"The lamp of life" is a very old metaphor for the mysterious principle vitalizing nerve and muscle; but no comparison could be so apt. The full-grown adult takes in each day, through lungs and mouth, about eight and a half pounds of dry food, water, and the air necessary for breathing purposes. Through the pores of the skin, the lungs, kidneys, and lower intestines, there is a corresponding waste; and both supply and waste amount in a year to one and a half tons, or three thousand pounds.
The steadiness and clear shining of the flame of a lamp depend upon quality, as well as amount of the oil supplied, and, too, the texture of the wick; and so all human life and work are equally made or marred by the food which sustains life, as well as the nature of the constitution receiving that food.
Before the nature and quality of food can be considered, we must know the constituents of the body to be fed, and something of the process through which digestion and nutrition are accomplished.
I shall take for granted that you have a fairly plain idea of the stomach and its dependences. Physiologies can always be had, and for minute details they must be referred to. Bear in mind one or two main points: that all food passes from the mouth to the stomach, an irregularly-shaped pouch or bag with an opening into the duodenum, and from thence into the larger intestine. From the mouth to the end of this intestine, the whole may be called the alimentary canal; a tube of varying size and some thirty-six feet in length. The mouth must be considered part of it, as it is in the mouth that digestion actually begins; all starchy foods depending upon the action of the saliva for genuine digestion, saliva having some strange power by which starch is converted into sugar. Swallowed whole, or placed directly in the stomach, such food passes through the body unchanged. Each division of the alimentary canal has its own distinct digestive juice, and I give them in the order in which they occur.
First, The saliva; secreted from the glands of the mouth:—alkaline, glairy, adhesive.
Second, The gastric juice; secreted in the inner or third lining of the stomach,—an acid, and powerful enough to dissolve all the fiber and albumen of flesh food.
Third, The pancreatic juice; secreted by the pancreas, which you know in animals as sweetbreads. This juice has a peculiar influence upon fats, which remain unchanged by saliva and gastric juice; and not until dissolved by pancreatic juice, and made into what chemists call an emulsion, can they be absorbed into the system.
Fourth, The bile; which no physiologist as yet thoroughly understands. We know its action, but hardly why it acts. It is a necessity, however; for if by disease the supply be cut off, an animal emaciates and soon dies.
Fifth, The intestinal juice; which has some properties like saliva, and is the last product of the digestive forces.
A meal, then, in its passage downward is first diluted and increased in bulk by a watery fluid which prepares all the starchy portion for absorption. Then comes a still more profuse fluid, dissolving all the meaty part. Then the fat is attended to by the stream of pancreatic juice, and at the same time the bile pours upon it, doing its own work in its own mysterious way; and last of all, lest any process should have been imperfect, the long canal sends out a juice having some of the properties of all.
Thus each day's requirements call for
Do not fancy this is all wasted or lost. Very far from it: for the whole process seems to be a second circulation, as it were; and, while the blood is moving in its wonderful passage through veins and arteries, another circulation as wonderful, an endless current going its unceasing round so long as life lasts, is also taking place. But without food the first would become impossible; and the quality of food, and its proper digestion, mean good or bad blood as the case may be. We must follow our mouthful of food, and see how this action takes place.
When the different juices have all done their work, the chyme, which is food as it passes from the stomach into the duodenum or passage to the lower stomach or bowels, becomes a milky substance called chyle, which moves slowly, pushed by numberless muscles along the bowel, which squeeze much of it into little glands at the back of the bowels. These are called the mesenteric glands; and, as each one receives its portion of chyle, a wonderful thing happens. About half of it is changed into small round bodies called corpuscles, and they float with the rest of the milky fluid through delicate pipes which take it to a sort of bag just in front of the spine. To this bag is fastened another pipe or tube—the thoracic duct—which follows the line of the spine; and up this tube the small bodies travel till they come to the neck and a spot where two veins meet. A door in one opens, and the transformation is complete. The small bodies are raw food no more, but blood, traveling fast to where it may be purified, and begin its endless round in the best condition. For, as you know, venous blood is still impure and dirty blood. Before it can be really alive it must pass through the veins to the right side of the heart, flow through into the upper chamber, then through another door or valve into the lower, where it is pumped out into the lungs. If these lungs are, as they should be, full of pure air, each corpuscle is so charged with oxygen, that the last speck of impurity is burned up, and it goes dancing and bounding on its way. That is what health means: perfect food made into perfect blood, and giving that sense of strength and exhilaration that we none of us know half as much about as we should. We get it sometimes on mountain-tops in clear autumn days when the air is like wine; but God meant it to be our daily portion, and this very despised knowledge of cookery is to bring it about. If a lung is imperfect, supplied only with foul air as among the very poor, or diseased as in consumption, food does not nourish, and you now know why. We have found that the purest air and the purest water contain the largest proportion of oxygen; and it is this that vitalizes both food and, through food, the blood.
