Object of Food.—The object of food is primarily to furnish the means for growth, repair, heat and energy. The mere gratification of appetite, which to the detriment of health too often is regarded with undue prominence, is a secondary consideration and merely incidental to nature's demand for nutrition.

Food, Half of Life's Battle.—It has been said that "food properly chosen, properly cooked and properly eaten is half the battle of life," and the practical value of the subject will readily be understood when it is considered that it plays an important part, not only in maintaining health, but in modifying and curing diseases.

The Problem of Diet.—If all members of the human family were alike it is obvious that a bill of fare could soon be arranged which would give every person the most perfect nourishment; but as we each differ, in some smaller or greater degree, from all others of our fellow men, it is necessary to study the problem of diet, as modified and limited by our own individual peculiarities and surroundings. Age, sex, occupation, climate, nationality, and so forth, all influence the quantity and the character of food required, and, on the other hand, the amount and nature of food taken govern to no little extent the temperament and characteristics of people. Prior expresses this truth poetically when he says;

"Was ever Tartar fierce and cruel
Upon the strength of water gruel?
But who can stand his rage and force
If first he rides, then eats his horse?
Salads and eggs and lighter fare
Tune the Italian sparks guitar;
And, if I take Don Congreve right,
Pudding and beef make Britons fight."

How Food Affects Races.—It has been pointed out, and doubtless with some truth, that racial distinctions are in a measure the result of the character of the food taken, and that the Irish and the Hindo would not have submitted so supinely to the rule of England had their diet, which consists chiefly of vegetables, been more highly nutritious like that of the British.


How Food is Appropriated.—In considering the subject of food, it is important to understand the method by which it is appropriated by the system and converted into blood, flesh, bone and other tissues, and how it is utilized in the generation of heat and force.

Change of Fluids and Tissues.—During our whole lives the fluids and the solid tissues of our systems are constantly undergoing change. New materials in the form of infinitely minute particles of muscle, nerve, and so forth, are being produced, while the old and worn-out atoms of these structures are removed with ceaseless activity. "While this incessant movement of these constituents of our bodies is not perceptible to the eye, even when aided by the most powerful microscopes, it nevertheless goes on, and must go on as long as life continues. In fact, the researches of physiologists tend to show, with a large amount of certainty, that the health, strength and vigor of the whole and of every part of the body is in proportion to its youth and newness. Thus it is that exercise, under due regulation and management, is a hygienic means of such great value in strengthening and developing the whole frame, especially the muscular system.

Relation of Natural Forces.—In endeavoring to reach the "bottom facts" of our knowledge in regard to the forces we derive from the food taken into our stomachs, we must bear in mind that, in our own bodies, as in the whole universe around us, we have, from a scientific point of view, to deal only with material entities of various kinds and properties which we call matter, such as the chemical elements oxygen, carbon or sulphur, and their compounds; and principles of action, which we denominate forces, among which may be instanced heat, electricity, and the attraction of gravitation, as types.

Natural Forces.—The doctrine of the correlation of forces, abstruse as it sounds at first, is simply, as regards two of them, namely heat and mechanical motion, an extension of the commonly observed fact that motion, by causing friction, produces heat, as we see in using an ordinary Lucifer or friction match. Every time we strike a match we demonstrate that motion may produce heat; and to expand this idea into the doctrine of correlation (or relationship) of forces, it is only necessary to prove by careful and ingenious experiments, as was first done by Mr. Grove and Mr. Joule, that any certain amount of motion applied in any conceivable way to the production of heat, causes always exactly the same amount of heat, and contrariwise, a particular quantity of heat applied to the production of motion, originates always the same quantity of movement, no matter by what kind of machinery it is applied.

Heat and Motion.—In this way we can, by mechanical experiment, establish the existence of a correlation—or, to use the more familiar word introduced above, a relationship—between heat and mechanical motion, and this relationship has been found to be that the force of a weight of 772 pounds falling one foot would, if converted into heat, raise the temperature of one pound of water one degree of Fahrenheit's thermometer.

Muscular Effort.—After clearly comprehending this idea, it is only necessary to grasp the further suggestion that, if a man is hired to lift up again the weight of 772 pounds, which in falling one foot gave us our unit of heat (namely, the heating of one pound of water, one degree), we farther establish, by the additional experiment, a relationship or "correlation" between the number of muscular efforts he is required to make and that same heat unit.

Food Required.—Lastly, if we weigh the extra beefsteak or half-peck of potatoes he needs to eat, to enable him to perform so much extra labor, we find out the equivalent in ounces of food for the requisite amount of muscular exertion employed, which is again the equivalent of the mechanical motion produced, and this in turn is the equivalent of our (arbitrarily assumed) unit of heat, the quantity of heat which will raise one pound of water one degree.

The Four Natural Forces.—Thus, even those readers who make no pretensions to scientific culture can, it is hoped, understand the nature of that mutual relationship or correlation which exists between these four natural forces, to wit, heat, mechanical motion (of falling or lifted weights), muscular exertion and food.

