21.What is "Trichina?" How guarded against?21. Trichina.—It should be remembered that ham, sausages, and other forms of pork, should never be eaten in a raw or imperfectly cooked condition. The muscle of the pig is often infested by a minute animal parasite, or worm, calledtrichina spiralis. This worm may be introduced alive into the human body in pork food, where it multiplies with great rapidity, and gives rise to a painful and serious disease. This disease has been prevalent in Germany, and cases of it occur from time to time in this country.22.What part of fish is eaten? What does it resemble? Fish as food for digestion? Fish as a diet?22. Fish.—The part of fish that is eaten is the muscle, just as in the case of the meats and poultry. It closely resembles flesh in its composition, but is more watery. Some varieties are very easy of digestion, such as salmon, trout, and cod; others are quite indigestible, especially lobsters, clams, and shell-fish generally. A diet in which fish enters as the chief article, is ill adapted to strengthen mind or body, while its continued use is said to be the fertile source of nearly every form of disease of the skin. Some persons are so constituted that they can eat no kind of fish without experiencing unpleasant results.23.List of vegetable articles? Usefulness of the different vegetables? Strychnia? What further is said in relation to the nourishing and other qualities of vegetables?23. Vegetable Food.—The list of vegetable articles of diet is a very long one, including the grains from which our bread-stuffs are made, the vegetables from the garden, and the fruits. All the products of the vegetable kingdom are not alike useful. Some are positively hurtful; indeed, the most virulent poisons, as strychnia and prussic acid, are obtained from certain vegetables. Again, of sucharticles as have been found good for food, some are more nourishing than others: some require very little preparation for use, while others are hard and indigestible, and can only be used after undergoing many preparatory processes. Great care must therefore be exercised, and many experiments made, before we can arrive at a complete knowledge in reference to these articles of diet. Tea, coffee, and other substances from which drinks are made, are of vegetable origin.24.Wheat? "Staff of life?" White flour? Hard-grain wheats? Bolting? Graham bread?24. Bread.—Wheat is the principal and most valuable kind of grain for the service of man. Bread made from wheat-flour has been in use for many hundreds of years, and on this account, as well as because of its highly nourishing properties, has been aptly called "the staff of life." We never become tired of good bread as an article of daily food.The white kinds of flour contain more starch and less gluten than the darker, and are therefore less nutritious. The hard-grain wheat yields the best flour. In grinding wheat, the chaff or bran is separated by a process called "bolting." Unbolted flour is used for making brown or Graham bread.25.Leavened bread? Unleavened? Hot bread?25.The form of bread most easily digested is that which has been "leavened," or rendered porous by the use of yeast, or by some similar method. Unleavened bread requires much more mastication. Hot bread is unwholesome, because it is not firm enough to be thoroughly masticated, but is converted into a pasty, heavy mass that is not easily digested.26.Wheaten bread? Bread and butter? Experiment on the dog?26.Wheaten bread contains nearly every principle requisite for sustaining life, except fat. This is commonly added in other articles of diet, especially in butter,—"bread and butter," consequently, forming an almost perfect article offood. The following experiment is recorded: "A dog eatingad libitumof white bread, made of pure wheat, and freely supplied with water, did not live beyond fifty days. He died at the end of that time with all the signs of gradual exhaustion." Death took place, not because there was anything hurtful in the bread, but because of the absence of one or more of the food-principles.27.State what is said of the Irish potato?27. The Potato.—The common or Irish potato is the vegetable most extensively used in this country and Great Britain. Among the poorer classes in Ireland it is the main article of food. While it is not so rich in nutritious substances as many others, it has some very useful qualities. It keeps well from season to season, and men do not weary of its continuous use. It is more than two-thirds water, the balance being chiefly starch, with a little albumen.28.Sweet potato? Nightshades? Potatoes when germinating?28.The sweet potato differs from the white or common, in containing more water and a small proportion of sugar. The common potato and the tomato belong to the same botanical order as the "nightshades," but do not possess their poisonous qualities, unless we except potatoes that are in the process of germination or sprouting, when they are found injurious as food.29.Fruits? Use of ripe fruit? Nutriment they contain? Starch in unripe fruits? Cooking of unripe fruits?29. Fruits.—These are produced, in this country, in great abundance, and are remarkable alike for their variety and delicious flavor; consequently they are consumed in large quantities, especially during the warmer months. The moderate use of ripe fruits, in their season, is beneficial, because they offer a pleasant substitute for the more concentrated diet that is used in cold weather. The amount of solid nutriment they contain is, however, small. The percentage of water in cherries is seventy-five, in grapes eighty-one, in apples eighty-two. Unripe fruits contain starch, which, during the process of ripening,is converted into sugar. Such fruits are indigestible and should be avoided: cooking, however, in part removes the objections to them.30.How should drinking-water be as regards color and smell? Chemically pure water? How obtained? Agreeableness of perfectly pure water?30. Pure Water.—It is important that the water we drink and use in the preparation of food should be pure. It should be clear and colorless, with little or no taste or smell, and free from any great amount of foreign ingredients. Chemically pure water does not occur in nature: it is only obtained by the condensation of steam, carefully conducted, and is not as agreeable for drinking purposes as the water furnished by springs and streams. Rain-water is the purest occurring in nature; but even this contains certain impurities, especially the portion which falls in the early part of a shower; for in its descent from the clouds, the particles floating in the air are caught by the falling drops.31.Spring and well water? Whence the sparkle, or life? The water supply of cities? Croton water? Ridgewood?31.Water from springs and wells always contains more or less foreign matter of mineral origin. This imparts to the drink its pleasant taste—the sparkle, or "life," coming from the gases absorbed by the water during its passage under ground. The ordinary supply of cities is from some pure stream or pond conveyed from a distance through pipes, the limpid fluid containing generally only a small amount of impurity. Croton water, the supply of New York City, is very pure, and contains only four and a half grains to a gallon: the Ridgewood water of Brooklyn holds even less foreign matter.32.Impurities in drinking-water? Mineral springs?32.Drinking-water may contain as large a proportion as sixty to seventy grains per gallon of impurity, but a much larger quantity renders it unwholesome. The mineral spring waters, used popularly as medicines, are highly charged with mineral substances. Some of them, such asthe waters at Saratoga, contain three hundred grains and more to the gallon.33.What is stated of the action of water upon lead?33. Action of Water upon Lead.