But because nearly every kind of food contains other constituents besides the one which is chief, the housekeeper who wishes to make wise menus will need more and more detailed statements of food values as she is able to get and understand them. If she has hitherto thought little about such matters, she will probably not know that the United States Government has very kindly employed people to make years of experiments and to write books and pamphlets for her help, nor will she know that she may have these last merely by asking the Department of Agriculture for them. They are not made into attractive booklets, but they are by no means dull reading. Farmers' Bulletin No. 142, for instance, called "Principles of Nutrition and Nutritive Value of Food," and written by Dr. W. O. Atwater, is brief, helpful and most interesting. The figures in the table given below were taken from this Bulletin. But there are things which may be derived from this and the many other food pamphlets issued by the Government which are quite as important as definite statistics. They are things which give the housewife a feeling of comradeship with many people who are working earnestly with and for her; things which increase her interest in her own small part of the work and which give her a helpful sense of its dignity. For many reasons it is impossible for a housewife to make an _exact_ calculation of the amount of nourishment which she gives her family. The figures in even the most carefully made tables are, of necessity, averages or approximates, for food varies in quality in different localities and at different seasons. Moreover, the figures in the various government reports upon food values and in books giving such statistics differ somewhat, nevertheless, there is sufficient general agreement upon which to base an intelligent effort to make wise as well as agreeable menus. On this account, a housewife who is neither very learned nor very experienced can yet wisely regulate her menus by keeping in mind the general character of a day's nourishment and helping out her lack of chemical knowledge with a table of food values such as the one below. The general aim in providing food, as has already been said, is to furnish all the varieties of nourishment which the body requires and the chief ones in about the proportion of a fifth protein to a fifth fat to three-fifths carbohydrates. That is, either the per cent. of protein or the per cent. of fat multiplied by three should about equal the carbohydrates. This is, of course, a very rough and general way of estimating, but I believe it to be a practical way to begin the study and application of a branch of difficult and as yet slightly established knowledge.