To nourish this body, then, demands many elements; and to study these has been the joint work of chemists and physiologists, till at last every constituent of the body is known and classified. Many as these constituents are, they are all resolved into the simple elements, oxygen, hydrogen, nitrogen, and carbon, while a little sulphur, a little phosphorus, lime, chlorine, sodium, &c., are added.
FLESH and BLOOD are composed of water, fat, fibrine, albumen, gelatine, and the compounds of lime, phosphorus, soda, potash, magnesia, iron, &c.
BONE contains cartilage, gelatine, fat, and the salts of lime, magnesia, soda, &c., in combination with phosphoric and other acids.
CARTILAGE consists of chondrine, a substance somewhat like gelatine, and contains also the salts of sulphur, lime, soda, potash, phosphorus, magnesia, and iron.
BILE is made up of water, fat, resin, sugar, cholesterine, some fatty acids, and the salts of potash, iron, and soda.
THE BRAIN is made up of water, albumen, fat, phosphoric acid, osmazone, and salts.
THE LIVER unites water, fat, and albumen, with phosphoric and other acids, and lime, iron, soda, and potash.
THE LUNGS are formed of two substances: one like gelatine; another of the nature of caseine and albumen, fibrine, cholesterine, iron, water, soda, and various fatty and organic acids.
How these varied elements are held together, even science with all its deep searchings has never told. No man, by whatsoever combination of elements, has ever made a living plant, much less a living animal. No better comparison has ever been given than that of Youmans, who makes a table of the analogies between the human body and the steam-engine, which I give as it stands.
|ANALOGIES OF THE STEAM-ENGINE AND THE LIVING BODY.|
|The Steam Engine in Action takes:||The Animal Body in Life takes:|
|1. Fuel: coal and wood, both combustible.||1. Food: vegetables and flesh, both combustible.|
|2. Water for evaporation.||2. Water for circulation.|
|3. Air for combustion.||3. Air for respiration.|
|And Produces:||And Produces:|
|4. A steady boiling heat of 212° by quick combustion.||4. A steady animal heat, by slow combustion, of 98°.|
|5. Smoke loaded with carbonic acid and watery vapor.||5. Expired breath loaded with carbonic acid and watery vapor.|
|6. Incombustible ashes.||6. Incombustible animal refuse.|
|7. Motive force of simple alternate push and pull in the piston, which, acting through wheels, bands, and levers, does work of endless variety.||7. Motive force of simple alternate contraction and relaxation in the muscles, which, acting through joints, tendons, and levers, does work of endless variety.|
|8. A deficiency of fuel, water, or air, disturbs, then stops the motion.||8. A deficiency of food, drink, or air, first disturbs, then stops the motion and the life.|
Carrying out this analogy, you will at once see why a person working hard with either body or mind requires more food than the one who does but little. The food taken into the human body can never be a simple element. We do not feed on plain, undiluted oxygen or nitrogen; and, while the composition of the human body includes really sixteen elements in all, oxygen is the only one used in its natural state. I give first the elements as they exist in a body weighing about one hundred and fifty-four pounds, this being the average weight of a full-grown man; and add a table, compiled from different sources, of the composition of the body as made up from these elements. Dry as such details may seem, they are the only key to a full understanding of the body, and the laws of the body, so far as the food-supply is concerned; though you will quickly find that the day's food means the day's thought and work, well or ill, and that in your hands is put a power mightier than you know,—the power to build up body, and through body the soul, into a strong and beautiful manhood and womanhood.