—The danger of using water that has been in contact with certain metals is well known. Lead is one of the most readily soluble, and probably the most poisonous of these substances in common use. When pure water and an untarnished surface of lead come in contact, the water gradually corrodes the metal, and soon holds an appreciable quantity of it in solution. When this takes place the water becomes highly injurious: the purer the water, and the more recent the use of the metal, the greater will be the danger.34.Lead in pipes and other things? Advice? What takes place after the articles of lead have been used much? What is wise?34.In cities, lead pipes are commonly used to convey water through the houses; lead being also used in the construction of roofs, cisterns, and vessels for keeping water and other liquids. After the articles of lead have been in use several months, the danger of lead-poisoning diminishes. An insoluble coating of the sulphate of lead forms upon the exposed surface, thus protecting it from further corrosion. It is, however, a wise precaution, at all times to reject the water or other fluid that has been in contact with leaden vessels over night, or for a number of hours. Allow the water in pipes to run freely before using.35.Coffee as an article of diet? Of what does it consist? How does the water affect the coffee? The peculiar stimulant? How does it affect most persons?35. Coffee.—This is an important addition to diet, and if moderately used is beneficial to persons of adult age. As commonly employed, it consists of an infusion in boiling water of the roasted and ground berry. The water extracts certain flavoring and coloring matters, but that which gives it its peculiar stimulant qualities is the alkaloidcaffein. With most persons its action is that of a gentle stimulant, without any injurious reaction. It produces a restful feeling after exhausting efforts of mind orbody; it tranquilizes, but does not disqualify for labor; and hence it is highly esteemed by persons of literary pursuits.36.Another property of coffee? Miners of Belgium? The Caravans? Among armies? Taken with meals?36.Another property of coffee is, that it diminishes the waste of the tissues, and consequently permits the performance of excessive labor upon an economical and inadequate diet. This has been tested among the miners of Belgium. Their allowance of solid food was below that found necessary in prisons and elsewhere; but, with the addition of about four pints of coffee daily, they were enabled to undergo severe labor without reducing their muscular strength. The caravans which traverse the deserts are supported by coffee during long journeys and lengthened privation of food. Among armies it is indispensable in supplementing their imperfect rations, and in relieving the sense of fatigue after great exposure and long marches. When taken with meals, coffee is also thought to promote digestion.37.Effects of tea-drinking? Peculiar principle? The tea beverage, how made? Black and green tea? Excessive use of tea or coffee?37. Tea.—The effects of tea-drinking are very similar to those of coffee, and are due to a peculiar principle calledthein. This principle is probably the same as that found in coffee,caffein, since the chemical composition of both is precisely alike. Tea, as a beverage, is made from the dried leaves of the plant by the addition of hot water; if the tea is boiled, the oil which gives it its agreeable flavor is driven off with the steam. There are two kinds of tea—the black and the green: the latter is sometimes injurious, producing wakefulness and other nervous symptoms. The excessive use of either coffee or tea will cause wakefulness.38.Experiments made during Kane's expedition?38.During Dr. Kane's expedition in the Arctic regions, the effects of these articles were compared. "Afterrepeated trials, the men took most kindly to coffee in the morning and tea in the evening. The coffee seemed to continue its influence throughout the day, and they seemed to grow hungry less rapidly than after drinking tea, while tea soothed them after a day's hard labor, and the better enabled them to sleep. They both operated upon fatigued men like a charm, and their superiority over alcoholic stimulants was very decided."39.State what is said of chocolate.39.Chocolate is made from the seeds of the cocoa-tree, a native of tropical America. Its effects resemble somewhat those of tea and coffee, but it is very rich in nutriment. Linnæus, the botanist, was so fond of this beverage, that he gave to the cocoa-tree the name,Theobroma—"the Food of the Gods." Its active principle istheobromin.40.Use of alcoholic drinks, how general? The rule given?40. Alcohol.—The list of beverages that are consumed for the sake of the alcohol they contain is a very long one. Their use is almost universally prevalent, every civilized nation, and nearly every barbarous one, having its favorite alcoholic drink; and, as a general rule, the nations which stand the highest in civilization have the greatest varieties of these beverages,—at the same time using them the most intelligently and wisely.41.The beverages produced by fermentation? The ardent spirits? Grains and fruits employed? Long use of wine? Of distilled liquors?41.The wines and malt liquors that contain a small amount of alcohol are produced by fermentation. The beverages that hold a large proportion of alcohol, the "ardent spirits," are made by distillation. Enormous quantities of grains and fruits are thus yearly diverted from their proper uses as food; some of these being corn, wheat, rye, barley, potatoes, and rice; also the grape, apple, pear, peach, sugar-cane, cherry, fig, and orange. Wine, the fermented juice of the grape, has been in use from time immemorial, while the introduction of distilled liquors dates from a comparatively recent period.42.Describe the action of alcohol upon the human system? Experience of Dr. Hayes and others?42.What is the physiological action of alcohol? Its first and most evident action is stimulation: this effect is transient, and is followed by a variable degree of depression. At first it sharpens the appetite and quickens digestion, but its habitual use impairs both. This stimulation is efficient in giving the system an artificial strength during some temporary derangement, and in enabling the endurance of unusual fatigue or exposure. The experience of Dr. Hayes, and other explorers of the polar regions, is that alcohol does not enable the body to resist the influence of cold, but, on the contrary, is always injurious.43.Another property of alcohol? How do we explain the restorative influence of wines and liquors?43.Another property it has in common with tea and coffee. It supports the powers of life, economizes food, and retards the waste of tissues; in other words, it "banks the fires," and prevents their burning wastefully. On this principle we explain the restorative influence of wines or liquors during exhausting diseases, in convalescence, and after excessive labors of mind or body.44.Alcohol, a poison? Moderate stimulants? Prevailing opinion? Hence?44.Pure alcohol, or