, puddings, meat, and fat.
Soups and Broths. Soups, broths, and beef teas are water in which meats, bones, and other scraps have been boiled. They are about ninety-eight per cent water, and contain nothing of the meat or bones except some of their flavor, and a little gelatin. They have little or no nutritive or fuel value, and are really Paper foods, useful solely as stimulants to appetite and digestion, enabling us to swallow with relish large pieces of bread or crackers, or the potatoes, rice, pea-meal, cheese, or other real foods with which they are thickened. Their food value has been greatly exaggerated, and many an unfortunate invalid has literally starved on them. Ninety-five per cent of the food value of the meat and bones, out of which soups are made, remains at the bottom of the pot, after the soup has been poured off. The commercial extracts of meat are little better than frauds, for they contain practically nothing but flavoring matters.
Protein in Vegetables. Several vegetable substances contain considerable amounts of protein. One of these has already been mentioned,—the gluten or sticky part of bread,—and this is what has given wheat its well-deserved reputation as the best of all grains out of which to make flour for human food.
There is also another vegetable protein, called legumin, found in quite large amounts in dried beans and peas; but this is of limited food value, first because it is difficult of digestion, and secondly because with it, in dried peas and beans, are found a pungent oil and a bitter substance, which give them their peculiar strong flavor, both of which are quite irritating to the average person's digestion. So distressing and disturbing are these flavoring substances to the civilized stomach, that, after thousands of attempts to use them more largely, it has been found that a full meal of beans once or twice a week is all that the comfort and health of the body will stand. This is really a great pity, for beans and peas are both nourishing and cheap. Nuts also contain much protein, but are both difficult of digestion and expensive.
Virtues and Drawbacks of Meats. Taken all together, the proteins, or meats, are the most nutritious and wholesome single class of foods. Their chief drawback is their expense, which, in proportion to their fuel value, is greater than that of the starches. Then, on account of their attractiveness, they may be eaten at times in too large amounts. They are also somewhat more difficult to keep and preserve than are either the starches or the fats. The old idea that, when burned up in the body, they give rise to waste products, which are either more poisonous or more difficult to get rid of than those of vegetable foods, is now regarded as having no sufficient foundation. Neither is the common belief that meats cause gout well founded.
The greatest danger connected with meats is that they may become tainted, or begin to spoil, or decay, before they are used. Unfortunately, the ingenious cook has invented a great many ways of smothering, or disguising, the well-marked bad taste of decayed, or spoiled, meat by spices, onions, and savory herbs. So, as a general thing, the safest plan, especially when traveling or living away from home, is to avoid as far as possible hashes, stews, and other "made" dishes containing meat. This is one of the ways in which spices and onions have got such a bad reputation for "heating the blood," or upsetting the stomach, when it is really the decayed meat which they are used to disguise that causes the trouble. Highly spiced dishes rob you of the services of your best guide to the wholesomeness of food—your nose.
Risks of Dirty Milk. The risks from tainting or spoiling are particularly great in the case of milk, partly on account of the dusty and otherwise uncleanly barns and sheds in which it is often handled and kept, and from which it is loaded with a heavy crop of bacteria at the very start; and partly because the same delicateness which makes it so easily digestible for babies, makes it equally easy for germs and bacteria to grow in it and spoil, or sour, it. You all know how disagreeable the taste of spoiled milk is; and it is as dangerous as it is disagreeable. A very large share of the illnesses of babies and young children, particularly the diseases of stomach and bowels which are so common in hot weather, are due to the use of spoiled, dirty milk.
There is one sure preventive for all these dangers, and that is absolute cleanliness from cow to customer. All the changes that take place in milk are caused by germs of various sorts, usually floating in the air, that get into it. If the milk is so handled and protected, from cow to breakfast table, that these germs cannot get into it, it will remain sweet for several days.
Boards of Health all over the world now are insisting upon absolutely clean barns and cleanly methods of handling, shipping, and selling milk. In most of our large cities, milk-men are not allowed to sell milk without a license; and this license is granted only after a thorough examination of their cattle, barns, and milk-houses. These clean methods of handling milk cost very little; they take only time and pains.
