Animal Foods.-The figures for meat, game, fowl, milk, eggs, etc., as well as those for vegetable food, are from European analyses, which are far more numerous at present than the American. Those of fish and invertebrates, on the other hand, are American-the number of analyses made here being already several times as large as the European. The first column of the table of animal foods gives the amounts of edible solids, actual nutrients in the samples as analyzed. The European figures do not include these data. With the fish and invertebrates, however, they are given. TOTAL EDIBLE SOLIDS. ACTUAL NUTRIENTS IN SAM- KIND OF FISH, AND PORTION ANALYZED. Salmon, entrails removed. Smoked halibut.. Salt inackerel.. Canned salmon Smoked herring Halibut, section of body, fat. Salt cod, boat fish". Considered from the stand-point of the foodvalue, meats, fish, etc., as we buy them in the markets, consist of-1. Flesh or edible portion; 2. Waste-bones, skin, entrails, etc. The proportions of waste matter in different kinds of fish, and in different samples of the same kind in different condition, vary widely. Thus, a sample of flounder contained 68 per cent of Mackerel, whole. waste matter and only 32 per cent of flesh, while one of halibut-steak had only 18 per cent of waste and 82 per cent of edible materials. Among those with the most waste and least edible flesh are the porgy, bass, perch, lobster, and oyster. Among those with the least waste are fat shad, fat mackerel, and dried and salt fish. Coming to the edible portion, the flesh, we find this to consist of-1, water; 2, solids— actual nutritive substances. The proportions of water and solids in the various kinds of flesh are much more variable than most people would suppose. Thus, we find the proportion of water in meats to vary from one half or less in the fatter to three fourths or more in the leaner sorts. Again, the flesh of flounder has 85 per cent of water and only 15 per cent of solids, while that of salmon has 365 per cent of solids and 633 per cent of water; and the flesh of dried, smoked, and salt fish has still less water. Among the more watery kinds of fish are the flounder, cod, striped bass, and blue-fish. Among those with less water and more solids are mackerel, shad, salmon, and salt and dried fish. In brief, as compared with ordinary meats, the flesh of fish generally, though not always, contains more water. To get the actual nutritive substance in a sample of fish we must first subtract the waste -the entrails, bones, skin, etc.-which leaves the flesh; then we must allow for the water in the flesh. What remains will be the total edible solids, or actual nutritive substance, in the sample. Some of the detailed statistics of the proportions of total nutrients in fish and invertebrates will be of interest. The following data are from a report of the investigation by Professor Atwater above referred to, in the last report of the United States Commissioner of Fish and Fisheries. The figures apply to the samples of fish as retailed, in some cases whole, in others dressed: VOL. XXI.-43 A Mackerel, whole. California salmon, edible portion of anterior Per cent. Per ct. 89-39 26.57 81.63 30.97 30.91 29.95 25.66 Eels, salt-water; skin, head, and entrails re- Salinon-trout, whole, lean. 14.88 13.69 Spent salmon, female, whole. Sheep's-head, entrails removed. Herring, whole. Cod, head and entrails removed. Red snapper, entrails removed.. White perch, whole. White perch, whole.. Black bass, whole Striped bass, whole.. Foul or Spent Fish versus the same in Good Condition.-Some very interesting results are found in comparing the foul or spent fish with the same in good condition. As it becomes lean, the fish loses nutritive value in three ways: first, in total loss of weight; second, in relative increase of waste and decrease of flesh; and, third, in the deterioration of the quality of the flesh, which, in the lean fish, is more watery and considerably less valuable, pound for pound, than the flesh of the same fish in good condition. Thus, the flesh of spent salmon is rated in the last column at 85, while that of fat salmon came up to 108. There is in this a strong argument in favor of legislation against the capture of fish out of season. Fish as Brain-Food.-The report referred to contains the following statement regarding the wide-spread notion that fish is particularly valuable for brain-food on account of a large con that account, be better for brain-food. The questions of the nourishment of the brain and the sources of intellectual energy are too indeterminate to allow decisive statements, and too abstruse for speedy solution in the present condition of our knowledge." tent of phosphorus: "The percentages of phosphorus in the analyses above reported are not larger than are found, according to the best analyses, in the flesh of other animals used for food. The number of reliable determinations of flesh in the latter are, however, small, and it is, though very improbable, yet within the range of possibility that a more complete investigation of the subject might reveal a smaller proportion of phosphorus in meats than in fish. But, even if the fish were richer in phosphorus, there is no proof that it would, on PROPORTIONS OF FLESH, OF LIQUIDS, AND OF TOTAL SHELL CONTENTS (FLESH AND LIQUIDS) IN SAMPLES OF OYSTERS. Oysters. From the same source we quote similar statistics regarding oysters from various localities. It should be observed, however, that the analyses are as yet insufficient to show how accurately these figures express the average composition of oysters of the kinds named: Norfolk.. The actual nutrients in the samples of oysters were as follows: Placing the oysters in the order of the percentages of nutritive materials in the whole sample, the arrangement will be as follows. Some other invertebrates are appended for comparison: PERCENTAGES OF NUTRITIVE MATERIALS IN WHOLE Rockaway. Stony Creek.. Per cent. 2.69 2.53 2.53 2.38 Fair Haven. Buzzard's Bay 2.25 1.87 Stony Creek. 