an excessive quantity of ardent spirits, is an undoubted poison, and has been frequently known to produce fatal results. Stimulants in moderate quantities have been thought to increase strength, and in this view they have been called "alcoholic foods." This is not now conceded by scientific men. The prevailing opinion is, that they serve no useful purpose as an article of diet, and that their beneficial influence is limited to cases where the system is enfeebled, where some unnatural demand is made upon the vital powers, or where the supply of food is insufficient. Hence, while alcohol has not the power to build up, it may obstruct the process of pulling down.QUESTIONS FOR TOPICAL REVIEW.PAGE1. How is the necessity for food shown?642. To what process of waste and repair is the body constantly subjected?643. How do you account for the sensations of hunger and thirst?654. What further can you state having relation to the subject?655. What can you state in regard to the quantity of food required for the support of life?65,666. What circumstances change the needs of persons, old and young, as regards food and drink?65,677. What becomes of all the food and drink we consume?668. What further can you state in relation to the process of renovation through which the body passes?669. What can you state of the habits of nations in respect to diet?66,67,6910. What in relation to the selection of articles for food?6711. What as respects the necessity for changing or varying the diet?6712. What has been proved as regards animal food?6713. Of what importance is milk as an article of food?67,6814. What are the constituents of milk?6815. What can you state of eggs as an article of food?6816. Of the meats, so called, as an article of food?68,6917. What effect does cold have upon meats?6918. In what other way may beef and pork be preserved?6919. What can you state of salted meat as food, and of its continued use?6920. What change does meat undergo in the cooking?70,7121. What directions are given for boiling meat?7022. What for roasting, and with what results?70,7123. What is said about the frying of meats?7124. Give the statement in relation to trichina.7125. State what is said in relation to fish.7126. What is stated of the usefulness and other properties of the products of the vegetable kingdom?71,7227. What further is said of vegetable food?71,7228. Why is bread made of wheat flour so important as an article of food?7229. State whatever else you can in relation to bread.72,7330. Give the statement respecting the potato.7331. What is stated of fruits, the use of them, their nutritious qualities, etc.?73,7432. How general is the existence of perfectly pure water?7433. What is stated in relation to drinking water?74,7534. How does the action of water upon lead affect lead?7535. What further can you state on the subject?7536. What properties has coffee as an article of diet?75,7637. In what circumstances has coffee been found peculiarly beneficial?7638. What comparison is made between coffee, tea, and chocolate?7639. How are the wines, and malt and other alcoholic beverages produced?7740. What articles are employed in their production?7741. Describe the physiological action of alcohol.7842. What comparison is made between tea, coffee, and alcohol?7843. What can you state of alcohol, as a poison, a stimulant, and article of diet?7844. What, then, can be said of alcohol as a recommendation?78CHAPTER VI.DIGESTION.The Principal Processes of Nutrition—The General Plan of Digestion—Mastication—The Teeth—Preservation of the Teeth—Insalivation—The Stomach and the Gastric Juice—The Movements of the Stomach—Gastric Digestion—The Intestines—The Bile and Pancreatic Juice—Intestinal Digestion—Absorption by means of Blood-vessels and Lacteals—The Lymphatic or Absorbent System—The Lymph—Conditions which affect Digestion—The Quality, Quantity, and Temperature of the Food—The Influence of Exercise and Sleep.1.Design of food? How accomplished?1. Nutrition.—The great design of food is to givenutrimentor nourishment to the body. But this is not accomplished directly, as the food must first pass through certain preparatory changes, as follows: (1),Digestion, by which the food is reduced to a soluble condition; (2),Absorption, by which, when digested, it is imbibed into the blood; (3),Circulation, which carries the enriched blood to the various parts of the system; and (4),Assimilation, by which each tissue derives from the blood the materials necessary for its support.2.Sustaining power of food? Simile of the engine? Operation in the human body?2.By these means the sustaining power of food is gradually developed and employed, and the vital machinery kept in working order, somewhat after the manner of the steam-engine. To operate the latter, the force imprisoned within the coal and water is set free and converted into motion by the combustion of the fuel and the vaporization of the water. It will be seen, however, when we come to study these operations in the human body, that they are conducted silently and harmoniously, with marvellous delicacy and completeness, and without that friction, andconsequent loss of power, which attend the working of the most perfect machinery of man's invention.3.Change of food in digestion? Process of digestion? Describe the alimentary canal.3. General Plan of Digestion.—The great change which food undergoes in digestion is essentially a reforming process, reducing articles of diet, which are at first more or less solid, crude, and coarse, to a liquid and finely comminuted condition, suitable for absorption into the blood. The entire process of digestion takes place in what is called the alimentary canal, a narrow, tortuous tube, about thirty feet in its entire length. This canal begins in the mouth, extends thence downward through the gullet to the stomach (a receptacle in which the principal work of digestion is performed), and thence onward through the small and large intestines.Fig. 16.--Section of the Trunk.Fig. 16.—Section of the Trunk Showing the Cavities of the Chest and Abdomen.A, Cavity of Chest; B, Diaphragm; C, Abdomen; D, E, Spinal Column.4.Situation of the stomach and intestines? Action of the food? Mechanical action? Chemical?4.The stomach and intestines are situated in the cavity of the abdomen (Fig. 16, C, and Fig. 22), and occupy about two-thirds of its space. The action to which the food is subjected in these organs is of two kinds—mechanical and chemical. By the former it is crushed, agitated, and carried onward from one point to another; by the latter it is changed in form through the solvent power of the various digestive juices.5.Describe the process of mastication? How many and what movements?5. Mastication.—As soon as solid food is taken into the mouth, it undergoes mastication, or chewing. It is caught between the opposite surfaces of the teeth, and by them is cut and crushed into very small fragments. In the movements of chewing, the lower jaw plays the chief part; the upper jaw, having almost no motion, acts simply as a point of resistance, to meet the action of the former. These movements of the lower jaw are of three sorts: a vertical or cutting, a lateral or grinding, and ato-and-froor gnawing motion.Fig. 17.--Section of a Tooth.Fig. 17.