Nowadays, in the best dairies, it is required that the barns or sheds in which cows are milked shall have tight walls and roofs and good flooring; that the walls and roofs shall be kept white-washed; and the floor be cleaned and washed before each milking, so that no germs from dust or manure can float into the milk. Then the cows are kept in a clean pasture, or dry, graveled yard, instead of a muddy barnyard; and are either brushed, or washed down with a hose before each milking, so that no dust or dirt will fall from them into the milk. The men who are to milk wash their hands thoroughly with soap and water, and put on clean white canvas or cotton overalls, jackets, and caps. As soon as the milk has been drawn into the pails, it is carried into the milk-room and cooled down to a temperature of about forty-two degrees—that is, about ten degrees above freezing point. This is to prevent the growth of such few germs as may have got into it, in spite of all the care that has been taken. Then the milk is drawn into bottles; and the bottles are tightly capped by a water-proof pasteboard disc, or cover, which is not removed until the milk is brought into the house and poured into the glass, or cup, for use.
Milk handled like this costs from two to four cents a quart more to produce than when drawn from a cow smeared with manure, in a dark, dirty, strong-smelling barn, by a milker with greasy clothing and dirty hands; and then ladled out into pitchers in the open street, giving all the dust and flies that happen to be in the neighborhood a chance to get into it! But it is doubly worth the extra price, because, besides escaping stomach and bowel troubles, you get more cream and higher food value. There is one-third more food value in clean milk than in dirty milk, because its casein and sugar have not been spoiled and eaten by swarms of bacteria. How great a difference careful cleanliness of this sort can make in milk is shown by the difference in the number of bacteria that the two kinds of milk contain. Ordinary milk bought from the wagons in the open street, or from the cans in the stores, will contain anywhere from a million to a million and a half bacteria to the cubic centimeter (about fifteen drops); and samples have actually been taken and counted, which showed five and six millions.
Such a splendid food for germs is milk, and so rapidly do they grow in it, that dirty milk will actually contain more of them to the cubic inch than sewage, as it flows in the sewers. Now see what a difference a little cleanliness will make! Good, clean, carefully handled milk, instead of having a million, or a million and a half, bacteria, will have less than ten thousand; and very clean milk may contain as low as three or four hundred, and these of harmless sorts. The whole gospel of the care of milk can be summed up in two sentences: (1) Keep dirt and germs out of the milk. (2) Keep the milk cool.
Besides the germs of the summer diseases of children, which kill more than fifty thousand babies every year in the United States, dirty milk may also contain typhoid germs and consumption germs. The typhoid germs do not come from the body of the cow, but get into the milk through its being handled by people who have, or have just recovered from, typhoid, or who are nursing patients sick with typhoid, and who have not properly washed their hands; or from washing the cans, or from watering the milk with water taken from a well or stream infected with typhoid. It is estimated that about one-eighth of all the half million cases of typhoid that occur in the United States every year are carried through dirty milk.
The germs of consumption, or tuberculosis, that are present in milk may come from a cow that has the disease; or from consumptive human beings who handle the milk; or from the dust of streets or houses—which often contains disease germs. The latter sources are far the more dangerous; for, as is now pretty generally agreed, although the tuberculosis of cattle can be given to human beings, it is not very actively dangerous to them; and probably not more than three or four per cent of all cases of tuberculosis come from this source. The idea, however, of allowing the milk of cows diseased from any cause to be used for human food, is not to be tolerated for a moment. All good dairymen and energetic Boards of Health now insist upon dairy herds being tested for tuberculosis, and the killing, or weeding out, of all cows that show they have the disease.
Cheese. Cheese is the curd of milk squeezed dry of its liquid (whey), salted, pressed into a mould, and allowed to ferment slowly, or "ripen," in which process a considerable part of its casein is turned into fat. It is a cheap, concentrated, and very nutritious food, and in small amounts is quite appetizing. But unfortunately, the acids and extracts which have formed in the process of fermentation and ripening are so irritating to the stomach, that it can usually be eaten only in small amounts, without upsetting the digestion. Its chief value is as a relish with bread, crackers, potatoes, or macaroni. In moderate amounts, it is not only appetizing and digestible, but will assist in the digestion of other foods; hence the custom of eating a small piece of "ripe" cheese at the end of a heavy meal.
THE COAL FOODS (Continued)
Sources of Starch. The starches are valuable and wholesome foods. They form the largest part, both in bulk and in fuel value, of our diet, and have done so ever since man learned how to cultivate the soil and grow crops of grain. The reason is clear: One acre of good land will grow from ten to fifteen times the amount of food in the form of starch in grains or roots, as of meat in the shape of cattle or sheep. Consequently, starch is far cheaper, and this is its great advantage.