What Food Is.—Food, then, is any substance which, when taken into the animal body, may enter into such new chemical combinations that it gives out its dormant force in the form of heat, muscular movement, nerve power, and so forth.

How Food Nourishes.—If an article of food is completely combined with oxygen in the human system, it yields up all the force which it is capable of affording; but if it is not so adapted to the wants of the body as to be fully oxidized or burnt up, part of its force passes off with other refuse matters, and is wasted, as far as that man's nutrition is concerned. It is by learning how to avoid this waste, as well as to escape the injury, excess of undigested food is apt to cause to the digestive organs, that a careful study of the articles of diet suitable for each individual, in accordance with the facts and conclusions detailed below, may be made so profitable and beneficial to every one.


Cell Organization.—All animals and vegetables are built up of minute, separate, organized bodies, called cells, which are put together like stones in a pavement, so as to form the skin, the muscles, the nerves, and so forth. The cell-elements or cells are made up of a nucleus or central living mass, which may be aptly compared to the yolk of an egg.

Protoplasm.—Around this nucleus is gathered a little lump of formed material or protoplasm, corresponding to the white of an egg, and the whole is enclosed in a delicate membrane resembling that which lines the egg-shell. These cells are extremely small, varying from one four-thousandth of an inch to one five-hundredth of an inch in diameter. In the epithelial scales or cells, which are packed together to form the skin, as already mentioned, the average diameter is about one fifteen-hundredth of an inch.

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Plant Cells.—The marginal illustration shows the cells from the root of a plant magnified five hundred and fifty times. At 1 appear two young cells with thin walls marked W, the nucleus N, and a central spot called the nucleus N'. The protoplasm of each cell is seen occupying the space around the nucleus, and within the cell-wall. At 2 are exhibited a couple of older cells, with thicker walls, having vacant spaces or vacuoles, S, filled with fluid sap. At 3 are displayed still older cells, with a further decrease of the protoplasm, which has apparently been used up in building the yet thicker cell-walls. But although cells are thus seen to enlarge, the chief part of the growth of plant or animal is brought about by the multiplication of cells, which divide and subdivide sometimes with great rapidity.

Cells of Wood, Bark and Pith.—Besides increase of size of an animal by this multiplication of cells, we have differences of structure, resulting from variations in the form and composition of the fully-developed cells, such as those of the wood, bark and pith of a plant, or the muscle, nerve and skin of an animal. Lastly, by the death of larger or smaller groups of cells, are produced the decay of vegetable and the ulceration of animal organisms.

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Building of Human Organs.—The different organs of human bodies and those of the inferior animals are built up of cells very similar to those found in the vegetable kingdom, as is illustrated by the adjoining figure. This cut shows the liver-cells of man, with the nucleus, a, and oil-drops, b, in their protoplasm. At c is depicted a free nucleus, that is, one from which the cell-wall and the protoplasm have been accidentally torn away; and at d is shown a large cell with two nuclei, illustrating the tendency to occasional twin-formation, which seems to run throughout all animated nature.

First Step Toward Human Development.—The first step toward the development of a new being in that wonderful yet hourly miracle of reproduction, as, for instance, of a young chicken inside an egg, is the division of the yolk into a great number of little rounded parts, which soon present the appearance of a heap or mass of cells, which for a time cannot be distinguished from the white cells in the blood of the parent hen. Gradually, however, as the operation of hatching progresses, certain groups of these cells vary under the influence of the vital force from other groups, until, by a continuing process of development, the liver, the heart, the skin, and so forth, are completely formed.

Cell nourishment.—In chickens, and birds generally, the young creature is nourished until large enough to pick up its own food by the contents of the egg, but in animals which bring forth their young alive, a curious natural provision is made for supplying the requisite nourishment from the blood of the mother. After birth, however, the necessity for food immediately becomes apparent, and in order that mere existence shall continue, external nourishment of some sort must be regularly supplied. Furthermore, if growth and complete development are to go on, this nourishment must be accurately proportioned in kind, quantity and composition to the exact needs of the infant animal or man.


Analysis of cow's milk shows it to contain—

Albumen and casein....................................  54.05
Butter ...............................................  43.05
Milk Sugar............................................  40.37
Salts ................................................   5.48
Water ................................................ 857.05
Total ...............................................1,000.00

While this forms a suitable diet for young children, who, though rapidly growing, expend in labor comparatively little muscular force, it fails, to meet the requirements of active adult life.

Kinds of Diet.—Nor, notwithstanding much argument to the contrary, does an exclusively vegetable diet seem best adapted to man's needs. The evidences derivable from the form and arrangement of the teeth, the structure and functions of the alimentary canal, and the results of direct experiment, all indicate that, in the present age of the world at any rate, mankind thrives best, as a general rule, upon a mixed animal and vegetable diet.

Amount of Food Required.—The requirements of a full-grown individual may be estimated by accurately determining, as has been done by scientific men, the quantities of the chemical elements carbon, hydrogen, nitrogen and oxygen, which are cast off from the body by the bowels, the kidneys, the skin and the lungs, every twenty-four hours, and then calculating what quantities of various articles of food, containing these chemical elements, must be eaten daily to supply this waste.

