A Practical Physiology Part 12

119. Water. The most important natural beverage is pure water; in fact it is the only one required. Man has, however, from the earliest times preferred and daily used a variety of artificial drinks, among which are tea, coffee, and cocoa.

All beverages except certain strong alcoholic liquors, consist almost entirely of water. It is a large element of solid foods, and our bodies are made up to a great extent of water. Everything taken into the circulating fluids of the body, or eliminated from them, is done through the agency of water. As a solvent it is indispensable in all the activities of the body.

It has been estimated that an average-sized adult loses by means of the lungs, skin, and kidneys about eighty ounces of water every twenty-four hours. To restore this loss about four pints must be taken daily. About one pint of this is obtained from the food we eat, the remaining three pints being taken as drink. One of the best ways of supplying water to the body is by drinking it in its pure state, when its solvent properties can be completely utilized. The amount of water consumed depends largely upon the amount of work performed by the body, and upon the temperature.

Being one of the essential elements of the body, it is highly important that water should be free from harmful impurities. If it contain the germs of disease, sickness may follow its use. Without doubt the most important factor in the spread of disease is, with the exception of impure air, impure water. The chief agent in the spread of typhoid fever is impure water. So with cholera, the evidence is overwhelming that filthy water is an all-powerful agent in the spread of this terrible disease.

120. Tea, Coffee, and Cocoa. The active principle of tea is called theine; that of coffee, caffeine, and of cocoa, theobromine. They also contain an aromatic, volatile oil, to which they owe their distinctive flavor. Tea and coffee also contain an astringent called tannin, which gives the peculiar bitter taste to the infusions when steeped too long. In cocoa, the fat known as cocoa b.u.t.ter amounts to fifty per cent.

121. Tea. It has been estimated that one-half of the human race now use tea, either habitually or occasionally. Its use is a prolific source of indigestion, palpitation of the heart, persistent wakefulness, and of other disorders. When used at all it should be only in moderation. Persons who cannot use it without feeling its hurtful effects, should leave it alone. It should not be taken on an empty stomach, nor sipped after every mouthful of food.

122. Coffee. Coffee often disturbs the rhythm of the heart and causes palpitation. Taken at night, coffee often causes wakefulness. This effect is so well known that it is often employed to prevent sleep. Immoderate use of strong coffee may produce other toxic effects, such as muscular tremors, nervous anxiety, sick-headache, palpitation, and various uncomfortable feelings in the cardiac region. Some persons cannot drink even a small amount of tea or coffee without these unpleasant effects.

These favorite beverages are unsuitable for young people.

123. Cocoa. The beverage known as cocoa comes from the seeds of the cocoa-tree, which are roasted like the coffee berries to develop the aroma. Chocolate is manufactured cocoa,--sugar and flavors being added to the prepared seeds. Chocolate is a convenient and palatable form of highly nutritious food. For those with whom tea and coffee disagree, it may be an agreeable beverage. The large quant.i.ty of fat which it contains, however, often causes it to be somewhat indigestible.

124. Alcoholic Beverages. There is a cla.s.s of liquids which are certainly not properly food or drink, but being so commonly used as beverages, they seem to require special notice in this chapter. In view of the great variety of alcoholic beverages, the prevalence of their use, and the very remarkable deleterious effects they produce upon the bodily organism, they imperatively demand our most careful attention, both from a physiological and an hygienic point of view.

125. Nature of Alcohol. The ceaseless action of minute forms of plant life, in bringing about the decomposition of the elaborated products of organized plant or animal structures, will be described in more detail (secs. 394-398).

All such work of vegetable organisms, whether going on in the moulding cheese, in the souring of milk, in putrefying meat, in rotting fruit, or in decomposing fruit juice, is essentially one of fermentation, caused by these minute forms of plant life. There are many kinds of fermentation, each with its own special form of minute plant life or micro-organism.

In this section we are more especially concerned about that fermentation which results from the decomposition of sweet fruit, plant, or other vegetable, juices which are composed largely of water containing sugar and flavoring matters.

This special form of fermentation is known as alcoholic or vinous fermentation, and the micro-organisms that cause it are familiarly termed alcoholic ferments. The botanist cla.s.ses them as _Saccharomycetes_, of which there are several varieties. Germs of _Saccharomycetes_ are found on the surfaces and stems of fruit as it is ripening. While the fruit remains whole these germs have no power to invade the juice, and even when the skins are broken the conditions are less favorable for their work than for that of the moulds,[18] which are the cause of the rotting of fruit.

