NATURE OF THE FOOD SUPPLIED TO THE HUMAN the organic elements, such as salt and the other

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mineral matters. They may be called nitroLL the substances that are found in genous, non-nitrogenous, and mineral foods. the bodies of animals, and also of These substances are not, however, supplied plants, are supplied from without. separately, but are all contained in varying proThe cells of which plants and ani- portions in the food we eat. Thus, bread conmals are composed absorb the mat-tains the nitrogenous principle fibrine, and the ters of which they consist from the world around non-nitrogenous principle starch, whilst all them, and these matters are called their food. kinds of meat contain fibrine, and the nonPlants differ from animals in absorbing their nitrogenous principle fat. In addition to the food by their surface, whilst most animals have three groups of substances now mentioned, an internal bag or stomach, from the inside of there must be water in all kinds of food. As which the food is taken up; and there is an we have seen, three fourths of the human body orifice leading to this bag called a mouth. The consists of water, and as the food supplied to food of the plant is also different from that of the body must be like the substances of which the animal. The plant takes up mineral sub- the body is formed, a large quantity of water stances, the chief of which are carbonic acid must be taken in food. and ammonia, whilst animals take up substances which are formed in the tissues of plants. The life of the plant depends on its changing mineral substances into organic compounds, whilst the life of the animal consists in changing organic compounds into mineral matters. The life of the plant ends where that of the animal begins, and the life of the plant begins where that of the animal ends. Animals, in dying, give out the carbonic acid and ammonia, on which plants feed. Carbonic acid and ammonia contain the four organic elements-carbon and oxygen in the first, and nitrogen and hydrogen in the last.

Animals obtain the principal part of their food from plants; and when they feed on animals, as man feeds on sheep and oxen, the animals they eat have obtained their flesh from the vegetable kingdom. If regard is had to what man takes, it will be found that all his food may be included in three great classes.

The necessity for the supply of food to the body arises out of the fact that the life of man depends on the continued use and destruction of the particles of which the body is composed. If a man sits at one end of a pair of scales, and puts weights at the other, he will find that the longer he sits the lighter he grows. Whilst he moves, breathes, thinks, or feels, certain portions of his body are being converted into gas and liquids, which principally pass from his lungs and kidneys. Now this loss must be supplied. The loss is sustained by every part of the body, and food is taken to supply the loss.

The loss sustained by the body during life is due to two causes. First, the action of the muscles and nerves in sustaining life consume certain particles of the body, which having been used are cast off from it by the lungs and kidneys. It is by this burning or consuming that the human body, like that of other animal bodies,

has a temperature above that of the surrounding starch is taken as food the carbon alone is atmosphere, which is called animal heat. Thus chemically changed. Starch, although insoluble the body of a human being in health is always in water, is easily diffused through it, and when kept at a temperature of ninety-eight degrees of heated with water mixes with it and forms a a Fahrenheit's thermometer. Other animals thickened compound. Hence, when flour is maintain other temperatures, and their heat is boiled in water it thickens, and thus puddings mainly due to the burning in the blood of the and dumplings are made. Arrowroot, tapioca, food they eat in contact with the atmosphere sago, and corn-flour, which is made from maize, which they breathe. According as the sub-consist principally of starch, and form thickened stances of the food are used for these two pur-compounds when heated with water. Starch is poses they are called flesh-forming and heat or not taken up into the blood in its natural form, force-giving. Though the flesh-formers can but is converted into sugar in the mouth by the also supply force, and are necessary from time to action of the saliva. Hence the importance of time to assist the force or heat-givers-yet the allowing all foods containing starch to remain in heat-givers can not alone form flesh or help in the mouth for a little time before they are forming it, since they have no nitrogen. swallowed.