What Foods Must Supply..—For instance, if we find, as some English investigators have done, that a gang of one hundred average prisoners cast off every twenty-four hours, from their lungs, kidneys and bowels, about seventy-one and a half pounds of the element carbon, and four and a quarter pounds of nitrogen, it is obvious that carbon and nitrogen must be supplied to this amount in the food the gang of prisoners eat in order to make up far what is excreted. If they were to be fed upon bread and water alone it would require 380 pounds of the staff of life daily to keep them in good health, because it requires that weight to yield the four and a quarter pounds of nitrogen which they daily cast off In the ways just mentioned. But in 380 pounds of bread there are 128 pounds of carbon, which is about fifty-seven pounds more than would be needed to replace what these men would excrete.

Meat Food.—On the other hand, should the authorities try the experiment of giving them animal food only, it would be necessary to allow them. 350 pounds of lean meat, because no less than that amount would contain, the seventy-one and a half pounds of carbon necessary to replace the quantity of this element excreted; but lean meat contains proportionately a very large amount of nitrogen, and in 354 pounds of it there would be found 109 pounds, or 105 pounds nearly in excess of what the prisoners really required, and which would therefore be wasted as food.

Mixed Food.—In the former case which we have supposed, each man would have to eat about four pounds of bread, and in the latter about three and a half pounds of meat every day, in order to avoid losing strength. In the first instance, there would be a good deal of starch in the bread, and in the second case, a considerable bulk of nitrogenous material, which would be quite unnecessary as food, and apt if taken into the stomach to overload it and derange its functions.

A True Mixed Diet.—The true way is to resort to a mixed diet, and if such were to be adopted in this instance, we would probably find that 200 pounds of bread, with sixty pounds of meat, would answer every purpose. Two hundred pounds of bread contain, besides water, sixty pounds of carbon and two of nitrogen, and sixty pounds of meat about twelve of carbon and two and a quarter of nitrogen; making, it will be observed, exactly the quantity of each of the primary elements cast off by the 100 men daily as waste matter from the processes of life.

Property of Milk Food.—It is manifest, according to this calculation, that milk is not accurately suited to supporting an adult population, because it contains too little carbon and too much nitrogen to supply the waste. This excess of nitrogen is well suited to the young animal which is actively engaged in adding to its muscular development, but is not adapted to the full-grown man, who is obliged to produce force, or its equivalent, heat, by the slow combustion of carbon in his body. It is to supply this excess of carbon, beyond what exists in milk, that all the world over bread or starch which is rich in carbon, in some form, is gradually added in larger and larger proportions to the food of a growing child.

Proper Diet Lists.—Such calculations, in regard to the other constituents of our food, form a basis of the utmost value for the economical arrangement of diet lists, and the distribution of limited means, as, for example, in armies and navies, with the least possible waste of the ingredients at command.


Number and Arrangement.—In the adult human being the teeth, when perfect, are thirty-two in number, and are arranged in the following order: First, in the middle of each jaw, are the four incisors or cutting teeth; next, come one on each side of the group of incisors, the two canine or dog-teeth, so-called because they are very large and conspicuous in a dog's mouth; the next pair of teeth, situated just back of each canine tooth, are named the first and second bicuspids, on account of their having two points or cusps; behind these, again, we find the first, second and third molars or grinding-teeth.

The Molar Teeth.—The last, or third molars, four in number, counting two in each jaw, of course, have received the name of the wisdom-teeth, because they appear about the time that people grow up and are supposed to have arrived at years of discretion.

Children's Teeth.—The permanent teeth are preceded during childhood by a smaller set, only twenty in number, which are styled the deciduous teeth, for the reason that they fall out or are pushed out by the larger and stronger permanent set. These deciduous teeth begin to come through the gums of babies when they are from six to twelve months old, and unfortunately give rise to much of the pain endured in childhood. The adjoining figure shows how the second set of teeth comes in behind the first, or deciduous teeth, pushing these latter out of the jaws from the sixth to the tenth or twelfth year of life.

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Structure of Teeth.— Each tooth has, as can be readily seen by cracking open one from a dead animal, a very hard outside shell, composed of what is called the enamel, a softer and thicker body-substance, denominated dentine or ivory, and a hollow place near the centre of this dentine, named the pulp-cavity, which during life is filled with a mass of nerves and blood-vessels. The pulps or nerve of a tooth is exceedingly sensitive, and acutely painful on the slightest touch, or even from mere exposure to the air, as, for example, by the breaking off or decaying away of some portion of the dentine or tooth-bone which naturally protects it, and which when removed gives rise to toothache.

Care of Teeth.—The prevention of such suffering lies in avoiding the decay as long as possible by keeping the teeth clean, refusing corrosive articles of food or medicine, and, when cavities begin to form, having them stopped up or filled by a skillful dentist before they have time to reach the nerve.