—Section of a Tooth.a, Enamel;b, Cavity;c c, Roots;d, Body of the Tooth.6.Composition of the teeth? Enamel of the teeth? Interior of teeth?6.The teeth are composed of a bone-like material, and are held in place by roots running deeply into the jaw. The exposed portion, or "crown," is protected by a thin layer of enamel (Fig. 17,a), the hardest substance in the body, and, like flint, is capable of striking fire with steel. In the interior of each tooth is a cavity, containing blood-vessels and a nerve, which enter it through a minute opening at the point of the root (Fig. 19).7.The milk teeth? The permanent teeth?7.There are two sets of teeth; first, those belonging to the earlier years of childhood, called the milk teeth, which are twenty in number and small. At six or eight years of age, when the jaw expands, and when the growing body requires a more powerful and numerous set, the roots ofthe milk teeth are absorbed, and the latter are "shed," or fall out, one after another (Fig. 18), to make room for the permanent set.Fig. 18.--Section of the Jaws.Fig. 18.—Section of the Jaws.1' 2' 3' 4' 5', The Milk Teeth; 1" to 8", The Germs of the Permanent Set.8, 9.Number of teeth? How distributed?8.There are thirty-two teeth in the permanent set, as many being in one jaw as the other. Each half-jaw has eight teeth, similarly shaped and arranged in the same order: thus, two incisors, one canine, two bicuspids, and three molars. The front teeth are small, sharp, and chisel-edged, and are well adapted for cutting purposes; hence their name incisors. The canines stand next, one on each side of the jaw; these receive their name from their resemblance to the long, pointed tusks of the dog (Fig. 19).Fig. 19.--Section of the Jaws.Fig. 19.—Section of the Jaws—Right Side.V, A, N, Veins, Arteries, and Nerves of the Teeth. The root of one tooth in each jaw is cut vertically to show the cavity and the blood-vessels, etc., within it. 1 to 8, Permanent Teeth.9.The bicuspids, next in order, are larger and have a broader crown than the former; while behind them are the molars, the largest and most powerful of the entire set. These large back teeth, or "grinders," present a broad, rough surface, suitable for holding and crushing the food. The third molar, or "wisdom tooth," is the last to be cut, and does not appear until about the twenty-first year.The order of arrangement of the teeth is indicated by the following dental formula:—Human Dentition.10.Different forms of teeth? Human teeth? The inference?10.It is interesting, at this point, to notice the different forms of teeth in different animals, and observe how admirably their teeth are suited to the respective kinds of food upon which they subsist. In thecarnivora, or flesh-feeders, the teeth are sharp and pointed, enabling them both to seize their prey, and tear it in pieces; while theherbivora, or vegetable-feeders, have broad, blunt teeth, with rough crowns, suitable for grinding the tough grasses and grains upon which they feed. Human teeth partake of both forms; some of them are sharp, and others are blunt; they are therefore well adapted for the mastication of both flesh and vegetables. Hence we argue that, although man may live exclusively upon either vegetable or animal food, he should, when possible, choose a diet made up of both varieties.11.Cleaning of teeth? Effects of not cleaning?11. Preservation of the Teeth.—In order that the teeth shall remain in a sound and serviceable condition, some care is of course requisite. In the first place, they require frequent cleansing; for every time we take food, some particles of it remain in the mouth; and these, on account of the heat and moisture present, soon begin to putrefy. This not only renders the breath very offensive, but promotes decay of the teeth.12.Effects upon the saliva? Formation of tartar? How prevented? How destroyed?12.The saliva, or moisture of the mouth, undergoes a putrefactive change, and becomes the fertile soil in which a certain minute fungus has its growth. This fluid, too, if allowed to dry in the mouth, collects upon the teeth in the form of an unsightly, yellow concretion, called tartar. To prevent this formation, and to remove other offensive substances, the teeth should be frequently cleaned with water, applied by means of a soft tooth-brush. The destruction of the tartar fungus is best effected by the use of a weak solution of carbolic acid.13.Destruction of the enamel? How guarded against?13.Again, it should be borne in mind that the enamel, Nature's protection for the teeth, when once destroyed, is not formed anew; and the body of the tooth thus exposed, is liable to rapid decay. On this account, certain articles are to be guarded against; such as sharply acid substances that corrode the enamel, and hard substances that break or scratch it—as gritty tooth powders, metal tooth picks, and the shells of hard nuts. Sudden alternations from heat to cold, when eating or drinking, also tend to crack the enamel.14.Mixing of food with the saliva? What is the saliva? How secreted? The salivary glands?14. Insalivation.—When the morsel of food is cut and ground by the teeth, it is at the same time also intimately mixed with the saliva, or fluids of the mouth. This constitutes the second step of digestion, and is called insalivation. The saliva, the first of the digestive solvents, is a colorless, watery, and frothy fluid. It is secreted (i. e.separated from the blood) partly by the mucous membrane which lines the mouth; but chiefly by the salivary glands, of which there are three pairs situated near the mouth.15.The flow of saliva? The thought of food? Anxiety and grief? Animals fed upon dry and coarse food?15.These glands consist of clusters of very small pouches, around which a delicate network of blood-vessels is arranged: they empty into the mouth by means of little tubes, or ducts. The flow from these glands is at all times sufficient to maintain a soft and moist condition of the tongue and mouth; but when they are excited by the presence and taste of food, they pour forth the saliva more freely. Even the mere thought of food will at times cause the saliva to flow, as when the appetite is stimulated by the sight or smell of some savory article; so that the common expression is correct that "the mouth waters" for the favorite articles of food. Anxiety and grief prevent its flow, and cause "the tongue to cleave to the roof of the mouth." In the horse and other animals, that feed upon dry and coarse fodder, and require an abundant supply of saliva, we find large salivary glands, as well as powerful muscles of mastication.Fig. 20.--Structure of a Salivary Gland.Fig. 20.—Structure of a Salivary Gland.Fig. 21.--The Head of a Horse.Fig. 21.—The Head of a Horse, showing the large salivary gland (a), its duct (b), the muscles of mastication (c,d,e,f, andg).16.Importance of the process? The first place? The second? The third?16.The mingling of the saliva with the food seems a simple process, but it is one that plays an important partin digestion. In the first place, it facilitates the motions of mastication, by moistening the food and lubricating the various organs of the mouth. Secondly, it prepares the way for other digestive acts: by the action of the teeth, the saliva is forced into the solid food, softens the harder substances, and assists in converting the whole morsel into a semi-solid, pulpy mass, that can be easily swallowed, and readily permeated by other digestive fluids. The saliva also, by dissolving certain substances, as sugar and salt, develops the peculiar taste of each; whereas, if the tongue be dry and coated, they are tasteless. Hence, if substances are insoluble, they are devoid of taste.