Our chief supply of starch is obtained from the seed of certain most useful grasses, which we call wheat, oats, barley, rye, rice, and corn, and from the so-called "roots" of the potato. Potatoes are really underground buds packed with starch, and their proper name is tubers.
Starch, when pure or extracted, is a soft, white powder, which you have often seen as cornstarch, or laundry starch. As found in grains, it is mixed with a certain amount of vegetable fibre, covered with husks, or skin, and has the little germ or budlet of the coming plant inside it. It has been manufactured and laid down by little cells inside their own bodies, which make up the grains; so that each particular grain of starch is surrounded by a delicate husk—the wall of the cell that made it. This means that grains and other starch foods have to be prepared for eating by grinding and cooking. The grinding crushes the grains into a powder so that the starch can be sifted out from the husks and coating of the grain, and the fibres which hold it together; and the cooking causes the tiny starch grain to swell and burst the cell wall, or bag, which surrounds it.
Starches as Fuel. The starches contain no nitrogen except a mere trace in the framework of the grains or roots they grow in. They burn very clean; that is, almost the whole of them is turned into carbon dioxid gas and water.
This burning quality makes the starches a capital fuel both in the body and out of it. You may have heard of how settlers out on the prairies, who were a long way from a railroad and had no wood or coal, but plenty of corn, would fill their coal scuttles with corn and burn that in their stoves; and a very bright, hot fire it made.
One of the chief weaknesses of the starches is that they burn up too fast, so that you get hungry again much more quickly after a meal made entirely upon starchy foods, like bread, crackers, potatoes, or rice, than you do after one which has contained some meat, particularly fat, which burns and digests more slowly.
How Starch is Changed into Sugar. As we learned in chapter II, the starches can be digested only after they are turned into sugars in the body. If you put salt with sugar or starch, although it will mix perfectly and give its taste to the mixture, neither the salt nor the starch nor the sugar will have changed at all, but will remain exactly as it was in the first place, except for being mixed with the other substances. But if you were to pour water containing an acid over the starch, and then boil it for a little time, your starch would entirely disappear, and something quite different take its place. This, when you tasted it, you would find was sweet; and, when the water was boiled off, it would turn out to be a sugar called glucose. Again, if you should pour a strong acid over sawdust, it would "char" it, or change it into another substance, carbon. In both of these cases—that of the starch and of the sawdust—what we call a chemical change would have taken place between the acid and the starch, and between the strong acid and the sawdust.
If we looked into the matter more closely, we should find that what has happened is that the starch and the sawdust have changed into quite different substances. Starches are insoluble in water; that is, although they can be softened and changed into a jelly-like substance, they cannot be completely melted, or dissolved, like salt or sugar. Sugar, on the other hand, is a perfectly soluble or "meltable" substance, and can soak or penetrate through any membrane or substance in the body. Therefore all the starches which we eat—bread, biscuit, potato, etc.—have to be acted upon by the ferments of our saliva and our pancreatic juice, and turned into sugar, called glucose, which can be easily poured into the blood and carried wherever it is needed, all over the body. Thus we see what a close relation there is between starch and sugar, and why the group we are studying is sometimes called the starch-sugars.
Wheat—our Most Valuable Starch Food. The principal forms in which starch comes upon our tables are meals and flours, and the various breads, cakes, mushes, and puddings made out of these. Far the most valuable and important of all is wheat flour, because this grain contains, as we have seen, not only starch, but a considerable amount of vegetable "meat," or gluten, which is easily digested in the stomach. This gluten, however, carries with it one disadvantage—its stickiness, or gumminess. The dough or paste made by mixing wheat flour with water is heavy and wet, or, as we say, "soggy," as compared with that made by mixing oatmeal or corn meal or rice flour with water. If it is baked in this form, it makes a well-flavored, but rather tough, leathery sort of crust; so those races that use no leavening, or rising-stuff, in their wheat bread, roll it out into very thin sheets and bake it on griddles or hot stones.
Most races that have wheat, however, have hit upon a plan for overcoming this heaviness and sogginess, and that is the rather ingenious one of mixing some substance in the dough which will give off bubbles of a gas, carbon dioxid, and cause it to puff up and become spongy and light, or, as we say, "full of air." This is what gives bread its well-known spongy or porous texture; but the tiny cells and holes in it are filled, not with air, but with carbon dioxid gas.