Effect of Hard Brushes.—While frequent cleansing of the teeth is important, it is not advisable to brush them too much with hard toothbrushes, and especially with gritty tooth-powders, thus irritating the gums and wearing away the very enamel which it is our object to preserve.

What to Avoid.—The teeth should never be used to break hard objects; hot and cold liquids, especially in quick succession, ought not to be brought in contact with them, as in drinking; and strong vinegar, syrups and sweetmeats ought likewise to be kept away from the teeth. If candies are eaten at all, or at rare intervals, the sugar remaining between the teeth and around the gums should be promptly washed away by rinsing the mouth.


Tongue Function.—Besides being the organ of taste and the chief agent in the production of speech, the tongue performs an important duty in bringing different portions of a mouthful of food under the molar teeth during the operation of mastication or chewing. This office of the tongue is shown to be one of great usefulness, by the fact that when paralyzed, either wholly or in part, great difficulty is experienced in chewing food, because it cannot be pushed between the grinding surfaces of the back teeth.


Breaking up the food into a sort of coarse powder is only the first step in its proper preparation for digestion. It must next be mixed with the liquid of the mouth, called the saliva, which has the remarkable power of turning the insoluble starch of bread and other starchy foods into soluble sugar.

Number and Location.—The salivary glands, whose business it is to manufacture the saliva, are six in number, four being situated under the tongue and the jaw, and the others seated deeply in the cheeks in front of the ears. These are called the parotid glands, and are remarkable for being the parts affected by the contagious disease named mumps.

Secretion of Saliva.—The saliva is poured out by different ducts, into various parts of the mouth, so as to become intimately mixed with the food. Its active principle, named ptyalin, plays a very important part in the digestion of the amylaceous substances, that is to say, articles of diet, such as bread, potatoes, corn, and the like, which are chiefly composed of starch.

Thorough Mastication.—It is, therefore, highly necessary that chewing should be performed slowly enough to give time for a sufficient quantity of saliva to be secreted, and to be completely mixed with the food, as want of care in eating too fast is apt to be followed by the disease called dyspepsia, as already mentioned. It is difficult to urge too strongly the importance of a thorough mastication of vegetable food.

Quantity of Saliva.—In the human being, the saliva is produced in the quantity of nearly four pints daily during health; but the secretion of this very important agent in the digestive process is powerfully affected, by mental emotions, such as fear, anger or pity, and it is also largely influenced by certain medicines, such as belladonna or deadly nightshade, even in comparatively small doses.


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Operation of the Muscles.—The entire process of swallowing is a series of associated muscular acts, quite independent of the force of gravitation, as may be seen in animals drinking with their heads downward. Although these complex movements follow each other without any check or pause, it is common to divide them into three stages, the first of which is the voluntary one of pushing the mass of chewed food back to the upper part of the throat or pharynx, so that it is grasped by the involuntary muscles, which send it on downward to the stomach. This operation the muscles which form the tube called the throat or gullet accomplish by relaxing in front of the morsel of food which is being swallowed and contracting behind it. The adjoining figure exhibits the deep muscles of the cheek and the pharynx with adjoining parts. The circular muscle of the mouth (1) and the buccinator or trumpeter's muscle (2) help the tongue to push the food back to the upper margin of the gullet, where it is seized upon by the three constrictor muscles (3, 4 and 5) of the pharynx, and pushed down the gullet or esophagus, which is represented as being cut off at 6.

The Glottis.—In front of the pharynx is an opening into the windpipe named the glottis, through which we breathe, but which must, of course, be closed during the operation of swallowing, in order to prevent our food from dropping into it.

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The Gullet.—The gullet or esophagus is a muscular and membranous tube, about nine inches long, which if dissected out would look very much like a thin piece of rubber hose, such as is used for watering gardens. Its duty is to carry the food from the pharynx to the stomach, and in order that it may not get stopped up by food getting wedged in it, this pipe, in consequence of its muscular structure, has the power of contracting itself in successive portions from above downward, so as to push onward the articles of diet which are being swallowed.


Shape.—The human stomach is a somewhat egg-shaped bag, the walls, as the substance of the bag is called by anatomists, of which are made up first, counting from the inside outward, of a layer or coat of mucous membrane which is similar to, and continuous with, the moist red mucous membrane which we see lining the mouth and throat. Outside of this is a coat of muscular fibres, some running around and others diagonally across the sack, and then outside of these again is a layer of membrane or skin.

Stomach Communication.—The stomach communicates, at its upper part on the left side of the body just below the heart, with the gullet which opens directly into it, and it empties itself, on the right side, into the upper portion of the small intestine, through a sort of valve, which has received the name of the pyloric orifice, because the word pylorus means a janitor or gate-keeper.

The arrangement of the stomach and other portions of the digestive apparatus, or alimentary canal, or alimentary tract, is well shown in the foregoing figure.

