Eggs consist of two edible parts; one, the white, composed of albumin, and the other, the yelk, chiefly made up of fat.

The white is a concentrated, watery solution of albumin, held together by delicate membranous meshworks. Besides the albumin it contains traces of fat, sugar, extractives and salts.

The yellow fat emulsion of the yelk contains a peculiar proteid, vitellin, some grape sugar, and some inorganic salts, in which combinations of phosphoric acid and potassium are conspicuous. Raw eggs are easy of digestion, as is all albumin in solution. Hard-boiled eggs, if not finely divided by mastication, are very difficult to digest, for the gastric juice cannot penetrate the hard masses of coagulated albumin which are so easily and commonly swallowed. Eggs, when lightly cooked, are easily digested, as the albumin is only partially coagulated, and cannot be introduced in large masses into the stomach. Eggs are of very great nutritive value, as they contain so large a percentage of proteid, fat and salts.