1.76 1.68 Proportions of Nutritive Ingredients.-Columns two to six of the table of animal foods, on page 672, show the proportions of water and of actual nutrients-protein, carbohydrates, fats, and mineral matters-in the several materials, and need no further explanation. We may, however, note three important facts which the figures illustrate: First, that, in general, the fatter kinds of flesh have more solid dry substance and less water than the leaner; second, that the flesh of fish is, in general, more watery than that of domestic animals; and, third, that otherwise the fish and meats are very similar in composition. The seventh column shows the nutritive ratios-that is, the ratio of the nitrogenous constituents (protein) to the non-nitrogenous ones (carbohydrates and fats)-a matter of importance in judging of the fitness of a given food or food-mixture for supplying the wants of the body. A nutritive ratio of 1 to 5 is usually re garded as a fair one for this purpose. The familiar fact that neither lean meat nor a very starchy food, as potatoes, is by itself proper for food, but that each supplements the other and the two make an appropriate mixture, is an illustration of this principle. The nutritive ratio of the meat is too small-protein is in excess; that of the potato is too large-protein is deficient. The two together in proper proportions give the proper nutritive ratio. Vegetable Foods.-The vegetable foods are in general more concentrated-that is, they have less waste, less water, and more dry substance, actual nutrient-than the animal foods. On the other hand, the dry substance is less valuable, weight for weight, than that of animal food, partly because it has less protein and consists largely of carbohydrates, and partly for other reasons, as is explained beyond. Nutritive Valuations.-From the figures in the table it seems that, while "medium beef" contains 72 per cent of water, milk contains 87 per cent. Roughly speaking, beefsteak is about three fourths and milk seven eighths water. A pound of beefsteak would thus contain four ounces of solids, and, if we assume a pint of milk to weigh a pound, a quart would contain four ounces of solids also; that is, a pound of steak and a quart of milk contain about the same weight of actual nutrients. But we know that for ordinary use the pound of beefsteak is worth more for food than the quart of milk. The reason is simple. The solids of the lean steak are nearly all albuminoid, while those of milk consist largely of fats and of milk-sugar, a carbohydrate. The figures in the last column are intended to show how the foods compare in nutritive value, "medium beef" being taken as the standard. They are computed as ascribing certain values to the albuminoids and fats, and taking the sum in each case for the value of that particular food. The ratio here adopted, which assumes one pound of albuminoids to be equal to three pounds of fats and five of carbohydrates, is now a current one in Germany. These estimates for animal foods are based upon German market prices, beef and pork being taken as standards. The estimates for vegetable foods are in like manner based upon the composition and costs of rye-flour and potatoes. The details of the method, by which these estimates are reached would hardly be in place here. Suffice it to say that the valuations are found to accord fairly well with the actual relative costs of the nutrients in the plain, substantial foods, whose prices seem to be regulated, not by their flavor nor by the influence of the selective tastes of the wealthy, but by their actual efficacy for supplying the wants of the people the efficacy which is tested by average experience, and formulated, in so far as it is formulated at all, by the relative prices which are paid by those classes of the community who can not afford luxuries, but must buy what Thus it seems that, in the German markets, the same nutrients cost not far from five times as much in animal as in vegetable foods. Probably the ratio would be about the same in our own markets. While these data accord with general experience in showing that vegetable foods are much cheaper than animal, it is hardly right to infer that, for actual use, the disparity is as great as above indicated. A discussion of this question would be out of place here. It is worth noting, however, that, in general, the animal foods are the more digestible, that most men crave them, that even the poor will pay for them, and that, as is shown by the general use and the efficacy of meat broths and meat extracts, there seems to be something in the peculiar constituents of meats which supplies a want that vegetable foods do not wholly meet. It should be especially observed that the valuations of animal foods in the table are as referred to "medium beef," while those of vegetable foods are as compared with fine wheat-flour. General Considerations affecting the Nutritive Values.