21.What is "Trichina?" How guarded against?
21. Trichina.—It should be remembered that ham, sausages, and other forms of pork, should never be eaten in a raw or imperfectly cooked condition. The muscle of the pig is often infested by a minute animal parasite, or worm, calledtrichina spiralis. This worm may be introduced alive into the human body in pork food, where it multiplies with great rapidity, and gives rise to a painful and serious disease. This disease has been prevalent in Germany, and cases of it occur from time to time in this country.
22.What part of fish is eaten? What does it resemble? Fish as food for digestion? Fish as a diet?
22. Fish.—The part of fish that is eaten is the muscle, just as in the case of the meats and poultry. It closely resembles flesh in its composition, but is more watery. Some varieties are very easy of digestion, such as salmon, trout, and cod; others are quite indigestible, especially lobsters, clams, and shell-fish generally. A diet in which fish enters as the chief article, is ill adapted to strengthen mind or body, while its continued use is said to be the fertile source of nearly every form of disease of the skin. Some persons are so constituted that they can eat no kind of fish without experiencing unpleasant results.
23.List of vegetable articles? Usefulness of the different vegetables? Strychnia? What further is said in relation to the nourishing and other qualities of vegetables?
23. Vegetable Food.—The list of vegetable articles of diet is a very long one, including the grains from which our bread-stuffs are made, the vegetables from the garden, and the fruits. All the products of the vegetable kingdom are not alike useful. Some are positively hurtful; indeed, the most virulent poisons, as strychnia and prussic acid, are obtained from certain vegetables. Again, of sucharticles as have been found good for food, some are more nourishing than others: some require very little preparation for use, while others are hard and indigestible, and can only be used after undergoing many preparatory processes. Great care must therefore be exercised, and many experiments made, before we can arrive at a complete knowledge in reference to these articles of diet. Tea, coffee, and other substances from which drinks are made, are of vegetable origin.
24.Wheat? "Staff of life?" White flour? Hard-grain wheats? Bolting? Graham bread?
24. Bread.—Wheat is the principal and most valuable kind of grain for the service of man. Bread made from wheat-flour has been in use for many hundreds of years, and on this account, as well as because of its highly nourishing properties, has been aptly called "the staff of life." We never become tired of good bread as an article of daily food.
The white kinds of flour contain more starch and less gluten than the darker, and are therefore less nutritious. The hard-grain wheat yields the best flour. In grinding wheat, the chaff or bran is separated by a process called "bolting." Unbolted flour is used for making brown or Graham bread.
25.Leavened bread? Unleavened? Hot bread?
25.The form of bread most easily digested is that which has been "leavened," or rendered porous by the use of yeast, or by some similar method. Unleavened bread requires much more mastication. Hot bread is unwholesome, because it is not firm enough to be thoroughly masticated, but is converted into a pasty, heavy mass that is not easily digested.
26.Wheaten bread? Bread and butter? Experiment on the dog?
26.Wheaten bread contains nearly every principle requisite for sustaining life, except fat. This is commonly added in other articles of diet, especially in butter,—"bread and butter," consequently, forming an almost perfect article offood. The following experiment is recorded: "A dog eatingad libitumof white bread, made of pure wheat, and freely supplied with water, did not live beyond fifty days. He died at the end of that time with all the signs of gradual exhaustion." Death took place, not because there was anything hurtful in the bread, but because of the absence of one or more of the food-principles.
27.State what is said of the Irish potato?
27. The Potato.—The common or Irish potato is the vegetable most extensively used in this country and Great Britain. Among the poorer classes in Ireland it is the main article of food. While it is not so rich in nutritious substances as many others, it has some very useful qualities. It keeps well from season to season, and men do not weary of its continuous use. It is more than two-thirds water, the balance being chiefly starch, with a little albumen.
28.Sweet potato? Nightshades? Potatoes when germinating?
28.The sweet potato differs from the white or common, in containing more water and a small proportion of sugar. The common potato and the tomato belong to the same botanical order as the "nightshades," but do not possess their poisonous qualities, unless we except potatoes that are in the process of germination or sprouting, when they are found injurious as food.
29.Fruits? Use of ripe fruit? Nutriment they contain? Starch in unripe fruits? Cooking of unripe fruits?
29. Fruits.—These are produced, in this country, in great abundance, and are remarkable alike for their variety and delicious flavor; consequently they are consumed in large quantities, especially during the warmer months. The moderate use of ripe fruits, in their season, is beneficial, because they offer a pleasant substitute for the more concentrated diet that is used in cold weather. The amount of solid nutriment they contain is, however, small. The percentage of water in cherries is seventy-five, in grapes eighty-one, in apples eighty-two. Unripe fruits contain starch, which, during the process of ripening,is converted into sugar. Such fruits are indigestible and should be avoided: cooking, however, in part removes the objections to them.
30.How should drinking-water be as regards color and smell? Chemically pure water? How obtained? Agreeableness of perfectly pure water?
30. Pure Water.—It is important that the water we drink and use in the preparation of food should be pure. It should be clear and colorless, with little or no taste or smell, and free from any great amount of foreign ingredients. Chemically pure water does not occur in nature: it is only obtained by the condensation of steam, carefully conducted, and is not as agreeable for drinking purposes as the water furnished by springs and streams. Rain-water is the purest occurring in nature; but even this contains certain impurities, especially the portion which falls in the early part of a shower; for in its descent from the clouds, the particles floating in the air are caught by the falling drops.
