STATISTICS AND ECONOMICS

In the United States the dairy industry has increased rapidly during the last fifty years. The average yield of milk per cow has increased nearly 100 per cent. and the total production of butter has increased nearly four times. The great change in production is largely due to the introduction of the factory system including skimming stations, butter factories and cheese factories throughout the country. These are especially abundant in New York, Wisconsin, Iowa, Ohio, Pennsylvania, Illinois, Vermont, Minnesota, Michigan and Kansas. Under factory conditions better butter and cheese can be made than on the farm, as the conditions of temperature, cleanliness, storage, etc., can be so much more readily controlled. Dairy legislation in the United States has also served to foster this industry and to protect the manufacturers of the best grades of dairy product. According to the United States census report 1,700,000,000 pounds of butter was produced in 1919.

The chief dairy countries of Europe are Denmark, Holland and Switzerland. As an illustration of the great demand that has grown up in this country for foreign cheeses, it may be stated that 11,332,304 pounds were imported from Europe in 1919, but this is only one-fourth as much as was imported before the world

war.

CHAPTER XVII

EGGS AND EGG PRODUCTS

As a convenient and concentrated form of nourishment, the eggs of various birds have been highly esteemed from the earliest times. They are similar to meat in containing proteins and fat, and also furnish an abundance of mineral matter, especially phosphates, which are so important in building up the body.

The hen's egg, which is, of course, the most important egg on the market, has an average weight of 60 grams (2 ounces), and of this the shell weighs 6 grams, the white 36 grams, and the yolk 18 grams. A duck's egg has an average weight of 70 grams and the egg of a goose usually weighs 190 grams. The shell consists mainly of calcium carbonate (89 to 97 per cent.) and is very porous. Inside the shell is a delicate membrane which incloses the egg like a sack.

Besides the eggs of the fowls mentioned, the eggs of wild birds are used1 in some countries. Plover eggs are considered a delicacy in England and Germany. The eggs of sea gulls, terns and herons have been extensively collected and used as food along the South Atlantic coast of the United States, and those of gulls and murres, on the Farallone Islands off the coast of California. As there is danger of exterminating sea birds by destroying their eggs, legislation has been enacted in many states to prevent their use as food. In the tropical sections of America turtle eggs are prized as food, and the eggs of the terrapin along the Atlantic coast. The eggs of fish, especially shad roe, and the eggs of the sturgeon preserved with salt, and known as caviar, are considered a great delicacy in many countries. (See p. 377.)

Many experiments have been made to increase the egg-produc1 U. S. Dept. Agri. Farmers' Bull. No. 128.

ing power of the hen, and also to breed hens that will lay more regularly throughout the year instead of so sparingly in winter. A hen producing more than 200 eggs a year is considered of more than average value. Although in most countries eggs are still sold by the dozen, as they differ so much in size a much fairer method would be to sell by the pound or kilo.

Amsterdam.

The fertile egg not only contains the embryo of the young chick, but it is also a storehouse for the food that it will need until sufficiently developed "to earn its living" outside the shell. As the yolk is first utilized in this growth, the embryo is in this portion of the egg. The white of the egg consists of a yellowishwhite nearly transparent, ropy liquid, which has the property

of coagulating and becoming insoluble when heated. This coagulation begins at 134° F. Enclosed within the white and "tethered by two cords" to the membrane of the white, lies the yolk, itself inclosed in a separate membrane.

Composition

The white of the egg consists of albumin-about 12 per cent.and water 85 per cent. with 2 per cent. of fat, sugar and extractives, and 1.2 per cent. of mineral matter. Nearly all the albumin is soluble in water. The yolk which is yellowish-red in tint and nearly opaque is much richer in fat than the white, and contains about fifty-one parts of water with 15 per cent. of casein and albumin and 30 per cent. of oil, lecithin and similar compounds— all very valuable nutrients. The protein of the egg yolk is believed to consist very largely of a lecithin compound, which is a nitrogenous body allied to both fats and proteins.1 Eggs also contain some phosphorous and sulfur compounds, and this accounts for the production of the ill-smelling gases, phosphine and hydrogen sulfide, when eggs decay. When eggs are brought in contact with silver the sulfur which they contain causes it to blacken on account of the formation of silver sulfide.

The composition of the whole egg as compared with meat is as follows:2

From this analysis it is evident that eggs form a valuable addition to a diet rich in carbohydrates. The combination “ham and

1 J. Am. Chem. Soc. XXII, 1900, p. 413.

• Bull. 28 Office of Exp. Sta. Ú. S. Dept. Agri.

eggs," however, is lacking in sugar and starch, and consequently is not a well-balanced ration; but "French toast" or "eggs on toast" are much nearer to a satisfactory food.

Another comparision of various foods is as follows:1

Much work has been done by physiological chemists on the digestion of eggs, as they have always been regarded as of special value in the diet of invalids and young children. The earlier experiments, which were made, however, solely upon the digestibility of eggs in the stomach, seemed to show that raw eggs required less time to digest than soft-boiled eggs, and the latter less than the hard-boiled eggs. It should be remembered, however, that with many kinds of food, the process of digestion must be completed in the intestines.

Later experiments made at the Minnesota Experiment Station seem to indicate that although the time and temperature of cooking, may have an effect on the rate of digestion, they do not materially effect the total digestibility.1 It is sometimes of importance to invalids, however, that their food be quickly digested, and the later experiments tend to confirm the general opinion that raw or soft-boiled eggs are more suitable for invalids 1 U. S. Dept. Agri. Farmers' Bull. No. 128.