Hens' eggs are a complete food in the sense that they contain some of all the ingredients that are essential in foods. On account of the small quantity of carbohydrate in them, they are, however, inadequate. An average egg will yield seven grams of protein; it would, therefore, take from ten to twenty of them to supply the amount requisite for one man for one day. They are, however, among the most important articles of food, for they are bland, easily digested, and capable of being prepared in a great variety of appetizing ways.

The composition of the edible part of a hen's egg is:

The average weight of an egg is forty-four grams, and it will generate seventy calories. The white and the yolk differ considerably in composition, as the following analysis shows:

The protein of the white is commonly called egg-albumen, but it is not a simple substance. Eicholz has shown that some of the molecules contain a carbohydrate component. Fat is not found in the white of egg. In the yolk the fat consists of palmitin, stearin, olein, and such bodies as cholesterin and lecithin, which are frequently grouped with the fats because, like them, they are soluble in ether. Nuclein is one of the most important albumins of the yolk. It carries a part of the phosphorus which eggs contain. The salts in eggs are the most important ones needed by man's tissues. Moreover, they contain an assimilable iron in relatively large quantity. When cooked, the albumin of the egg is more or less coagulated. When cooked completely, it forms a firm, solid, semielastic mass that is not readily attacked by the digestive juices unless it is finely divided.

The following table compiled from Penzoldt is interesting, as it throws light upon the gastric digestibility of different culinary preparations:

Apparently this table does not accord with popular experience, which assigns the greatest digestibility to raw eggs. The observations of Burke explain the discrepancy. Raw eggs are apparently so bland that they do not excite either gastric secretion or motion, and are ultimately passed into the duodenum almost unchanged. This, of course, will not be so true if they are taken with other foods, as bouillon, or milk. Hard-boiled eggs become comparatively digestible when they are minced finely and mingled with water in the stomach. Such an egg will disappear from the stomach as quickly as a soft-boiled one.

Eggs are absorbed very completely from the intestine, leaving a residue of only about 5 per cent. Modes of Administration

Raw eggs can be given directly from the shell, or seasoned with pepper or salt, or added to bouillon, to coffee, or to milk. A very palatable preparation is made by shaking an egg thoroughly with lemon-juice and sugar, and diluting the mixture with either plain or carbonized water.

Egg-nog is made by shaking an egg with milk and flavoring the mixture with wine or distilled liquor. An agreeable, equally nutritious mixture can be made by omitting the alcoholic and flavoring with cinnamon, nutmeg, or other spice. Custards are made with egg and milk, sweetened, flavored, and cooked. These and boiled and poached eggs are the forms in which they are usually served to invalids. Eggs are, however, often used in other dishes and in cakes of various kinds.

When digestion is slow, eggs are often modified before they are completely prepared for absorption. Hydrogen sulphid and ammonia are set free from them. The former especially may escape from the stomach with other gases and be readily detected by its characteristic odor. This is always a sign that the eggs are not being perfectly digested. Somewhat similar changes take place when they spoil from long keeping. Eggs that are not fresh should never be served, and especially not to an invalid.

There are a few persons who cannot eat eggs because the eructation of sulphureted hydrogen generated by their imperfect digestion makes them distasteful. There are a few others who are made quickly and violently ill whenever they eat eggs; an idiosyncrasy that cannot be accounted for, and that has given rise to the popular expression that eggs are 'bilious.'