Making Bread with Yeast. There are several ways of lightening bread with carbon dioxid gas. The oldest and commonest is by mixing in with the flour and water a small amount of the frothy mass made by a germ, or microbe, known as yeast or the yeast plant. Then the dough is set away in a warm place "to rise," which means that the busy little yeast cells, eagerly attacking the rich supply of starchy food spread before them, and encouraged by the heat and moisture, multiply by millions and billions, and in the process of growing and multiplying, give off, like all other living cells, the gas, carbon dioxid. This bubbles and spreads all through the mass, the dough begins to rise, and finally swells right above the pan or crock in which it was set. If it is allowed to stand and rise too long, it becomes sour, because the yeast plant is forming, at the same time, three other substances—alcohol, lactic acid (which gives an acid taste to the bread), and vinegar. Usually they form in such trifling amounts as to be quite unnoticeable. When the bread has become light enough, it is put into the oven to be baked.
The baking serves the double purpose of cooking and thus making the starch appetizing, and of killing the yeast germs so that they will carry their fermentation no further. Bread that has not been thoroughly baked, if it is kept too long, will turn sour, because some of the yeast germs that have escaped will set to work again.
That part of the dough that lies on the surface of the loaf, and is exposed to the direct heat of the oven has its starch changed into a substance somewhat like sugar, known as dextrin, which, with the slight burning of the carbon, gives the outside, or crust, of bread its brownish color, its crispness, and its delicious taste. The crust is really the most nourishing part of the loaf, as well as the part that gives best exercise to the teeth.
Making Bread with Soda or Baking-Powders. Another method of giving lightness to bread is by mixing an acid like sour milk and an alkali like soda with the flour, and letting them effervesce and give off carbon dioxid. This is the mixture used in making the famous "soda biscuit." Still another method is by the use of baking-powders, which are made of a mixture of some cheap and harmless acid powder with an alkaline powder—usually some form of soda. As long as these powders are kept dry, they will not act upon each other; but as soon as they are moistened in the dough, they begin to give off carbon dioxid gas.
Neither sour milk and soda nor baking-powder will make as thoroughly light and spongy and digestible bread as will yeast. If, however, baking-powders are made of pure and harmless materials, used in proper proportions so as just to neutralize each other, and thus leave no excess of acid or alkali, and if the bread is baked very thoroughly, they make a wholesome and nutritious bread, which has the advantage of being very quickly and easily made. The chief objection to soda or baking-powder bread is that, being often made in a hurry, the acid and the alkali do not get thoroughly mixed all through the flour, and consequently do not raise or lighten the dough properly, and the loaf or biscuit is likely to be heavy and soggy in the centre. This heavy, soggy stuff can be neither properly chewed in the mouth, nor mixed with the digestive juices, and hence is difficult to digest. If, however, soda biscuits are made thin and baked thoroughly so as to make them at least half or two-thirds crust, they are perfectly digestible and wholesome, and furnish a valuable and appetizing variety for our breakfast and supper tables.
Bran or Brown Bread. Flour made by grinding the wheat-berry without sifting the husks, or bran, out of it is called "whole-wheat" meal; and bread made from it is the brown "bran bread" or "Graham bread." It was at one time supposed that because brown bread contained more nitrogen than white bread, it was more wholesome and nutritious, but this has been found to be a mistake, because the extra nitrogen in the brown bread is in the form of husks and fibres, which the stomach is quite unable to digest. Weight for weight, white bread is more nutritious than brown. The husks and fibres, however, which will not digest, pass on through the bowels unchanged and stir up the walls of the intestines to contract; hence they are useful in small quantities in helping to keep the bowels regular. But, like any other stimulus, too much of it will irritate and disturb the digestion, and cause diarrhea; so that it is not best to eat more than one-fifth of our total bread in the form of brown bread. Dyspeptics who live on brown bread, or on so-called "health foods," are simply feeding their dyspepsia.
"Breakfast Foods." The same defect exists in most of the breakfast cereals which flood our tables and decorate our bill-boards. Some of these are made of the waste of flouring mills, known as "middlings," "shorts," or bran, which were formerly used for cow-feed. The claims of many of them are greatly exaggerated, for they contain no more nourishment, or in no more digestible form, than the same weight of bread; and they cost from two to five times as much. As they come on our tables, they are nearly seven-eighths water; and the cream and sugar taken with them are of higher food value than they are. They should never be relied upon as the main part of a meal.