But when fruit is crushed and its juice pressed out, the _Saccharomycetes_ are carried into it where they cannot get the oxygen they need from the air. They are then able to obtain oxygen by taking it from the sugar of the juice. By so doing they cause a breaking up of the sugar and a rearrangement of its elements. Two new substances are formed in this decomposition of sugar, viz., carbon dioxid, which arises from the liquid in tiny bubbles, and alcohol, a poison which remains in the fermenting fluid.

Now we must remember that fermentation entirely changes the nature of the substance fermented. For all forms of decomposition this one law holds good. Before alcoholic fermentation, the fruit juice was wholesome and beneficial; after fermentation, it becomes, by the action of the minute germs, a poisonous liquid known as alcohol, and which forms an essential part of all intoxicating beverages.

Taking advantage of this great law of fermentation which dominates the realm of nature, man has devised means to manufacture various alcoholic beverages from a great variety of plant structures, as ripe grapes, pears, apples, and other fruits, cane juices, corn, the malt of barley, rye, wheat, and other cereals.

The process differs according to the substance used and the manner in which it is treated, but the ultimate outcome is always the same, viz., the manufacture of a beverage containing a greater or less proportion of alcoholic poison. By the process of _distillation_, new and stronger liquor is made. Beverages thus distilled are known as ardent spirits. Brandy is distilled from wine, rum from fermented mola.s.ses, and commercial alcohol mostly from whiskey.

The poisonous element in all forms of intoxicating drinks, and the one so fraught with danger to the bodily tissues, is the alcohol they contain. The proportion of the alcoholic ingredient varies, being about 50 per cent in brandy, whiskey, and rum, about 20 to 15 per cent in wines, down to 5 per cent, or less, in the various beers and cider; but whether the proportion of alcohol be more or less, the same element of danger is always present.

126. Effects of Alcoholic Beverages upon the Human System. One of the most common alcoholic beverages is wine, made from the juice of grapes. As the juice flows from the crushed fruit the ferments are washed from the skins and stems into the vat. Here they bud and multiply rapidly, producing alcohol. In a few hours the juice that was sweet and wholesome while in the grape is changed to a poisonous liquid, capable of injuring whoever drinks it. One of the gravest dangers of wine-drinking is the power which the alcohol in it has to create a thirst which demands more alcohol. The spread of alcoholism in wine-making countries is an ill.u.s.tration of this fact.

Another alcoholic beverage, common in apple-growing districts, is cider.

Until the microscope revealed the ferment germ on the "bloom" of the apple-skin, very little was known of the changes produced in cider during the mysterious process of "working." Now, when we see the bubbles of gas in the gla.s.s of cider we know what has produced them, and we know too that a poison which we do not see is there also in corresponding amounts. We have learned, too, to trace the wrecked hopes of many a farmer's family to the alcohol in the cider which he provided so freely, supposing it harmless.

Beer and other malt liquors are made from grain. By sprouting the grain, which changes its starch to sugar, and then dissolving out the sugar with water, a sweet liquid is obtained which is fermented with yeast, one kind of alcoholic ferment. Some kinds of beer contain only a small percentage of alcohol, but these are usually drunk in proportionately large amounts.

The life insurance company finds the beer drinker a precarious risk; the surgeon finds him an unpromising subject; the criminal court finds him conspicuous in its proceedings. The united testimony from all these sources is that beer is demoralizing, mentally, morally, and physically.

127. Cooking. The process through which nearly all food used by civilized man has to pa.s.s before it is eaten is known as cooking.

Very few articles indeed are consumed in their natural state, the exceptions being eggs, milk, oysters, fruit and a few vegetables. Man is the only animal that cooks his food. Although there are savage races that have no knowledge of cooking, civilized man invariably cooks most of his food. It seems to be true that as nations advance in civilization they make a proportionate advance in the art of cooking.

Cooking answers most important purposes in connection with our food, especially from its influence upon health. It enables food to be more readily chewed, and more easily digested. Thus, a piece of meat when raw is tough and tenacious, but if cooked the fibers lose much of their toughness, while the connective tissues are changed into a soft and jelly-like ma.s.s. Besides, the meat is much more readily masticated and acted upon by the digestive fluids. So cooking makes vegetables and grains softer, loosens their structure, and enables the digestive juices readily to penetrate their substance.