Gastric Juice.—The whole of the mucous membrane, or inner lining of the stomach, is filled with glands, somewhat similar to the salivary glands, but so small that they can scarcely be seen with the naked eye. These glands all open into the cavity of the stomach, and their business is to manufacture, from the blood which flows around them, in a network of fine blood-vessels with very thin walls, that important fluid, the gastric juice, remarkable for having such a wonderful solvent power upon the meat, eggs and other foods which constitute what is called the nitrogenous portion of our diet.

Quantity of Gastric Juice.—The quantity of gastric juice very much exceeds that of the other digestive fluids, being about a gallon and a half every twenty-four hours.


This is the largest organ in the body, being situated below the right lung. Its office is the secretion of another digestive fluid known as bile.

Bile.—About one quart of bile is daily produced, it being intimately connected with the digestion of fats. Interference with its proper secretion is largely concerned with the production of constipation and the train of symptoms ordinarily known as biliousness.


The pancreas is a long, thin gland, situated behind the stomach, and constituting, in the ox, part of what is sold under the name of sweetbread.

Pancreatic Fluid.—This is secreted daily to the extent of about a pint and a half. It supplements the action of the saliva and the bile by helping to dissolve the starchy materials and to finely subdivide the fatty substances.


The small intestine is a membranous pipe or tube about twenty feet long, but twisted and looped together in such a way as to occupy only the small space of a few inches in the cavity of the abdomen, which forms the lower half of a person's trunk, or body as it is often called, in contra-distinction to the limbs and head. This tube is continuous with the pyloric opening of the stomach at its upper end, and at its lower extremity empties into the side of a much wider membranous tube, about five feet in length, called the large intestine.

The Large Intestine.—Most of the large intestine has received the name of the colon, and it may be justly compared to the main sewer of a city, into which pass all the waste refuse and foul materials which are of no further use, and must be gotten rid of as soon as possible.


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Mucous Membrane.—The whole intestinal tube is lined with a mucous membrane, and in the small intestine this has its inner surface covered with hundreds of thousands of little tongue-like projections called villi. These villi are represented as they appear when highly magnified in the marginal illustration, which is a diagram of a thin slice cut lengthwise from the wall of the tube.

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Folds of Membrane.—Although the intestinal canal is so prolonged as to measure, when stretched out, over twenty-five feet, its internal surface is not sufficient to perform all the work of absorbing the digested materials of diet. Hence, the lining mucous membrane is thrown into folds, as shown in the appended woodcut, simply in order, it appears, to afford surface enough for absorbing all the nutriment from articles of food, and so disposing of the substances we swallow to the best and most economical advantage.


In order that the food-stuffs, when altered by the digestive process, may be of any real use to the animal economy, the nutritive materials must be distributed through the different tissues and organs of the body.

Digestion Not Sufficient.—The mere digestion of food is by no means sufficient, and no matter how much we eat, it would accomplish nothing toward keeping our muscles, hearts and brains in active operation, unless food-elements were absorbed after digestion into the blood, and assimilated from it into the very structure of all the different portions and organs of the animal frame.

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The Lymphatics.—As shown in the adjoining illustration, the lacteals, LAC., which take their origin in the villi of the small intestine, converge and unite together, meeting the combined lymphatics of the lower extremities in a kind of bag, called the receptacle of the chyle, which is situated deeply in the abdomen and in front of the spine, near its middle. From this the mingled chyle and lymph are carried along the thoracic duct, up to the root of the neck on its left side, where they are poured into the large veins, and so mix with the blood and become a part of that vital fluid.

Distribution of Nutriment.—The nutritious principles of the food having been absorbed by the lacteals and carried onward by the lymphatics to the general circulation are now distributed to the various organs by the blood.


Through these channels the blood is kept in constant motion by the action of a muscular pump, the heart, first passing into strong-walled branching arteries, the walls of which gradually become thinner as the branches grow smaller. These end in a network of delicate capillaries, or hair-like tubes, through which the crimson tide flows slowly into the wider, soft-walled veins, appointed to carry it back to the heart, and thus complete the round of the circulation.

Blood Function.—In its course, it receives the nutritive materials from the stomach and intestines after digestion, the special products of the liver, spleen and the lymphatic glands, and the oxygen absorbed from the air in the lungs. It therefore contains and carries to their destination all the materials required for the chemical and vital changes of the various tissues necessary to life.

Waste Material.—While passing through the capillary networks of the different organs and structures, it takes up the waste materials resulting from the wearing out and decay of these portions, and carries them to the proper point of escape from the body, as, for example, the kidneys or the bowels; at the same time the nutriment needed to rebuild the worn-out organs, is allowed to ooze through the delicate vessel-walls of the capillaries, and be diffused into the surrounding tissues.

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Capillaries.—In the human being it is difficult to demonstrate the circulation of the blood in the capillaries, but the fineness of their network and the pressure of the blood which is kept up in them to force along the vital fluid may be readily shown by pricking the finger with a needle, the point of which, no matter how small it is, can scarcely fail to penetrate some minute blood-vessel, and let out a tiny drop of crimson blood. This wonderful arrangement can be most conveniently demonstrated in the thin membrane of a frog's foot, stretched out under a microscope magnifying two hundred times.