The flesh-forming principles of the food are Sugar has the same general composition as known by the names albumen, gluten, and starch. It is, however, soluble in water, and casein, and are contained in vegetable as well as when taken into the stomach is readily absorbed animal foods. A sort of albumen, called gluten, and taken into the blood. It has two forms, is contained in the flour of wheat, in barley, which are called cane-sugar and fruit-sugar. oats, maize, potatoes, and other kinds of vege- They both act alike on the system. Fruit-sugar table food. Another sort of albumen, called is found in fruits, and is especially contained in sometimes fibrine, constitutes the principal part the fruits of plants, as grapes, figs, plums, pears, of the flesh of animals, and is obtained from and other sweet fruits. Cane-sugar is crystaldead blood. Other varieties of albumen are lizable, and is separated from the sugar cane, also found in small quantities in various kinds beet, maple, and other plants, for dietetical use ; of vegetable food, but more especially in the all the sugar ordinarily employed for food and white of eggs, in the blood of animals, and in the manufacture of sweetmeats is of this kind. the nervous system of animals. All albumens Sugar is contained in small quantities in all coagulate by exposure to heat, and this property kinds of vegetable food. Fruit-sugar undergoes is familiarly known by the hardening during the process known by the name of fermentation, boiling of the white" of the egg. Casein is by which the sugar loses a certain quantity of found in peas, beans, and lentils in the vegetable carbonic acid, and is converted into the comkingdom, where it exists in larger quantities pound known by the name of alcohol. than either gluten or the other albumens in other vegetable foods. It is also found in milk, and cheese when separated from milk consists principally of casein.

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The other force or heat-giving substance is fat. In this term is included all those substances which are called by the names of oil, snet, tallow, grease, butter, and lard. They all All these substances contain carbon, which contain compounds having the same general may be separated, and is capable of giving out nature, and consisting principally of carbon and heat and other forces by uniting in the system hydrogen, with a small quantity of oxygen. with oxygen, but the non-nitrogenous substances Although not soluble in water fat is rendered contain larger quantities of carbon, and are soluble in the stomach during the process of especially employed in the generation of heat digestion, and is thus taken into the system. and other forms of force in the body. The It acts in two ways on the system. First, like force-giving substances are starch, sugar, and starch and sugar, it assists in maintaining fat. Starch is especially a vegetable product, animal heat, moving and nerve-power, and in and is found almost universally present in vege- the performance of this function it acts more table substances. Wheaten flour contains efficiently than either starch or sugar, as not sixty parts in the hundred of starch; barley only is the carbon burned in the system but and oats contain it in the same proportion, also the hydrogen. As far as this function whilst rice contains at least eighty parts in the goes, one pound of butter or lard will give out one hundred. Potatoes consist largely of water, as much heat as two pounds and a half of but possess twenty-five parts in the hundred of starch or sugar. A second function of fat is starch. Starch contains no nitrogen, and con- that it is deposited in the body, and forms what sists in every twenty-one parts by volume of six is called adipose tissue or fat. A certain quanof carbon, and five of oxygen, and ten of hydro-tity of fat is essential to the constitution of the gen. The two last elements exist in the same body, and without it the system is not properly quantities in which they form water, and when nourished. So essential is fat to the body that

in certain diseases-as consumption-where it only substance besides water which is taken in is not found in proper quantities, cod-liver oil a mineral form as food. It is used alike by the and other fatty compounds are given for the rich and poor. The animal world needs it as purpose of making people fatter. Fat is well as man, and interesting records have been obtained as food from both the vegetable and given by naturalists of the pilgrimage made by animal kingdoms. Salad oil is a familiar in- animals to the sea-shore or to salt lakes for the stance of the former, whilst all animal food purpose of procuring this necessity of their contains it in larger or smaller quantities. existence. Amongst the ashes is found potasPork contains more fat than mutton, and sium. Although it exists in less quantities mutton than beef. than the metals of lime or soda, it nevertheless

