THE CHEMISTRY OF FOODS AND NUTRITION. I.* THE COMPOSITION OF OUR BODIES AND OUR FOOD. "Half the struggle of life is a struggle for food."- EDWARD ATKINSON. "I have come to the conclusion that more than half the disease which embitters the middle and latter part of life is due to avoidable errors in diet . . . and that more mischief in the form of actual disease, of impaired vigor, and of shortened life, accrues to civilized man. . . in England and throughout central Europe from erroneous habits of eating than from the habitual use of alcoholic drink, considerable as I know that evil to be."- SIR HENRY THOMPSON. "If we will care for men's souls most effectively, we must care for their bodies also."- BISHOP R. S. FOSTER. HAT proportion of the cost of living might be saved by better economy of food; how dietary errors compare in harmfulness with the use of alcohol; whether, as some urge, our next great reform is to be in our dietetics; and to what extent the spread of the gospel and the perfection of its fruit are dependent upon the food-supply, are questions which it is not my present purpose to discuss. I have quoted the foregoing statements, however, because they come with authority, and because, starting from the widely different standpoints of the economist, the physician, and the divine, the conclusions tally perfectly with those of some studies of my own. only in proportion as adequate nourishment of their bodies is provided for. I have been led to the conclusions that, in this country, many people, not only the wellto-do, but those in moderate circumstances also, use a needless quantity of food; that part of this excess, however, is simply thrown away, so that the injury to health, great as it may be, is doubtless much less than if all were eaten; that one great fault with our dietaries is an excess of meats and of sweetmeats; that even among those who desire to economize there is great pecuniary loss from the selection of materials in which the actual nutrients are really, though not apparently, dearer than need be; that many whose means are limited make still more serious mistakes in their choice of food, so that they are often inadequately nourished when they might be well fed at less cost; and, what seems the most painful thing of all, that it is generally the very poor who practice the worst economy in the purchase as well as in the use of their food. Mr. Atkinson cites statistics to show that all but the very few who are especially well-to-do, in this country as in Europe, must expend half or more than half of their earnings for their food; calls attention to our wastefulness, and urges the need of better economy in the purchase and use of food-materials. The error which Sir Henry Thompson most seriously deplores is over-eating. "It is a failure to understand, first, the importance of preserving a near equality between the supply of nutriment to the body and the expenditure produced by the activity of the latter; and, secondly, ignorance of the method of attaining this object in practice, which gives rise to the various forms of disease calculated to embitter and shorten life." Bishop Foster, considering, on the one hand, the destitution that prevails, both at home, and especially in some of the countries where missionary effort is put forth so vigorously, and, on the other, the intimate dependence of man's intellectual and spiritual development upon his physical condition, urges that we may hope for the best culture of the Christian graces in the hearts of men *See "The Food Question in America and Europe " by Edward Atkinson in this magazine for December, 1886. The subject concerns the laboring classes in still other ways. Statistics as well as common observation bear emphatic testimony to the better condition of the American as compared with the European workingman in respect to his supply of the necessaries and comforts of life. Nowhere is this superiority more striking than in the quality and quantity of his food. And the difference in the dietaries of the two is especially marked in the larger amount of potential energy, of capability to yield muscular strength for work and to fulfill other uses in nutrition, which characterizes the food of the American. That the American workman, in many cases at least, turns out more work per day or per year than his European competitor is a familiar fact. That this superiority is due to more nutritious food as well as to greater intelligence is hardly to be questioned. But the better nourishment of the American wage-worker, as we shall see, is largely due to our virgin soil. With the growth of population and the increasing closeness of home and international competition, his own diet cannot be kept up to its present nutritive standard, nor can that of his poorer neighbor and his foreign brother be brought up nearer to that standard, without better knowledge and application of the laws of food economy. Some time since, at the instance of the United States National Museum, and in behalf of its food collection, I was led to undertake a study of the chemistry of foods. This has included with other matter a series of analyses of some of our common food-materials. To give some of the more practical results of this work, especially as viewed in the light of late research upon the more general subject of nutrition, is the purpose of the present articles.