Arteries and Veins.—Of the two sets of blood-vessels, the arteries, which convey the blood from the heart to the tips of the fingers and the ends of the toes, carry bright scarlet blood, and are generally deeply seated in the interior of the body and limbs, so as to be, as far as possible, out of harm's way. The veins, which lie more generally near the surface of the body, as, for example, just beneath the skin on the back of the hand and arm, are filled with dark purple blood, which is much less pure than the arterial fluid, because it contains large amounts of the broken-down materials, the ruins, as it were, of the various bodily organs, which are now on their road to be thrown away out of the system through the lungs, the kidneys and the bowels.

The Heart.—The heart has small chambers at the upper part to receive the blood, and larger, thicker chambers at the lower end, called ventricles, to pump it out. The human heart is also double, having a right side made up of a moderately strong auricle and ventricle, to send the blood to the lungs, and a powerful left side or left heart, with a thicker auricle and a very thick, strong ventricle, to drive blood to all other parts of the body.

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The Illustration.—This arrangement of the two independent sides of the heart will be better understood by the aid of the diagram in the margin, which represents the two sides of the heart as separated, as they are in reality in the human breast, although there fastened together and apparently forming but a single organ. The arrows indicate the direction of the blood-current in the entire round of it's circulation.

Shape of the Heart.—The human heart is a pear-shaped muscle, about the size of the fist, hollow, like a bag, but with very thick walls. It is divided inside by fleshy and membranous partitions into four parts, very much as a four-roomed house is divided into rooms by its ceiling and partitions, with communicating doors through each of the latter.

The Valves.—The valves consist of a skin or membrane hung across each side of the opening between the chambers of the heart, like curtains, in such a manner that the blood, in running one way, presses them flat against the sides of the hole, and then, as the heart's contraction attempts to drive the vital fluid back again, some of the blood is forced in behind the curtains, and swelling them out so that they meet in the middle, makes them entirely shut off the return-current of the blood.

Pulsations.—The throbbing of the heart may be felt on the left side of the body, near the lower edge of the ribs, and the beating of the pulse, which in health corresponds to the pulsations of the heart, at the wrist and over the course of large arteries elsewhere, when situated sufficiently near the surface.

Number of Beats.—In adult men these beats usually number about seventy, in women about seventy-five, and in children still more frequent; in infancy being about one hundred and twenty in a minute, and decreasing in frequency with increasing years. Within the limits of health the heart's action may vary considerably, some habitually having a rapid and others a sluggish pulse, while in the same individual such conditions as exercise, emotion, depression or even the process of digestion, may decidedly modify its frequency.

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Course of Circulation.—The left side of the heart, marked L.H. in the figure, pumps the blood into the systemic arteries, and thus keeps these vessels over-filled; the larger systemic arteries, A., by their elasticity, exert continuous pressure on the blood with which they are distended; the smallest systemic arteries, A', by their vital contractility, check and regulate the amount of blood flowing out of the larger arteries into the capillary network, and thus keep up the constant pressure or tension in the larger arteries; the systemic capillaries, marked S. C., are the portions of the vascular system where the great operations of the blood are carried on, that where the worn-out particles from all the tissues of the body are removed and the new atoms for rebuilding these same tissues are supplied; the wide systemic veins, V., are the passive channels conveying the impure blood back to the right side of the heart; the right or pulmonary side of the heart, B.H., pumps the blood into the arteries of the lungs and distends them, though less fully than is the case with the systemic arteries; by the pulmonary arteries, P.A., the blood is carried through the pulmonary arterioles or smallest arteries, Pa, to the pulmonary capillaries, P.C., where it is exposed to the inbreathed air and exchanges its poisonous carbonic acid for the active lifegiving oxygen; the letters Lh indicate the lymphatics, ending in the thoracic duct, as already described, and receiving in their course the lacteals, Lc, which absorb the nutriment of the food from the stomach and intestines, designated by I. in the diagram.

Description of Blood.—Human blood, when exposed to the air, from which it rapidly absorbs oxygen, is of a bright scarlet color; but when deprived of oxygen it is dark purplish red. This difference is the great characteristic distinguishing arterial from venous blood, and should always be borne in mind when attempting to staunch the bleeding from a wound, since entirely different treatment is needed in the two cases.

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Red Corpuscles.—The blood is not a red fluid, as it appears to be when first shed; it is composed of a watery portion, called the plasma, which has a light yellow color, and an immense number of minute corpuscles, which give to the blood its crimson hue. These little bodies, which are called the red blood corpuscles, are exhibited in different positions in the accompanying cut, as they appear when highly magnified; the illustration also shows two white or colorless corpuscles, one on the extreme left in a rounded condition, and the other at W, misshapen and entangled in some fibrin threads.


The foods may be divided into the following classes:

1. Nitrogenous substances, or proteids, which go to form the tissues of the body, and are represented by meat, eggs, the casein of milk, and, other substances consisting chiefly of albumen.