31.Spring and well water? Whence the sparkle, or life? The water supply of cities? Croton water? Ridgewood?
31.Water from springs and wells always contains more or less foreign matter of mineral origin. This imparts to the drink its pleasant taste—the sparkle, or "life," coming from the gases absorbed by the water during its passage under ground. The ordinary supply of cities is from some pure stream or pond conveyed from a distance through pipes, the limpid fluid containing generally only a small amount of impurity. Croton water, the supply of New York City, is very pure, and contains only four and a half grains to a gallon: the Ridgewood water of Brooklyn holds even less foreign matter.
32.Impurities in drinking-water? Mineral springs?
32.Drinking-water may contain as large a proportion as sixty to seventy grains per gallon of impurity, but a much larger quantity renders it unwholesome. The mineral spring waters, used popularly as medicines, are highly charged with mineral substances. Some of them, such asthe waters at Saratoga, contain three hundred grains and more to the gallon.
33.What is stated of the action of water upon lead?
33. Action of Water upon Lead.—The danger of using water that has been in contact with certain metals is well known. Lead is one of the most readily soluble, and probably the most poisonous of these substances in common use. When pure water and an untarnished surface of lead come in contact, the water gradually corrodes the metal, and soon holds an appreciable quantity of it in solution. When this takes place the water becomes highly injurious: the purer the water, and the more recent the use of the metal, the greater will be the danger.
34.Lead in pipes and other things? Advice? What takes place after the articles of lead have been used much? What is wise?
34.In cities, lead pipes are commonly used to convey water through the houses; lead being also used in the construction of roofs, cisterns, and vessels for keeping water and other liquids. After the articles of lead have been in use several months, the danger of lead-poisoning diminishes. An insoluble coating of the sulphate of lead forms upon the exposed surface, thus protecting it from further corrosion. It is, however, a wise precaution, at all times to reject the water or other fluid that has been in contact with leaden vessels over night, or for a number of hours. Allow the water in pipes to run freely before using.
35.Coffee as an article of diet? Of what does it consist? How does the water affect the coffee? The peculiar stimulant? How does it affect most persons?
35. Coffee.—This is an important addition to diet, and if moderately used is beneficial to persons of adult age. As commonly employed, it consists of an infusion in boiling water of the roasted and ground berry. The water extracts certain flavoring and coloring matters, but that which gives it its peculiar stimulant qualities is the alkaloidcaffein. With most persons its action is that of a gentle stimulant, without any injurious reaction. It produces a restful feeling after exhausting efforts of mind orbody; it tranquilizes, but does not disqualify for labor; and hence it is highly esteemed by persons of literary pursuits.
36.Another property of coffee? Miners of Belgium? The Caravans? Among armies? Taken with meals?
36.Another property of coffee is, that it diminishes the waste of the tissues, and consequently permits the performance of excessive labor upon an economical and inadequate diet. This has been tested among the miners of Belgium. Their allowance of solid food was below that found necessary in prisons and elsewhere; but, with the addition of about four pints of coffee daily, they were enabled to undergo severe labor without reducing their muscular strength. The caravans which traverse the deserts are supported by coffee during long journeys and lengthened privation of food. Among armies it is indispensable in supplementing their imperfect rations, and in relieving the sense of fatigue after great exposure and long marches. When taken with meals, coffee is also thought to promote digestion.
37.Effects of tea-drinking? Peculiar principle? The tea beverage, how made? Black and green tea? Excessive use of tea or coffee?
37. Tea.—The effects of tea-drinking are very similar to those of coffee, and are due to a peculiar principle calledthein. This principle is probably the same as that found in coffee,caffein, since the chemical composition of both is precisely alike. Tea, as a beverage, is made from the dried leaves of the plant by the addition of hot water; if the tea is boiled, the oil which gives it its agreeable flavor is driven off with the steam. There are two kinds of tea—the black and the green: the latter is sometimes injurious, producing wakefulness and other nervous symptoms. The excessive use of either coffee or tea will cause wakefulness.
38.Experiments made during Kane's expedition?
38.During Dr. Kane's expedition in the Arctic regions, the effects of these articles were compared. "Afterrepeated trials, the men took most kindly to coffee in the morning and tea in the evening. The coffee seemed to continue its influence throughout the day, and they seemed to grow hungry less rapidly than after drinking tea, while tea soothed them after a day's hard labor, and the better enabled them to sleep. They both operated upon fatigued men like a charm, and their superiority over alcoholic stimulants was very decided."
39.State what is said of chocolate.
39.Chocolate is made from the seeds of the cocoa-tree, a native of tropical America. Its effects resemble somewhat those of tea and coffee, but it is very rich in nutriment. Linnæus, the botanist, was so fond of this beverage, that he gave to the cocoa-tree the name,Theobroma—"the Food of the Gods." Its active principle istheobromin.
40.Use of alcoholic drinks, how general? The rule given?
40. Alcohol.—The list of beverages that are consumed for the sake of the alcohol they contain is a very long one. Their use is almost universally prevalent, every civilized nation, and nearly every barbarous one, having its favorite alcoholic drink; and, as a general rule, the nations which stand the highest in civilization have the greatest varieties of these beverages,—at the same time using them the most intelligently and wisely.
41.The beverages produced by fermentation? The ardent spirits? Grains and fruits employed? Long use of wine? Of distilled liquors?
41.The wines and malt liquors that contain a small amount of alcohol are produced by fermentation. The beverages that hold a large proportion of alcohol, the "ardent spirits," are made by distillation. Enormous quantities of grains and fruits are thus yearly diverted from their proper uses as food; some of these being corn, wheat, rye, barley, potatoes, and rice; also the grape, apple, pear, peach, sugar-cane, cherry, fig, and orange. Wine, the fermented juice of the grape, has been in use from time immemorial, while the introduction of distilled liquors dates from a comparatively recent period.
42.Describe the action of alcohol upon the human system? Experience of Dr. Hayes and others?
