plied that they now number more than a hundred in Europe alone; and in these and in the laboratories of the great universities, analyses have been made of most of the foods used by men and animals and also tests of the relative flesh and fat producing power of different foods and combinations of foods.

For years the results of these investigations have been applied with profit to the feeding of cattle, but it was a case of threatened wholesale starvation in England that first turned the attention of properly trained persons to a like study of the nourishment of human beings. During our Civil War the condition of the cotton spinners in Lancashire and Cheshire, England, became so serious as to make government help necessary to keep them from starving, and in 1862 and 1863 Dr. Edward Smith was commissioned to examine into the dietetic needs of the distressed operatives. In his report for 1863 are found tables of the food consumed per week by 634 families, and in spite of the difficulties standing in the way of such an investigation, the foods consumed were classified into tables showing the amounts of the different food principles taken per week by each family.

One of the great practical results following from this investigation was the determination of the minimum amount of each nutritive principle which men, women and children need, to keep them in fair health. The amount of food with which an unemployed man can fight off starvation, and the diseases temporarily incident to it, was found to be represented in 35 ounces of good bread per day, and the necessary amount of wholesome water.

Since the publication of Dr. Smith's report similar inquiries have been instituted by the scientists of other countries, and many analyses have been made of the exact amount and kinds of food eaten by various classes of laborers under the most varied conditions. Professors Voit and Pettenkofer of Munich have even accounted for every particle of food that passed through the body of a man, both while he was at work and while he was idle. They have also noted how much of his own body was consumed when he ate nothing. Finally a great number of averages have been taken and so-called "standard dietaries" constructed, by which is meant the average amount of each of the chief food principles that keep an average muscle-worker in good condition, when doing average work.

Every one will admit that it is of great importance for the farmer to know in what proportion he shall lay in hay and other food for

the winter feeding of his stock; the animals must thrive, but there must be no waste by furnishing food in the wrong quantities or proportions.

For the housewife, the food question in its relation to her family can be stated in the very same words. It is important that she should economize, but her path will be full of pitfalls if she does not understand in what true economy consists Most people with a real interest in this subject, have had at some period of their lives certain pet theories as to food. Perhaps they have been at one time convinced that most people ate too much, at another, that meat was the all strengthener, or they may have been afflicted with the vegetarian fad, and whatever their special views have been they have thought that they rested them upon facts. But surely they would never have pinned their faith to one-sided diets if they had rightly comprehended the main facts of nutrition We believe that if these facts as at present interpreted, and the world's experience in applying them, can be put at the command of the housewife, she can use them to great profit.

We have employed the term "food principles"; what do we mean by it? Everyone knows what is meant by a food, as meat or bread, and everyone knows that the food offered us by our butchers and grocers comes from the animal and vegetable kingdoms. The oxygen we breathe and the water we drink nature furnishes for us directly, so to speak, though unfortunately for many of us, and especially for young children, the former is not thought of as a food. Oxygen aside, it has been found by those who have studied the matter, that all foods contain one or more of five classes of constituents, call "nutritive ingredients" or "food principles." These five principles are:

(1) Water.

(2) Proteids.

(3) Fats.

(4) Carbohydrates.

(5) Salts or mineral constituents.

WATER.

It is important to note that our bodies when full-grown are twothirds water, and our food contains from 1 to 94 per cent of it. Considering the scope of this essay, it must be left to take care of itself as a food.

PROTEIDS.

A class of nearly allied bodies is included under this head. The whole class is sometimes called "Albumens."

The housewife is familiar with proteids in such foods as the lean

of meat, in eggs and cheese. These contain the principle in various proportions; for example,

Vegetables are more deficient in proteids though the grains and

legumes contain much of it.

Wheat flour has.

10 to 12 per ct.

Peas, beans and Lentils have

22.85 to 27.7 66 .6

In fresh vegetables we find only from to 3 per cent, excepting green peas and beans in which the proteids reach 5 to 6.5 per cent.

FATS.

Fats are obtained from both the animal and vegetable kingdoms. Those used by us in cookery come mostly from animals, and are known to the housewife as butter, lard and tallow. Vegetable food as a rule, is very poor in fats, containing from 0 to 3 per cent. only. Some of the cereals, like corn and oats contain from 4 to 7 per cent. of fats.