2. The fatty or heat-producing aliments, which are derived from both the animal and vegetable kingdoms, although chiefly from the former; they include the animal fats, such as lard or suet, butter and the vegetable oils, among which that from the olive is the one most consumed by civilized man.

3. The carbo-hydrates, or substances containing carbon and hydrogen without nitrogen; these are the saccharine or sugary, and the amylaceous or starchy ingredients of human diet, comprising therefore sugar, molasses bread, potatoes, beans, etc.

4. The saline or salty articles, consisting largely of common kitchen salt, with potash, lime, magnesia, and a little iron in various combinations. These ingredients of the human body, small as some of them are in amount, possess a very great importance.

Animal Food.—When men are called upon to perform any extra amount of severe labor, involving great muscular exertion, there is no doubt that an additional supply of meat is of great service.

Fatty Foods.—In regard to the functions of the fatty constituents of food, we may at once conclude that, since the diet resorted to by inhabitants of cold countries invariably contains a large proportion of fatty ingredients, these elements play an important part in the maintenance of animal heat. Indeed, it has been demonstrated by experiment that the respiratory or heat-producing powers of fat are two and a half times greater than are those of the vegetable hydro-carbons, such as starch or sugar.

Saccharine and Starchy Foods.—The saccharine and starchy constituents aid the fatty matters in developing animal heat, although they are much less efficacious in this respect. Starch is, however, capable of being rapidly converted into fat by the wonderful operations of nature's laboratory, as we see in the process of fattening pigs upon corn for market, and in this way a large store of the best heat-producing material may be laid up in the system as a provision for the winter's cold.


Soups and Broths.—Where economy of nutriment is an important object to be attained, it is probable that the production of broths and soups, from vegetables and meat in combination, affords many and great advantages. In making nutritious broths with a fair allowance of butcher's meat, it is advisable, when possible, to cook the vegetables separately, and the meat, if intended to be eaten with the soup, should be cut up into small pieces. In any case, the meat should be put into cold water, but should not be boiled, except when the vegetables are cooked in the same utensil, a temperature of about 150 degrees Fahrenheit being quite sufficient. If the meat is plunged into hot or boiling water at the outset, the external layer of albumen is coagulated, and the juices are prevented from exuding,

Boiled Meat.—In boiling meat, on the other hand, when the object is to retain as much as possible of the soluble juices in the meat, the piece ought to be of good size, and it should at once be plunged into boiling water, to coagulate the outside albumen. After being kept boiling for about five minutes, the saucepan should be placed aside, and the temperaature allowed to lower gradually; or it may be lowered by the addition of three pints of cold water to each gallon of boiling water.

Boiled Fish.—In boiling fish, the addition of salt makes the flesh firmer and more retentive of the flavor. In cooking green vegetables, they should first be carefully washed in cold water, but not allowed to remain in it, then plunged into boiling water and cooked rapidly. Potatoes should be boiled in their skins, and after boiling for about five minutes most of the water should be poured off, and then the potatoes should be steamed.

Roasted Meat.—In roasting meat, the joint should be placed at first before a brisk, hot fire, with a view, as in boiling, to coagulate the outside albumen, and then the roasting may be conducted more slowly.

Stewed Meat.—Stewing has this advantage over dry-baking—that there is no risk of charring, and the meat is rendered juicy and tender. Tough and strong-flavored meats are, perhaps, best cooked in this way, because they can be rendered very palatable and digestible by the addition of vegetables and seasoning.

Fried Meat.—Frying is even worse than baking, unless very carefully done; but broiling on the gridiron is an excellent way of cooking chops, steaks, kidneys and small dishes of fish or fowl.


Not until 1825 was the question of the relative power of the stomach to digest different foods satisfactorily demonstrated.

Liquids.—Liquid, such as water, both pure and when containing a small amount of nutriment in solution, as is the case with beef-tea or broth, are often quickly absorbed by the lining membrane of the stomach, very much as water is sucked up by a sponge, and pass directly into the blood.

Milk.—Milk is usually coagulated or clotted as we see it when curdled by rennet, which is the dried stomach of the calf, by one of the ferments in the gastric juice, but it is commonly soon dissolved again and absorbed.

Bread.—Wheat-bread composed, as already mentioned, chiefly of starch, cannot be regarded as holding a place among the quickly digestible foods, since it has been found to require nearly three hours and a half for solution.

Eggs.—Eggs, if eaten raw, may be digested in two hours, but if boiled soft may take three hours, and if hard boiled or fried, require three and a half hours for digestion.

Meats.—Meats of various kinds differ a good deal in their digestibility; thus, for example, boiled turkey has been found to disappear from the stomach in about two hours and a quarter; boiled lamb in two and a half hours, and roast beef in three hours; while fried pork requires over four hours, and roast pork five hours and a quarter for complete digestion.

Fish.—Fish prove, as a rule, more easy to digest than meats; and the ordinary vegetables present less difficulty to the action of the stomach than bread, boiled rice being particularly manageable and requiring only about an hour for its entire solution.