42.What is the physiological action of alcohol? Its first and most evident action is stimulation: this effect is transient, and is followed by a variable degree of depression. At first it sharpens the appetite and quickens digestion, but its habitual use impairs both. This stimulation is efficient in giving the system an artificial strength during some temporary derangement, and in enabling the endurance of unusual fatigue or exposure. The experience of Dr. Hayes, and other explorers of the polar regions, is that alcohol does not enable the body to resist the influence of cold, but, on the contrary, is always injurious.
43.Another property of alcohol? How do we explain the restorative influence of wines and liquors?
43.Another property it has in common with tea and coffee. It supports the powers of life, economizes food, and retards the waste of tissues; in other words, it "banks the fires," and prevents their burning wastefully. On this principle we explain the restorative influence of wines or liquors during exhausting diseases, in convalescence, and after excessive labors of mind or body.
44.Alcohol, a poison? Moderate stimulants? Prevailing opinion? Hence?
44.Pure alcohol, or an excessive quantity of ardent spirits, is an undoubted poison, and has been frequently known to produce fatal results. Stimulants in moderate quantities have been thought to increase strength, and in this view they have been called "alcoholic foods." This is not now conceded by scientific men. The prevailing opinion is, that they serve no useful purpose as an article of diet, and that their beneficial influence is limited to cases where the system is enfeebled, where some unnatural demand is made upon the vital powers, or where the supply of food is insufficient. Hence, while alcohol has not the power to build up, it may obstruct the process of pulling down.
QUESTIONS FOR TOPICAL REVIEW.
CHAPTER VI.
The Principal Processes of Nutrition—The General Plan of Digestion—Mastication—The Teeth—Preservation of the Teeth—Insalivation—The Stomach and the Gastric Juice—The Movements of the Stomach—Gastric Digestion—The Intestines—The Bile and Pancreatic Juice—Intestinal Digestion—Absorption by means of Blood-vessels and Lacteals—The Lymphatic or Absorbent System—The Lymph—Conditions which affect Digestion—The Quality, Quantity, and Temperature of the Food—The Influence of Exercise and Sleep.
1.Design of food? How accomplished?
1. Nutrition.—The great design of food is to givenutrimentor nourishment to the body. But this is not accomplished directly, as the food must first pass through certain preparatory changes, as follows: (1),Digestion, by which the food is reduced to a soluble condition; (2),Absorption, by which, when digested, it is imbibed into the blood; (3),Circulation, which carries the enriched blood to the various parts of the system; and (4),Assimilation, by which each tissue derives from the blood the materials necessary for its support.
2.Sustaining power of food? Simile of the engine? Operation in the human body?
2.By these means the sustaining power of food is gradually developed and employed, and the vital machinery kept in working order, somewhat after the manner of the steam-engine. To operate the latter, the force imprisoned within the coal and water is set free and converted into motion by the combustion of the fuel and the vaporization of the water. It will be seen, however, when we come to study these operations in the human body, that they are conducted silently and harmoniously, with marvellous delicacy and completeness, and without that friction, andconsequent loss of power, which attend the working of the most perfect machinery of man's invention.
3.Change of food in digestion? Process of digestion? Describe the alimentary canal.
3. General Plan of Digestion.—The great change which food undergoes in digestion is essentially a reforming process, reducing articles of diet, which are at first more or less solid, crude, and coarse, to a liquid and finely comminuted condition, suitable for absorption into the blood. The entire process of digestion takes place in what is called the alimentary canal, a narrow, tortuous tube, about thirty feet in its entire length. This canal begins in the mouth, extends thence downward through the gullet to the stomach (a receptacle in which the principal work of digestion is performed), and thence onward through the small and large intestines.
Fig. 16.--Section of the Trunk.Fig. 16.—Section of the Trunk Showing the Cavities of the Chest and Abdomen.A, Cavity of Chest; B, Diaphragm; C, Abdomen; D, E, Spinal Column.
Fig. 16.—Section of the Trunk Showing the Cavities of the Chest and Abdomen.
A, Cavity of Chest; B, Diaphragm; C, Abdomen; D, E, Spinal Column.
4.Situation of the stomach and intestines? Action of the food? Mechanical action? Chemical?
4.The stomach and intestines are situated in the cavity of the abdomen (Fig. 16, C, and Fig. 22), and occupy about two-thirds of its space. The action to which the food is subjected in these organs is of two kinds—mechanical and chemical. By the former it is crushed, agitated, and carried onward from one point to another; by the latter it is changed in form through the solvent power of the various digestive juices.
5.Describe the process of mastication? How many and what movements?
5. Mastication.—As soon as solid food is taken into the mouth, it undergoes mastication, or chewing. It is caught between the opposite surfaces of the teeth, and by them is cut and crushed into very small fragments. In the movements of chewing, the lower jaw plays the chief part; the upper jaw, having almost no motion, acts simply as a point of resistance, to meet the action of the former. These movements of the lower jaw are of three sorts: a vertical or cutting, a lateral or grinding, and ato-and-froor gnawing motion.
Fig. 17.--Section of a Tooth.Fig. 17.—Section of a Tooth.a, Enamel;b, Cavity;c c, Roots;d, Body of the Tooth.
a, Enamel;b, Cavity;c c, Roots;d, Body of the Tooth.
6.Composition of the teeth? Enamel of the teeth? Interior of teeth?
6.The teeth are composed of a bone-like material, and are held in place by roots running deeply into the jaw. The exposed portion, or "crown," is protected by a thin layer of enamel (Fig. 17,a), the hardest substance in the body, and, like flint, is capable of striking fire with steel. In the interior of each tooth is a cavity, containing blood-vessels and a nerve, which enter it through a minute opening at the point of the root (Fig. 19).
7.The milk teeth? The permanent teeth?
7.There are two sets of teeth; first, those belonging to the earlier years of childhood, called the milk teeth, which are twenty in number and small. At six or eight years of age, when the jaw expands, and when the growing body requires a more powerful and numerous set, the roots ofthe milk teeth are absorbed, and the latter are "shed," or fall out, one after another (Fig. 18), to make room for the permanent set.
Fig. 18.--Section of the Jaws.Fig. 18.—Section of the Jaws.1' 2' 3' 4' 5', The Milk Teeth; 1" to 8", The Germs of the Permanent Set.