* A POUND of very lean beef and a quart of milk both contain about the same quantity of actually nutritious materials. But the pound of beef costs more than the quart of milk, and its nutrients are not only different in number and kind, but are, for ordinary use, more valuable than those of the milk. We have here an illustration of a principle, or rather of two principles, of fundamental importance in the economy of nutrition: our food-materials contain nutrients of different kinds and in different proportions, and the nutrients have different functions, different sorts of work to do in the support of our bodies. Add that it is essential for our health that our food shall supply the nutrients in the kinds and proportions our bodies require, and that it is likewise important for our purses that the nutrients be obtained at the minimum cost, and we have the fundamental tenets of our system of foodeconomy. The greater part of our definite knowledge of these matters comes from chemical study of food-materials, and from experiments in which animals are supplied with food of various kinds and the effects noted. In these latter, the food, the egesta, solid and liquid, and, in many cases, the inhaled and exhaled air are measured, weighed, and analyzed. Hundreds, indeed thousands, of trials have been made with animals of many kinds, and a great number with human beings of both sexes and different ages. The best work has been done during the last two decades, nearly all of it in Europe, and the larger share in Germany. It involves the study of the profoundest problems of chemis * I am indebted to Professor Baird, Secretary of the Smithsonian Institution and Director of the National Museum, for permission to reproduce here several charts prepared to illustrate the food collection; nor can I forbear adding that it was through the generosity try, physics, and physiology, the most elaborate apparatus, and the greatest care and patience of the workers. The labor of days and weeks is often required for a single experiment of a series, and the result of many series may often be condensed in a very few words. If one seeks famous names in this field he may find them in Liebig, Pettenkofer, and Voit in Germany; Payen and Claude Bernard in France; Moleschott in Italy; and Frankland, Playfair, Lawes, and Gilbert in England, and many others. If he questions the practical value of the results, let him see how they are being applied in the construction of dietaries for the common people in Germany, and what they indicate as to the errors of our food-economy at home. If he would see how results of recent research in one country may be ignored, because unknown, by the writers. of a different language in another, let him examine some of our latest magazine articles and text-books, the names of the authors and publishers of which ought to be a guarantee for better things. What we wish to consider now, however, is not the extent of the science, but some of its more important teachings in their applications to our daily life. Our task is to learn how our food builds up our bodies, repairs their wastes, yields heat and energy, and how we may select and use our food-materials to the best advantage of health and purse. I begin our study together with a wholesome fear of the editor before my eyes, knowing well that back of the courteous hint to make these articles not too abstrusely scientific there was a repressed warning to avoid the tone and language of the college lectureroom as unsuited to the pages of a magazine. But I must crave a little latitude; the results of scientific research cannot be explained without some tedious technicalities and dry details. HOW CHEMICAL ANALYSES ARE MADE. IF I cannot be interesting, I will be orthodox, and go back to the Catechism, whose second question is "Of what are you made?” and the answer, "The dust of the earth." The fact that underlies this answer, namely, the identity of the elements of our bodies with those of the material objects around us, is one of the many which chemistry explains. This fact, embodied in the solemn language of the primeval curse, "for dust thou art, and unto dust shalt thou return," impressed upon us of Messrs. Thurber, Whyland and Co., of New York, in defraying a considerable portion of the pecuniary expense of the analyses hereafter referred to that the latter were made possible. with our earliest religious teachings, clothed in fantastic imagery by poets, and understood so vaguely in the science, and dwelt upon so mysteriously in the philosophy of the past, is divested of much of its mystery by the matter-of-fact investigation of the present. The chemistry of to-day tells us of what elements and compounds our bodies consist. It gives us at least a glimpse of the ways in which they are framed together by the wonderful processes of life, and how they go through the round of growth and fruition, and are by decay resolved again into the forms from which they came. And the research of the past few years has shown us that even this decay is a vital process carried out by living