FOOD AND DRINK. Although nearly sixty elementary substances are known to chemists, only a comparatively small number of these take part in the formation of man and other animals; and it is only this small number of constituents which are essential elements of our food. These elements are carbon, hydrogen, nitrogen, oxy gen, phosphorus, sulphur, chlorine, sodium, potassium, calcium, magnesium, iron, and fluorine.
Carbon, hydrogen, nitrogen, and oxygen are supplied to the system by the albumin ous group of alimentary principles (see DIET)—viz., albumen, fibrine, and caseine, which occur both in the animal and vegetable kingdoms, and the gluten contained in vegetables. Animal flesh, eggs. milk, corn, and many other vegetable products, con tain one or more of these principles. The gelatinous group also introduces the same elements into the system, when such substances as preparations of isinglass, calves' feet, etc., are taken as food. Carbon, hydrogen, and oxygen are abundantly introduced into the system in the form of sugar, starch occurs in large quantity in the cereal grains, leguminous seeds, roots, tubers, etc., used as food), and organic acids (which, as citric, malic, tartaric acid, etc., occur in numerous vegetables employed as food). Car bon, with a little hydrogen and oxygen, occurs abundantly in the oleaginous group of alimentary principles, as, for instance, in all the fat, suet, butter, and oil that we eat; in the oily seeds, as nuts, walnuts, cocoa-nuts, etc.; and in fatty foods, as liver, brain, etc. Phosphorus is supplied to us by the flesh, blood, and bones used as food (the flesh of fishes is especially rich in phosphoric matter), and in the form of various phosphates, it is a constituent of many of the vegetables used as food. The system derives its sul phur from the fibrin° of flesh, the albumen of eggs, and the caseine of milk, from the vegetable fibrine of corn, etc., from the vegetable albumen of turnips, cauliflowers, asparagus, etc., and from the vegetable cascine of pease hod beans. Most of the culi
nary vegetables contain it, especially the erueiferce. Chlorine and sodium, in the form of chloride of sodium, are more or less abundantly contained in all varieties of animal food, and arc taken separately as common salt. Potassium is a constituent of both ani• inisl and vegetable food; it occurs in considerable quantity in milk, and in the juice that permeates' nimal 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 the blood found in meat; and it occurs in smaller quantity in milk, in the yoke of egg, and in traces in most vegetable foods. Fluorine occurs in minute quantity in the bones and teeth. This small is accounted for by the traces of fluorine found by Dr. George Wilson in milk, blood, etc.
These simple bodies are not, however, capable of being assimilated and converted into tissue; they must be previously combined, and this combination is primarily con ducted by the vegetable kingdom. The number of combined elements varies; thus water contains only 2; sugar, starch, fat, and many organic acids, contain 3; caseine contains 5; and fihrine and albumen contain 6.
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 subject is, however, an interesting one, and those who wish to study it may be referred to Moles chott's Physiorogie der Naltrungsmittel, 1850, and especially to Reich's .Naltrungs- and Genussmittetkunde (1860-61), which is the most learned and elaborate work on the sub ject in any language.