Rules Regarding Meals.—In regard to the periods for eating, experience proves that habit is one of the most important agents in determining the times we ought to partake of nourishment. When a systematic regularity in respect to the period when we introduce food into the stomach is observed, the digestive processes are all better accomplished, and the food is more thoroughly and completely assimilated, than when meals are eaten irregularly.

Time for Meals.—The prevailing custom in this country is to breakfast, soon after rising in the morning, on food nourishing enough to repair the exhaustion consequent upon the long fast of the night, and yet not so heavy as to overload the stomach during the morning, when the most active exertion of the day is usually performed. Whether the most substantial meal be taken at mid-day or in the evening must depend largely upon individual preference, convenience, occupation, and so forth.

Exercise.—A very deliberate walk for half an hour or so in the open air, when the weather is not too cold, accompanied by the stimulus of cheerful, but not exciting nor absorbing, conversation, is a material aid to digestion.

Thorough Mastication.—As already indicated, the thorough mastication of articles of diet, especially by the third set of teeth, is essential to proper digestion, because, during this process of chewing, nature intends not only that the alimentary substances shall be broken up into a coarse powder, but also that this powder shall be completely mixed with the saliva, which has a powerful influence in preparing the starchy ingredients for solution. Hence persons should eat very slowly, chew thoroughly and move the mouthful of food freely about from one cheek to another, in order to amply impregnate it with the fluids of the mouth, and this precaution is particularly valuable when the food happens to be less digestible in quantity or quality than is customary.

The diagram on following page shows the percentage of the different nutritious elements of food in eight of the common articles of diet.

Effects of Overeating.—An English observer has calculated that for every death from starvation, seven occur from the effects of overindulgence in food. When the stomach is overloaded with food beyond its power of digestion, nature often relieves the abused organ by the process of vomiting, which no doubt frequently saves people who violate the laws of hygiene in this respect from the penalty of death, or at least of prolonged illness. When, however, the digestive organs are not unloaded in this manner, the ordinary chemical changes, which occur in warm, moist animal and vegetable matter outside of the body, set in, and fermentation or putrefaction occur, large quantities of gas being some times produced.

Excess of Nitrogenous Food.—When a superabundance of proteid substances is eaten, and perhaps imperfectly digested, whilst at the same time, as often happens, a diminished quantity of exercise or labor is performed, there must almost necessarily be a disproportion between the oxygen inhaled by the lungs and the nitrogen absorbed from the food, when they meet in the blood, and therefore a disturbance of the assimilative processes. It is probable that gouty and perhaps rheumatic affections arise partly in this way, although the direct influence of certain alcoholic drinks in producing gout is indisputable.

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Excess of Starchy Food.—Superabundance of starchy articles of diet appears to be less directly hurtful to the system, because a larger proportion of the excess passes off from the bowels in an unchanged condition. Troublesome corpulence may sometimes result, however, from eating too much starchy food, and it has been supposed that attacks of diabetes, a disease which is characterized by the presence of sugar in the urine, are occasionally due to the same error in diet.

Effects of Insufficient Food.—Insufficient nourishment is followed by loss of flesh, weakness, faintness, and, if prolonged sufficiently, by extreme emaciation, hallucinations and delirium. The blood decreases in volume, the temperature is lowered, the respirations become fewer, palpitation, vertigo, diarrhoea and dysentery ensue, the eye is glassy and ulceration of the cornea occurs.

Contaminated Food.—Food is often rendered unwholesome and unfit for use by inherent disease by contamination with poisonous substances and by putrefactive changes. Moreover the peculiar power of absorption possessed by some foods, as milk, pineapples and bananas, is capable of causing the transmission of certain diseases.

Decomposing Food.—Decomposing food may give rise to alarming and fatal poisoning through the absorption of septic materials into the system. It is probable that where chemical analysis fails to reveal a cause for death, many cases giving evidence of violent gastro-intestinal inflammation or of profound impression of the nerve centres, are in reality due to such causes.

Meat of Diseased Animals.—The meat of animals affected with such diseases as pleuro-pneumonia, murrain, anthrax, tuberculosis, Texas cattle fever and parasitic affections, as tape worm and trichinosis are unfit for food, and precautions observed to guard against their employment.

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Adulteration of Milk.—The results of the adulteration of milk are mainly those caused by withholding certain nutritious principles from the food supply. Their evil effects are seen particularly in infants fed upon cow's milk, who are thus deprived of much that is necessary to their subsistence and growth. The skimming of milk, or the addition of water, are alike productive of this result.

Transmission of Disease by Milk.— The results of investigation into the causation of numerous epidemics and isolated cases of contagious diseases have shown conclusively that some of these are capable of being conveyed through the agency of milk. By carelessness in cleansing dairy utensils, by feeding cows with contaminated food and watering them from stagnant or infected pools and by exposing the milk to foul and poisonous emanations, milk may become a source of danger to those who take it. Among the diseases which have been often spread in this way are the following: Tuberculosis, typhoid fever, scarlet fever, diphtheria, and so forth.

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Last Modified: Monday, 13-May-2013 15:31:46 EDT