|ELEMENTS OF THE HUMAN BODY.|
|1.||Oxygen, a gas, and supporter of combustion, weighs||103||2||335|
|2.||Carbon, a solid; found most nearly pure in charcoal. Carbon in the body combines with other elements to produce carbonic-acid gas, and by its burning sets heat free. Its weight is||18||11||150|
|3.||Hydrogen, a gas, is a part of all bone, blood, and muscle, and weighs||4||14||0|
|4.||Nitrogen, a gas, is also part of all muscle, blood, and bone; weighing||4||14||0|
|5.||Phosphorus, a solid, found in brain and bones, weighs||1||12||25|
|6.||Sulphur, a solid, found in all parts of the body, weighs||0||8||0|
|7.||Chlorine, a gas, found in all parts of the body, weighs||0||4||150|
|8.||Fluorine, supposed to be a gas, is found with calcium in teeth and bones, and weighs||0||3||300|
|9.||Silicon, a solid, found united with oxygen in the hair, skin, bile, bones, blood, and saliva, weighs||0||0||14|
|10.||Magnesium, a metal found in union with phosphoric acid in the bones||0||2||250|
|11.||Potassium, a metal, the basis of potash, is found as phosphate and chloride; weighs||0||3||340|
|12.||Sodium, a metal, basis of soda; weighs||0||3||217|
|13.||Calcium, a metal, basis of lime, found chiefly in bones and teeth; weighs||3||13||190|
|14.||Iron, a metal essential in the coloring of the blood, and found everywhere in the body; weighs||0||0||65|
|16.||Copper metals.} Faint traces of both these metals are found in brain and blood, but in too minute portions to be given by weight.|
The second table gives the combinations of these elements; and, though a knowledge of such combinations is not as absolutely essential as the first, we still can not well dispense with it. The same weight—one hundred and fifty-four pounds—is taken as the standard.
|COMPOSITION OF THE BODY.|
|1.||Water, which is found in every part of the body, and amounts to||109||0||0|
|2.||Fibrine, and like substances, found in the blood, and forming the chief solid materials of the flesh||15||10||0|
|3.||Phosphate of lime, chiefly in bones and teeth, but in all liquids and tissues||8||12||0|
|4.||Fat, a mixture of three chemical compounds, and distributed all through the body||4||8||0|
|5.||Osseine, the organic framework of bones; boiled, gives gelatine. Weight||4||7||350|
|6.||Keratine, a nitrogenous substance, forming the greater part of hair, nails, and skin. Weighs||4||2||0|
|7.||Cartilagine resembles the osseine of bone, and is a nitrogenous substance, the chief constituent of cartilage, weighing||1||8||0|
|8.||Hæmoglobine gives the red color to blood, and is a nitrogenous substance containing iron, and weighing||1||8||0|
|9.||Albumen is a soluble nitrogenous substance, found in the blood, chyle, lymph, and muscle, and weighs||1||1||0|
|10.||Carbonate of lime is found in the bones chiefly, and weighs||1||1||0|
|11.||Hephalin is found in nerves and brain, with cerebrine and other compounds||0||13||0|
|12.||Fluoride of calcium is found in teeth and bones, and weighs||0||7||175|
|13.||Phosphate of magnesia is also in teeth and bones, and weighs||0||7||0|
|14.||Chloride of sodium, or common salt, is found in all parts of the body, and weighs||0||7||0|
|15.||Cholesterine, glycogen, and inosite are compounds containing hydrogen, oxygen, and carbon, found in muscle, liver, and brain, and weighing||0||3||0|
|16.||Sulphate phosphate, and salts of sodium, found in all tissues and liquids||0||2||107|
|17.||Sulphate, phosphate, and chloride of potassium, are also in all tissues and liquids||0||1||300|
|18.||Silica, found in hair, skin, and bone||0||0||30|
With this basis, to give us some understanding of the complicated and delicate machinery with which we must work, the question arises, what food contains all these constituents, and what its amount and character must be. The answer to this question will help us to form an intelligent plan for providing a family with the right nutrition.
THE EASIEST WAY IN HOUSEKEEPING AND COOKING.
Adapted to Domestic Use or Study in Classes