Corn Meal. Corn meal is one of the richest meals in nutritive value for its price, as it has an abundance of starch and a small amount of fat. It is, however, poor in nitrogen, and like the other grains, in countries where wheat will grow, it is chiefly valuable for furnishing cakes, fritters, and mushes to give variety to the diet, and help to regulate the bowels.
Oatmeal. Oatmeal comes the nearest to wheat in the amount of nitrogen or protein, but the digestible part of this is much smaller than in wheat, and the indigestible portion is decidedly irritating to the bowels, so that if used in excess of about one-fifth of our total starch-food required, it is likely to upset the digestion.
Rye. Rye also contains a considerable amount of gluten, but is much poorer in starch than wheat is; and the bread made out of its flour—the so-called "black bread" of France and Germany—is dark, sticky, and inclined to sour readily. Most of the "rye" bread sold in the shops, or served on our tables, is made of wheat flour with a moderate mixture of rye to give the sour taste.
Rice. Rice consists chiefly of starch, and makes nutritious puddings or cakes, and may be used as a vegetable, in the place of potatoes, with meat and fish. It is, however, lacking in flavor, and when properly cooked, contains so much water that it has to be eaten in very large amounts to furnish much nutrition.
Potatoes. The only important starchy food outside of the grains is potatoes. These contain considerable amounts of starch, but mixed with a good deal of cellulose, or vegetable fibre, and water, so that, like rice, large amounts of them must be eaten in order to furnish a good fuel supply. They, however, make a very necessary article of diet in connection with meats, fish, and other vegetables.
As a rough illustration of the fuel value of the different starch foods, it may be said that in order to get the amount of nourishment contained in an ordinary pound loaf of wheat or white bread, it would be necessary to eat about seven pounds of cooked rice, as it comes on the table; about twelve pounds of boiled potatoes; or a bowl of oatmeal porridge about the size of a wash-basin.
Where Sugar is Obtained. The other great member of the starch, or carbohydrate, group of foods is sugar. This is a scarcer and more expensive food than starch because, instead of being found in solid masses in grains and roots like starch, it is scattered, very thinly, through the fruits, stems, and roots of a hundred different plants, seldom being present in greater amounts than two or three per cent. It is, however, so valuable a food, with so high a fuel value, and is so rapidly digested and absorbed, that man has always had a very keen desire for it, or, as we say, a "sweet tooth," and has literally searched the whole vegetable kingdom the world over to discover plants from which it could be secured in larger amounts. During the last two hundred years it has been obtained chiefly from two great sources: the juicy stem of a tall, coarse reed, or cane, the sugar-cane, growing in the tropics; and (within the last fifty years) the sweet juice of the large root of a turnip-like plant, the beet. Another source of sugar, in the earlier days of this country, was the juice or sap of the sugar maple, which is still greatly relished as a luxury, chiefly in the form of syrup.
Honey is nearly pure sugar together with certain ferments and flavoring extracts, derived in part from the flowers from which it is gathered, and in part from the stomach, or crop, of the bee.
The Food Value of Sugar. In the early days of its use, sugar, on account of its expensiveness, was looked upon solely as a luxury, and used sparingly—either as a flavoring for less attractive foods, or as a special treat; and like most new foods, it was declared to be unwholesome and dangerous. But sugar is now recognized as one of our most useful and valuable foods. In fuel value, it is the equal, indeed the superior, weight for weight, of starch; and as all starch has to be changed into it before it can be used by the body, it is evident that sugar is more easily digested and absorbed than starch, and furnishes practically a ready-made fuel for our muscles.
How We should Use Sugar. The drawbacks of sugar are that, on account of its exceedingly attractive taste, we may eat too much of it; and that, because it is so satisfying, if we do eat too much of it either between meals or at the beginning of meals, our appetites will be "killed" before we have really eaten a sufficient supply of nourishing food. But all we have to do to avoid these dangers is to use common sense and a little self-control, without which any one of our appetites may lead us into trouble.
On account of this satisfying property, sugar is best eaten at, or near, the close of a meal; and taken at that time, there is no objection to its use nearly pure, as in the form of sweet-meats, or good wholesome candy. Its alleged injurious effects upon the teeth are largely imaginary and no greater than those of the starchy foods. The teeth of various tropical races which live almost entirely on sugar-cane during certain seasons of the year are among the finest in the world; and any danger may be entirely avoided by proper brushing and cleaning of the teeth and gums after eating.