Cooking also improves or develops flavors in food, especially in animal foods, and thus makes them attractive and pleasant to the palate. The appearance of uncooked meat, for example, is repulsive to our taste, but by the process of cooking, agreeable flavors are developed which stimulate the appet.i.te and the flow of digestive fluids.

Another important use of cooking is that it kills any minute parasites or germs in the raw food. The safeguard of cooking thus effectually removes some important causes of disease. The warmth that cooking imparts to food is a matter of no slight importance; for warm food is more readily digested, and therefore nourishes the body more quickly.

The art of cooking plays a very important part in the matter of health, and thus of comfort and happiness. Badly cooked and ill-a.s.sorted foods are often the cause of serious disorders. Mere cooking is not enough, but good cooking is essential.

Experiments.

Experiments with the Proteids.

Experiment 31. As a type of the group of proteids we take the white of egg, egg-white or egg-alb.u.men. Break an egg carefully, so as not to mix the white with the yolk. Drop about half a teaspoonful of the raw white of egg into half a pint of distilled water. Beat the mixture vigorously with a gla.s.s rod until it froths freely. Filter through several folds of muslin until a fairly clear solution is obtained.

Experiment 32. To a small quant.i.ty of this solution in a test tube add strong nitric acid, and boil. Note the formation of a white precipitate, which turns yellow. After cooling, add ammonia, and note that the precipitate becomes orange.

Experiment 33. Add to the solution of egg-alb.u.men, excess of strong solution of caustic soda (or potash), and then a drop or two of very dilute solution (one per cent) of copper sulphate. A violet color is obtained which deepens on boiling.

Experiment 34. Boil a small portion of the alb.u.men solution in a test tube, adding drop by drop dilute acetic acid (two per cent) until a flaky coagulum of insoluble alb.u.men separates.

Experiments with Starch.

Experiment 35. Wash a potato and peel it. Grate it on a nutmeg grater into a tall cylindrical gla.s.s full of water. Allow the suspended particles to subside, and after a time note the deposit. The lowest layer consists of a white powder, or starch, and above it lie coa.r.s.er fragments of cellulose and other matters.

Experiment 36. Examine under the microscope a bit of the above white deposit. Note that each starch granule shows an eccentric hilum with concentric markings. Add a few drops of very dilute solution of iodine.

Each granule becomes blue, while the markings become more distinct.

Experiment 37. Examine a few of the many varieties of other kinds of starch granules, as in rice, arrowroot, etc. Press some dry starch powder between the thumb and forefinger, and note the peculiar crepitation.

Experiment 38. Rub a few bits of starch in a little cold water. Put a little of the mixture in a large test tube, and then fill with boiling water. Boil until an imperfect opalescent solution is obtained.

Experiment 39. Add powdered dry starch to cold water. It is insoluble. Filter and test the filtrate with iodine. It gives no blue color.

Experiment 40. Boil a little starch with water; if there is enough starch it sets on cooling and a paste results.

Experiment 41. Moisten some flour with water until it forms a tough, tenacious dough; tie it in a piece of cotton cloth, and knead it in a vessel containing water until all the starch is separated. There remains on the cloth a grayish white, sticky, elastic "gluten," made up of alb.u.men, some of the ash, and fats. Draw out some of the gluten into threads, and observe its tenacious character.

Experiment 42. Shake up a little flour with ether in a test tube, with a tight-fitting cork. Allow the mixture to stand for an hour, shaking it from time to time. Filter off the ether, and place some of it on a perfectly clean watch gla.s.s. Allow the ether to evaporate, when a greasy stain will be left, thus showing the presence of fats in the flour.

Experiment 43. Secure a specimen of the various kinds of flour, and meal, peas, beans, rice, tapioca, potato, etc. Boil a small quant.i.ty of each in a test tube for some minutes. Put a bit of each thus cooked on a white plate, and pour on it two or three drops of the tincture of iodine.

Note the various changes of color,--blue, greenish, orange, or yellowish.

Experiments with Milk.

Experiment 44. Use fresh cow's milk. Examine the naked-eye character of the milk. Test its reaction with litmus paper. It is usually neutral or slightly alkaline.

Experiment 45. Examine with the microscope a drop of milk, noting numerous small, highly refractive oil globules floating in a fluid.