CARBOHYDRATES.

The bodies classed as "carbohydrates" are found mainly in vegetables. The housekeeper knows them as starches and sugars.

Under the starches proper are included such things as the starches of grains and seeds, Iceland moss, gums and dextrin.

Milk is one of the few animal products that has more than a very small quantity of carbohydrates. It contains on the average about 4.8 per cent. of this principle;-slightly more than of either proteids or fats.

SALTS.

The things that give hardness to our bones, like calcium phosphate, and the common salt with which we flavor our food, illustrate this class.

FUNCTIONS OF FOOD PRINCIPLES.

To know in what proportion these food principles should be represented in our diet, we must inquire into the part played by each of them in the body. The first and the last principle may be dismissed briefly. The former, water, is the great medium which floats things through the body; the latter, salts, are combined in various ways with the solids and fluids of our foods, and we shall not easily suffer from lack of them.

The other three food principles (let us call them in the following pages the three great food principles), cannot be so summarily dealt with. We might say, briefly and dogmatically, that the proteids are flesh foods," the fats are "heat foods,' the carbohydrates "work foods." To be sure, experimenters are agreed on the main points, but the different schools are still at war on the final explanations and on many details, and it has become more and more evident that we cannot portion off the work of the body in this simple style. Though each of the three great food principles can be said to have a favorite part which it plays better than any other, yet we find that like an actor of varied talents, it has more than one rôle in its repertoire.

FUNCTION OF PROTEIDS.

That this class is indispensable we have the best of proofs. It must be given us in one or another of its forms, for, even if we are not athletes, nearly one-half of our body is made up of muscle which is one-fifth proteid, and the nitrogen in this proteid can only be furnished by proteid again, since neither fats nor carbohydrates contain any of it; therefore in making up bills of fare, let us remember that growing and working proteid, yes, even idle proteid as Dr. Smith found, needs proteid, and that there is nothing in any of the other food principles that can entirely take its place.

Though we think of proteid mostly as a great body builder and restorer, it can also to some extent furnish fat when it stands in a certain relation to the fats and carbohydrates of our food, and we are assured by experimenters that it also furnishes heat and muscle energy under certain conditions.

In these last two activities, however, it is far excelled by fats and carbohydrates. We shall therefore think of it as the nitrogen

furnisher of our tissues, and also as the grand stimulant among foods, inciting the body, as it does, to burn up more of other kinds.

Scientists, at one time, held the opinion that our muscle energy comes chiefly from proteids. This view has been abandoned, but many a working man still believes that meat is the only kind of food that is of any account; he thinks of fats and starches as quite unimportant comparatively. Now it has been proved over and over again, that we can combine meat with fats and vegetable food in such a proportion that it shall play only its main rôle, viz, that of building and restoring, while these latter furnish the heat and muscle energy needed. Proteid food is such a costly article that it will not do to put it at work which cheaper material can do even better.

FUNCTIONS OF FATS.

The fats also have more than one office in the body. They can be stored as body fat, or they can be burned and give off heat, and they may also serve as a source of muscular energy, in an indirect manner at least

FUNCTIONS OF CARBOHYDRATES.

The carbohydrate principle furnishes fat to our tissues, and is a source of heat and muscle energy, indeed the chief source of muscle energy in all ordinary diets.

FLAVORINGS.

So far we have had chiefly in mind the real working constituents of food, if we may so speak. But many things cannot be studied or classified in the above way; they must be looked at from another point of view.

Thus a pinch of pepper, a cup of coffee, a fine, juicy strawberry, what of these? They may contain all five of the food principles, but who cares for the proteid action or corbohydrate effect of his cup of good coffee at breakfast, or what interest for us has the heating effect of the volatile oil to which the strawberry owes a part of its delicious taste?

Surely the economical housekeeper who would throw out of the list of necessaries all the things that tickle the palate, that rouse the sense of smell, that please the eye and stimulate our tired nerves, just because these things contain but little food, would make a grave mistake. She may know just what cuts of meat to buy, what