All food contains saline substances. If we seems to act a very important part in the sysburn a portion of the flesh of any animal we tem. Whilst common salt is found in the may drive off the carbon, oxygen, hydrogen, blood, the salts of potassium are found in the and nitrogen, and ashes" are left. These flesh. One of the consequences of a diet conashes are the saline and mineral constituents of sisting of salt meat is scurvy. In meat preserved the animal. They exist in the blood and by salting, the chloride of sodium is made to tissues, and are as essential to the life of the take the place of the salts of potash, and in this animal as the other products. Like the ele- way a proper supply of potash is not afforded to ments contained in the other compounds, they the system. Our sailors in the navy formerly are constantly being carried off from the body, suffered very greatly from scurvy, but since the and need to be renewed in the food. Whilst introduction of lime-juice, or preserved vegefood is being cooked, especially in boiling, these tables, as a part of their diet, the disease is now saline matters may be lost. Care should be seldom seen. The most efficient cure for taken to supply them in the form of uncooked scurvy is fresh vegetables of any kind, and as it food. Water, milk, fresh vegetables, as salads is known that they contain considerable quanand uncooked fruits, are all means of supplying tities of the salts of potash, it is inferred that these compounds to the system. One of the they cure this disease by supplying this necesmost important of these compounds is phosphate sary substance to the blood. Whether the of lime. This substance enters into the com- salts of potash supplied in any other form position of the bones, of which it forms forty would be as beneficial has not been tried, but per cent. When it is deficient, the bones are there can be little doubt that the habitual use soft and unable to resist the action of the of uncooked fruit or vegetables in the form of muscles attached to them, and persons thus salad is a valuable means of maintaining health. afflicted become more or less deformed. The There is yet another mineral substance found in deficiency of this substance is a characteristic the human body the presence of which, though feature of some diseases, and its administration in small quantities, is most essential, to health, medicinally has been found very beneficial. It and that is iron. That this metal exists in the is contained in wheat, barley, oats, and rye, and human body is attested by the somewhat from these sources the chief supply of it to the melancholy experiment practiced by those who human body is derived. These plants require advocate the ancient practice of burning, and phosphate of lime for their growth and the per- who, instead of preserving the ashes of their fecting of their grains: hence it is supplied friends in appropriate urns, have extracted artificially by the farmer. The knowledge of from them the few grains of iron they contain, the method of procuring and preparing this and worn it in the form of a memorial ring. substance for manure is one of the triumphs of The absence of iron from the body is indicated modern chemistry, and has been the means of by certain well-known symptoms, as paleness of increasing and cheapening the supplies of corn for the sustenance of man. A diet deficient in substances yielding the phosphate of lime is injurious to man, and should be avoided. It is on this as well as on other accounts that a diet Besides the foregoing substances, the system comprising bread made from wheat flour forms seems to require the addition to food, in small the food of the strongest and most vigorous quantities, of those materials which are known races of mankind. Another mineral substance by the name of condiments and spices. They found in the body is chloride of sodium-com- act upon the nervous system, and seem to stimmon salt. The quantity contained in a body ulate the stomach to produce those changes in weighing 154 pounds is three ounces and three food which are necessary to its digestion and quarters. So important is this substance to preparation to convert it into blood. In this health that serious diseases have been known way salt seems to act as a condiment. Mustard to be produced by its being withheld. It is the and pepper, onions, sage, and thyme, are all

the face and lips, palpitation of the heart, and general weakness; and this state of the system is only to be remedied by the administration of doses of iron in a medicinal form.

in containing large quantities of fat. Cocoapaste contains half its weight of fat, and also a certain quantity of albumen. It is on this account that cocoa may be regarded as a substantive article of diet. It contains less of the active principle than either coffee or tea. Cocoa and chocolate are the same thing, but the latter term is used when the seeds of the cocoa are ground into a paste, and vanilla is added to flavor the compound.

