large quantity in the cereal grains, leguminous
seeds, roots, tubers, etc., used as food), and also
by organic acids (which, as citric, malic, tartaric
acid, etc., occur in numerous vegetables employed
as food). Carbon, with hydrogen and oxygen,
occurs abundantly in the fatty group of alimentary
principles, as, for instance, in all the fat,
suet, butter, and oil that are eaten; in the oily
seeds, as nuts, walnuts, cocoanuts, etc.; and in
fatty foods, as liver, brain, etc. Phosphorus is
supplied to us by the flesh, blood, and bones used
as food, and in the form of various phosphates
it is a constituent of many of the vegetables
used as food. The system derives its sulphur
from the fibrin of flesh, the albumen of eggs,
and the casein of milk, from the vegetable fibrin
of corn, etc., from the vegetable albumen of
turnips, cauliflowers, asparagus, etc., and from the
vegetable casein of peas and beans. Most of the
culinary vegetables contain it. Chlorine and
sodium, in the form of chloride of sodium, are more
or less abundantly contained in all varieties
of animal food, and are taken separately as common
salt. Potassium is a constitutent of both
animal and vegetable food; it occurs in considerable
quantity in milk, and in the juice that
permeates animal flesh; and most inland plants
contain it. We derive the calcium of our system
from flesh, bones, eggs, milk, etc. (all of which
contain salts of lime); most vegetables also
contain lime-salts; and another source of our
calcium is common water, which usually contains
both bicarbonate and sulphate of lime. Magnesium
in small quantity is generally found in those
foods that contain calcium. Iron is a constituent
of blood found in meat; and it occurs in
smaller quantity in milk, in the yolk of egg, and
in traces in most vegetable foods. Fluorin occurs
in minute quantity in the bones and teeth,
obtained from the traces of fluorin found in milk,
blood, etc.
These simple bodies are not, however, capable of being assimilated and converted into tissue in the animal body; this combination is effected in the vegetable kingdom, and animals modify and convert the complex compounds which they obtain from vegetables. The number of combined elements varies; thus water contains only 2; sugar, starch, fat, and many organic acids contain 3; while casein, fibrin, and albumen, exclusive of the mineral salts in their ash, contain 5.
It would be impossible, and it is quite unnecessary, to mention in this article the different animals and plants that are used as food by different nations. The interested are referred to Reich's Nahrungs- und Genussmittelkunde (1860-61).
Drinks are merely liquid foods. They include:
Mucilaginous, farinaceous, or saccharine drinks—as
toast-water, barley-water, gruel, etc., which
are very slightly nutritive, and differ but little
from common water; aromatic or astringent
drinks—as tea, coffee, chocolate, and cocoa, the
last two of which contain a considerable quantity
of oil and starch; acidulous drinks—as
lemonade, ginger beer, raspberry-vinegar water;
drinks containing gelatin—the broths and soups,
which, if properly prepared, should contain all
the soluble constitutents of their ingredients;
emulsive or milky drinks—as animal milk, the
milk of the cocoanut, and almond milk, a drink
prepared from sweet almonds (animal milk
contains
all the essential ingredients of food, the
others are slightly nutritive); alcoholic and
other intoxicating drinks—including malt liquor
or beer in its various forms of ale, stout, and
porter; wines; spirits in their various forms of
brandy, rum, gin, whisky. Whether alcoholic
drinks constitute food is debatable.
Excluding salt, which must be considered as a saline alimentary principle, the most common condiments, such as mustard, capsicum (Cayenne pepper), pepper, the various spices, etc., owe their action to the presence of a volatile oil. Condiments and sauces afford little or no nutrition. They do, however, exert special action on the nervous system to stimulate secretion and also to retard tissue change and waste. Any more than a very moderate use is likely to impair the digestion and nutritive processes. Salt has a special value in promoting diffusion through the animal membranes and in bringing some of the alimentary principles into solution. Its decomposition probably furnishes the hydrochloric acid to the gastric juice. (For a general discussion of the preparation of foods, see Cookery; and in this connection see, also, Adulteration and Food.) Salted meat is, in so far as nutrition is concerned, in much the same state as meat from which good soup has been made. After flesh has been rubbed and sprinkled with dry salt, a brine is formed amounting in bulk to one-third of the fluid contained in the raw flesh. This brine is found to contain a large quantity of albumen, soluble phosphates, lactic acid, potash salts, creatin, and creatinin—substances which are essential to the constitution of the flesh, which therefore loses in nutritive value in proportion to their abstraction. For a discussion of the preservation of food, see Antiseptics; Food; and Food, Preservation of.
The method of refrigeration is, on a small scale, familiar to every one by the use of ice in the ordinary household refrigerator. (See Refrigeration.) The method of drying—evaporation of water by sun heat or in ovens—is largely applied to meats and to fruits and vegetables. Foodstuffs so treated reabsorb moisture and deteriorate after a time. Certain fruits, as raisins, figs, and dates, are very palatable after such treatment. The method of exclusion of air, sometimes called Appert's method, from its inventor (François Appert, q.v.), is applied to every kind of perishable food, and constitutes one of the great industries of the world. It consists in subjecting the article to be preserved to a temperature sufficient to destroy the germs which cause decomposition, and then putting it into tins or jars, which are immediately made air-tight. This principle is applied in the familiar ‘canning’ of vegetables and fruits. Certain special devices of limited application are resorted to, as the exclusion of air by means of oils and fats and varnishes, or a layer of paraffin.
The method of antiseptics finds application chiefly in the use of smoke, sugar, salt, alcohol, vinegar, and saltpetre.
The pecuniary economy of various foods has been the subject of much investigation in Europe and in the United States. Protein is an essential food, since from no other source can the animal obtain nitrogen; it is also much the costliest form of food. The ratios used by Atwater are 5.3 and 1 for the relative cost of protein fats and carbohydrates. It is, therefore, important
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