creatures, whose mission is to take off the effete matter and fit it for use again. A friend of mine tells of an editor of a prominent journal- and a Boston editor at thatwho was much surprised to learn that it is possible to tell by use of the balance, the combustion furnace, the filter, and other appliances of the chemical laboratory, just what elements and compounds and what proportions of each make up the air or a mineral, or how much nitrogen there is in muscle or protein in wheat flour. But to the chemist these are the most commonplace, though not always the simplest, things. Indeed, our every day handling of food materials often involves processes, though crude ones, of analysis. We let milk stand; the globules of fat rise in cream, still mingled, however, with water, protein, carbohydrates, and mineral salts. To separate the other ingredients from the fat, the cream is churned. The more perfect this separation, i. e., the more accurate the analysis, the more wholesome will be the butter. Put a little rennet into the skimmed milk, and the casein, called in chemical language an albuminoid or protein compound, will be curdled and may be freed from the bulk of the water, sugar, and other ingredients by the cheese-press. To separate milk-sugar, a carbohydrate, from the whey is a simple matter. One may see it done by Swiss shepherds in their rude Alpine huts. But farmers find it more profitable to VOL. XXXIV.-9. put it in the pig-pen, the occupants of which are endowed with the happy faculty of transforming sugar, starch, and other carbohydrates of their food into the fat of pork. The New England boy who on cold winter mornings goes to the barn to feed the cattle, and solaces himself by taking grain from the wheat bin and chewing it into what he calls "wheat-gum," makes, unknowingly, a rough sort of analysis of the wheat. With the crushing of the grain and the action of saliva in his mouth, the starch, sugar, and other carbohydrates are separated. Some of the fat, i. e., oil, is also removed, and finds its way with the carbohydrates into the stomach. The tenacious gluten, which contains the albuminoids or protein and constitutes what he calls the gum, is left. When, in the natural order of events, the cows are cared for and the gum is swallowed, its albuminoids enter upon a round of transformation in the boy's body, in the course of which they are changed to other forms of protein, such as albumen of blood or myosin of muscle; or are converted into fat, or are consumed with the oil and sugar and starch to yield heat to keep his body warm and give him muscular strength for his work or play. I am using such technical terms as protein and carbohydrates and speaking of chemical processes with which daily usage makes us chemists familiar and which the reader will find referred to so often in these articles that I wish him to become familiar with them also. Indeed, these things are so much a part of ourselves, so intimately connected with our every breath and motion and feeling, with our life and health and strength, that labor spent in learning about them cannot be lost. It will help toward understanding the facts if we note how some of them are found out. To this end I will introduce the reader into a laboratory, being aided in so doing by the illustrations of the chemical laboratory of Wesleyan Univer MAKING OXYGEN. sity. They show the rooms in which some of the studies whose results are to be described beyond were made, and part of the apparatus actually employed. At one of the desks a student may be seen preparing oxygen. In a little flask he places some chlorate of potash-the material which we use as a medicine for sore throat. This he heats by the flame of a peculiar lamp underneath the flask. The oxygen is given off as gas and passes through a glass tube which is bent downward so as to open under the mouth of a glass jar, which latter has been filled with water and inverted over water in a basin. The oxygen bubbles up into the jar, while the water at the same time runs out, and thus the jar is filled with the gas. It looks like ordinary air, but when the experimenter sets fire to a stick of wood, blows out the flame, thrusts the glowing end in the oxygen, it bursts instantly into a brilliant flame. A piece of phosphorus, kindled and placed in the oxygen, burns with a flame of blinding brightness. And a steel wire burns in this gas even more brilliantly than wood burns in ordinary air. Thus the student learns as he could not from textbook or lectures, that oxygen, which makes up nearly two-thirds of the weight of our bodies, and one-fifth of the weight of air, is the great supporter of combustion. But our special purpose here is to note how chemical analyses are made. Let us take as an example a grain of wheat. It contains water, which we may dry out by heating; organic matter, which may be burned by combining with the oxygen of the air; and mineral mat driven out. When it is perfectly dry it is weighed again. The loss in weight represents the quantity of water in the flour. This heating is conducted in a drying oven which is kept hot by a gas flame inside the support on which the oven rests. In order to prevent the action of the oxygen of the air upon