Proteids, or albuminous substances.

The Proteids, because they contain the element nitrogen and the others do not, are frequently called nitrogenous, and the other two are known as non-nitrogenous substances.

The proteids, the type of which is egg albumen, or the white of egg, are found in muscle and nerve, in glands, in blood, and in nearly all the fluids of the body.

In the succeeding chapters we shall have occasion to refer to various and allied forms of proteids as they exist in muscle (myosin), coagulated blood (fibrin), and bones (gelatin).

Now it must not for one moment be supposed that the various chemical elements, as the proteids, the salts, the fats, etc., exist in the body in a condition to be easily separated one from another.

Proteids; or Nitrogenous Foods.

The proteids, frequently spoken of as the nitrogenous foods, are rich in one or more of the following organic substances: albumen, casein, fibrin, gelatine, myosin, gluten, and legumin.

As the name implies, the proteids, or nitrogenous foods, contain nitrogen; carbohydrates and fats, on the contrary, do not contain nitrogen.

The essential use of the proteids to the tissues is to supply the material from which the new proteid tissue is made or the old proteid tissue is repaired.

If our diet contained no proteids, the tissues of the body would gradually waste away, and death from starvation would result.

Oatmeal is rich in proteids.

Rice, on the other hand, contains less proteids than any other cereal grain, and is the least nutritious.

It contains about 75 per cent of water, about 20 per cent of carbohydrates, chiefly starch, 2 per cent of proteids, and a little fat and saline matters.

Proteids and fats exist only in small proportions in most vegetables, except beans and oatmeal.

As a type of the group of proteids we take the white of egg, egg-white or egg-albumen.

Nor is this all, for it also acts powerfully upon the proteids not acted upon in the stomach, and changes them into peptones that do not differ materially from those resulting from gastric digestion.

Thus it is that a certain amount of starch that has been changed into sugar, of salts in solution, of proteids converted into peptones, is taken up directly by the blood-vessels of the stomach.

Growth has ceased, the energy which induced activity is gone, and the proteids are no longer required to build up worn-out tissues.

Thus a diet habitually too rich in proteids, as with those who eat meat in excess, often over-taxes the kidneys to get rid of the excess of nitrogenous waste, and the organs of excretion are not able to rid the tissues of waste products which accumulate in the system.

Proteids (Gr. protos, first, and eidos, form).

To this classification may be added what are called albuminoids, a group of bodies resembling proteids, but having in some respects a different nutritive value.

The albuminoids closely resemble the proteids, but cannot be used like them to build up protoplasm.

[Footnote: I allude to mineral salts as found in the vegetable kingdom, not to the manufactured salts, like the ordinary table salt, etc., which are simply poisons when taken as food.] fats and oils, carbo-hydrates (starch and sugar), and proteids (the flesh and muscle-forming elements).

NITROGEN, a gaseous element which constitutes one-fourth in volume of the atmosphere, is the basis of nitric acid, and is an essential constituent of proteids, alkaloids, and albuminoids.

The doctor told him he needed carbohydrates, proteids, and above all, something nitrogenous.