1' 2' 3' 4' 5', The Milk Teeth; 1" to 8", The Germs of the Permanent Set.
8, 9.Number of teeth? How distributed?
8.There are thirty-two teeth in the permanent set, as many being in one jaw as the other. Each half-jaw has eight teeth, similarly shaped and arranged in the same order: thus, two incisors, one canine, two bicuspids, and three molars. The front teeth are small, sharp, and chisel-edged, and are well adapted for cutting purposes; hence their name incisors. The canines stand next, one on each side of the jaw; these receive their name from their resemblance to the long, pointed tusks of the dog (Fig. 19).
Fig. 19.--Section of the Jaws.Fig. 19.—Section of the Jaws—Right Side.V, A, N, Veins, Arteries, and Nerves of the Teeth. The root of one tooth in each jaw is cut vertically to show the cavity and the blood-vessels, etc., within it. 1 to 8, Permanent Teeth.
V, A, N, Veins, Arteries, and Nerves of the Teeth. The root of one tooth in each jaw is cut vertically to show the cavity and the blood-vessels, etc., within it. 1 to 8, Permanent Teeth.
9.The bicuspids, next in order, are larger and have a broader crown than the former; while behind them are the molars, the largest and most powerful of the entire set. These large back teeth, or "grinders," present a broad, rough surface, suitable for holding and crushing the food. The third molar, or "wisdom tooth," is the last to be cut, and does not appear until about the twenty-first year.The order of arrangement of the teeth is indicated by the following dental formula:—
Human Dentition.
10.Different forms of teeth? Human teeth? The inference?
10.It is interesting, at this point, to notice the different forms of teeth in different animals, and observe how admirably their teeth are suited to the respective kinds of food upon which they subsist. In thecarnivora, or flesh-feeders, the teeth are sharp and pointed, enabling them both to seize their prey, and tear it in pieces; while theherbivora, or vegetable-feeders, have broad, blunt teeth, with rough crowns, suitable for grinding the tough grasses and grains upon which they feed. Human teeth partake of both forms; some of them are sharp, and others are blunt; they are therefore well adapted for the mastication of both flesh and vegetables. Hence we argue that, although man may live exclusively upon either vegetable or animal food, he should, when possible, choose a diet made up of both varieties.
11.Cleaning of teeth? Effects of not cleaning?
11. Preservation of the Teeth.—In order that the teeth shall remain in a sound and serviceable condition, some care is of course requisite. In the first place, they require frequent cleansing; for every time we take food, some particles of it remain in the mouth; and these, on account of the heat and moisture present, soon begin to putrefy. This not only renders the breath very offensive, but promotes decay of the teeth.
12.Effects upon the saliva? Formation of tartar? How prevented? How destroyed?
12.The saliva, or moisture of the mouth, undergoes a putrefactive change, and becomes the fertile soil in which a certain minute fungus has its growth. This fluid, too, if allowed to dry in the mouth, collects upon the teeth in the form of an unsightly, yellow concretion, called tartar. To prevent this formation, and to remove other offensive substances, the teeth should be frequently cleaned with water, applied by means of a soft tooth-brush. The destruction of the tartar fungus is best effected by the use of a weak solution of carbolic acid.
13.Destruction of the enamel? How guarded against?
13.Again, it should be borne in mind that the enamel, Nature's protection for the teeth, when once destroyed, is not formed anew; and the body of the tooth thus exposed, is liable to rapid decay. On this account, certain articles are to be guarded against; such as sharply acid substances that corrode the enamel, and hard substances that break or scratch it—as gritty tooth powders, metal tooth picks, and the shells of hard nuts. Sudden alternations from heat to cold, when eating or drinking, also tend to crack the enamel.
14.Mixing of food with the saliva? What is the saliva? How secreted? The salivary glands?
14. Insalivation.—When the morsel of food is cut and ground by the teeth, it is at the same time also intimately mixed with the saliva, or fluids of the mouth. This constitutes the second step of digestion, and is called insalivation. The saliva, the first of the digestive solvents, is a colorless, watery, and frothy fluid. It is secreted (i. e.separated from the blood) partly by the mucous membrane which lines the mouth; but chiefly by the salivary glands, of which there are three pairs situated near the mouth.
15.The flow of saliva? The thought of food? Anxiety and grief? Animals fed upon dry and coarse food?
15.These glands consist of clusters of very small pouches, around which a delicate network of blood-vessels is arranged: they empty into the mouth by means of little tubes, or ducts. The flow from these glands is at all times sufficient to maintain a soft and moist condition of the tongue and mouth; but when they are excited by the presence and taste of food, they pour forth the saliva more freely. Even the mere thought of food will at times cause the saliva to flow, as when the appetite is stimulated by the sight or smell of some savory article; so that the common expression is correct that "the mouth waters" for the favorite articles of food. Anxiety and grief prevent its flow, and cause "the tongue to cleave to the roof of the mouth." In the horse and other animals, that feed upon dry and coarse fodder, and require an abundant supply of saliva, we find large salivary glands, as well as powerful muscles of mastication.
Fig. 20.--Structure of a Salivary Gland.Fig. 20.—Structure of a Salivary Gland.
Fig. 21.--The Head of a Horse.Fig. 21.—The Head of a Horse, showing the large salivary gland (a), its duct (b), the muscles of mastication (c,d,e,f, andg).
16.Importance of the process? The first place? The second? The third?
16.The mingling of the saliva with the food seems a simple process, but it is one that plays an important partin digestion. In the first place, it facilitates the motions of mastication, by moistening the food and lubricating the various organs of the mouth. Secondly, it prepares the way for other digestive acts: by the action of the teeth, the saliva is forced into the solid food, softens the harder substances, and assists in converting the whole morsel into a semi-solid, pulpy mass, that can be easily swallowed, and readily permeated by other digestive fluids. The saliva also, by dissolving certain substances, as sugar and salt, develops the peculiar taste of each; whereas, if the tongue be dry and coated, they are tasteless. Hence, if substances are insoluble, they are devoid of taste.