the flour while it is being dried, we keep a current of hydrogen gas continually passing through it. The apparatus for generating the hydrogen and forcing it through the flasks is shown in the ters, which remain behind as ashes. The organic matter contains fatty or oily substances, starch and other carbohydrates, and protein compounds. The object of the analysis is to separate these ingredients from one another and find what proportion of each is contained in the wheat. To make the analysis, we first grind the grain to flour. To find the proportion of water, we weigh off a small quantity very accurately in a chemical balance and put it in a little glass flask, the weight of which is known, and heat it for a number of hours, until the water is picture. In the large bottles above is sulphuric acid. This runs down the pipes into the tall narrow glass vessels on the floor. These latter contain zinc. When the acid comes in contact with the zinc, hydrogen gas is developed, and passes up by tubes through the top of the drying oven into the flasks. Such devices as these are necessary if we are to make large numbers of analyses with the greatest accuracy and speed. Like a steam-engine, they seem a little complicated, but the engineer understands his engine, and to the chemist his apparatus seems perfectly simple. MAKING A NITROGEN COMBUSTION TO DETERMINE AMOUNT OF NITROGEN IN A GRAIN OF WHEAT. We have next to find out how much oily matter the wheat contains. For this purpose we must have some means of getting the oil out, and weighing it. The operation is by no means a difficult one. Suppose we have a mixture of sugar and sand and wish to find out how much sugar it contains. Sugar dissolves in water, sand does not. If we pour water into the cup containing the mixture, the sugar will dissolve, and if we pour off the water again the sugar will go with it and leave the sand behind. If instead of a cup we put the mixture in a little cloth sack, with meshes so fine that the sand will not pass through, and hold the sack over a dish and pour water into it, the water will dissolve the sugar and percolate through the cloth, carrying the sugar with it into the dish below. If then we boil off the water, the sugar will remain. We make use of an operation analogous to this in separating the fat from our wheat. The fatty and oily matters of the wheat dissolve in ether; the starch, gluten, and other ingredients do not. We therefore use ether in place of water for the solvent. Instead of the bag we place the flour in a little glass cylinder (I) having its lower end covered with filter paper. This small tube is put inside a larger one (O) whose lower end is drawn out into a neck like that of a funnel. This neck is then passed through the stopper of a little flask (F). If now we pour ether into the inner tube, it will dissolve the fat, percolate through the filter paper, and fall into the flask below. By passing successive portions of ether through the flour, we shall, after a time, dissolve out all the fat. But this would require a great deal of time and ether, both of which are expensive. Suppose we had some means by which the ether, after bringing its freight of fat into the flask, could be driven out, leaving the fat behind, caused to return into the inner tube, dissolve another portion of fat and bring it into the flask, and be made to repeat the round again and again. Suppose, furthermore, this operation should be made to go on automatically, and that it could be carried on in several of these pieces of apparatus at once, while the analyst devoted himself to other work. Our analyses would thus be greatly facilitated. Precisely this is done in the apparatus at the left of the drying oven in PAT EXTRACTION. the large picture, which shows the I F APPARATUS FOR than water, changes to vapor and passes upward between the inner and outer tubes into a long pipe which winds upward through the tank above like the worm of a still. The tank is kept filled with cold water; the ether vapor is condensed to liquid, falls back upon the flour in the inner tube, dissolves out another portion of fat, carries it into the flask below, and is then once more evaporated, leaving the fat in the flask; and so the same portion of ether keeps on its round, passing up in the form of vapor, coming back as liquid, and bringing fat with it into the flask. When the fat is all extracted the operator takes the apparatus apart, boils off the ether once more, and weighs the flask with the fat. Knowing how much the empty flask weighs, he has simply to subtract its weight from that of the flask with the fat in it; the difference is the weight of the fat. The ways of finding the amount of nitrogen in food materials are of especial interest to us, because we use the nitrogen as a measure of the amount of protein, the most important of the nutritive ingredients. One of the most common of these ways, the "soda-lime method," as it is called in the laboratory, is illustrated in pictures herewith. The flour is heated with a mixture of soda and lime in a combustion-tube. The small diagram shows the tube ready for the heating or "combustion," as it is termed. Connected with the long combustion-tube which holds the flour and |