used in the same way. Nutmegs, cinnamon, and much by the use of one as the other; and coffee, cloves, which are eaten with sugar, act in the like tea, may be taken to excess. Coffee also same manner, and are known as spices. There contains volatile oils, and an acid, which gives is no doubt, also, that small quantities of it its flavor; but it contains no tannin. alcohol taken with food act similarly, and is the Chocolate, or cocoa, differs from tea and coffee foundation of the pernicious practice of taking alcohol for the sake of its intoxicating effect. Alcohol, which is the product of the fermentation of sugar, acts as a powerful stimulant on the nervous system. It is the basis of wines, beers, and distilled spirits, and is one of the most dangerous articles of food. When taken in large quantities, in any of the above forms, it acts most injuriously on the stomach, liver, brain, heart, and other organs of the body. So destructive is the effect of this agent on the The foregoing substances enter more or less whole body that large numbers of persons avoid largely into the daily food of man. Great as is its use altogether, and thus have successfully the variety of food which he takes, each form of demonstrated that the use of this agent is not food is capable of being analyzed, and the necessary to health. If, however, it is employed, quantity of flesh-formers, force-giving, and it should not be taken without other kinds of mineral matters that it contains ascertained. food, as, even diluted in the form of beer or The quantity of those substances required by wine, it is found to act injuriously on the deli- man must vary according to age, sex, climate, cate membranes of the stomach and other size, health, and daily work. The young of digestive organs. When taken in quantities the mammalia are all fed for some months after beyond that required to act as a healthy stimulus their birth by milk. This liquid contains all to the nervous system, it is found to destroy the the substances necessary to a healthy diet. In quality of the blood, to congest the membranes one hundred pounds of milk there are five of the brain, to produce incurable affections of pounds of casein, three pounds and a half of the liver and kidneys, and to effect changes in the muscular structure of the heart, the result of all of which are painful and lingering diseases, or sudden death.

butter, four pounds and a half of sugar, and one pound of mineral matters; the rest is water. The milk of all animals may be used as food by man; and although it is the especial There is another group of substances taken food of infants, it is an excellent addition to the as food, of which we must take notice, and food of man at all ages. Butter is separated these are tea, coffee, and chocolate. Although from milk, and used as a separate article of the leaves of tea and the seeds of coffee and diet, whilst the casein and water are separated chocolate have a very different composition, by the name of cheese. The casein is less they all agree in containing an active principle digestible in this form than in milk, but neverwhich acts powerfully on the nervous system. theless cheese is a highly nutritious article of This principle is called theine in tea, caffeine diet, and may be employed with great advantage in coffee, and theobromine in chocolate. It is as an addition to daily food. It is difficult to absolutely identical in tea and coffee, and only estimate the quantity of food that a human differs slightly in chocolate. Tea contains, being ought to take in a day. A healthy infant besides theine, volatile oils, which give to it its of six months old will consume from one quart peculiar flavor, and also tannin an astringent sub- to three pints of cows' milk. An average man, stance. Strong tea acts injuriously on the weighing one hundred and fifty-four pounds, is nerves, and, when taken of the usual strength, found to consume in a day four ounces of flesh it is apt to interfere with the digestion of meat, formers, twelve ounces of starch, five ounces of on account of the tannin coagulating the albu- butter and fat, two ounces of sugar, and one ounce of mineral matter. This will give a fair Tea is best taken with milk and sugar, as is the usual practice of England; but it idea of the average quantity of solid food should be recollected that, whilst small quan- required by man. When men work hard they tities of this beverage, like alcoholic beverages, require more food, and persons taking but little may be taken with impunity, that large quan- exercise require less than those who take a great tities interfere with healthy digestion, and lay the deal. Growing boys and girls, between twelve foundation of serious disease. Coffee contains and eighteen years of age, require more food less theine than tea, but as larger quantities of the roasted seeds are used than of tea to form a beverage, the nervous system is acted on as

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than grown-up men and women, as they not only need food to perform the functions of life, but also food to permit of the growth of the various organs of their body.