-Three things should be said with reference to the table: 1. The figures represent general averages. Sometimes different samples of the same kind of flesh will show widely varying percentages of constituents. This is particularly true of the fats, and to a less degree of the water. Vegetable foods are of more constant composition than animal foods. 2. The figures for some of the kinds of food are based upon few analyses. More are needed to show the actual range of variation and the averages. 3. The nutritive valuations are of necessity crude, and to be relied upon rather as approximations than as accurate quantitative statements. Much more chemical and physiological investigation is needed to make our knowledge of these as complete and satisfactory as it should be. Of these considerations, perhaps the digestibility of the different foods is as important as any. Digestibility of Foods.-The question of the digestibility of foods is very complex and difficult of solution. The data at present at hand are at best meager and ill defined. This is especially true as regards the ease or difficulty of digestion of different foods. The actual amounts digested and assimilated are capable of more nearly accurate determination. Indeed, the percentage of the more important constituents of various foods actually digested by domestic animals of different species, breeds, sexes, and ages, and under varying circumstances, has been a matter of active experimental investigation in the German agricultural-experiment stations during the past twenty years. Briefly expressed, the method consists in weighing and analyzing both the food consumed and the solid excrement, which latter represents the amount of food undigested, the difference being the amount digested. Between one and two thousand such series of experiments have already been reported. The data thus accumulated enable us to construct tabular statements of the digestibility of a great variety of feeding-stuffs by ordinary animals, as horses, oxen, cows, sheep, and swine. A considerable number of experiments have, however, been carried out, notwithstanding these difficulties, and have given us definite results of no little interest. In an article in the "American Agriculturist," on the "Amounts lost from Various Foods through Non-Assimilation," Professor Storer, of the School of Agriculture of Harvard University, has given the preceding table, based principally upon results of a very elaborate research by Rubner, of Munich. This subject is so important, and withal so new to those who do not follow closely the results of the latest foreign research, that we quote further from the article referred to: It is to be observed that the figures of the second column of the table give no more than an approximate idea of the value of each of the foods enumerated. A more precise conception of these values may be had by comparing the figures of column two with those in Such experiments upon human subjects, the third and fourth columns, which give the percenthowever, are rendered much more difficult by age amounts of nitrogen and of carbohydrates that the necessity of avoiding complex mixtures of have escaped assimilation. It is noteworthy that the foods, in order that the digestibility of each chemical composition of dung is often very unlike that of the food from which it has been derived. It particular food or food ingredient may be dedoes not at all follow, for example, that the dung will termined with certainty, and the fact that it be highly nitrogenized when food has been eaten is not easy to continue to eat the same kind of which is particularly rich in nitrogenous constituents, food long enough for a satisfactory experiment. for it may happen in this case that a large portion of No matter how palatable a simple food may be the nitrogen is voided in the urine. Rubner found, for instance, 64 per cent of nitrogen in dry excrement to a man at first, it has been found that it will from a meat diet, though the flesh had contained 14 per almost certainly become repugnant to him cent of nitrogen; in dry excrement from milk he after four or five days. In consequence, the found but little more than 4 per cent of nitrogen; digestive functions are disturbed, and the acwhile he found as much as 8 per cent of nitrogen in curacy of the trial is impaired. In the experi- with meat and milk, is a substance to be regarded as the excrement from white bread, which, as compared ments now in question, it was quite exceptional poor in nitrogen. On referring to column four of the to find persons, in any walk of life, who could table, it will be seen that much larger amounts of continue to eat large quantities of simple, plain nitrogen went to waste in the case of vegetables which food for tolerably long periods-a fact, by-the-so-called animal foods, such as flesh, eggs, and milk, were themselves poor in nitrogen than in that of the way, which strikingly illustrates and empha- which contain a large proportion of this element. In sizes the importance of a varied diet in ordi- deed, it is probable that the nitrogen in the animal nary life. foods is really assimilated well-nigh completely, and that the larger part of what little nitrogen is actually found in the dung from such foods is actually part and parcel of certain biliary products, secreted from the body, which have done duty in the process of digestion. In this view of the matter, such excremental nitrogen can not properly be classed with that wasted from the food through non-assimilation. Some of this biliary nitrogen occurs, of course, in all excrement, about as much in one kind as in another, and a mental reservation must always be made on account of it. KIND OF FOOD EATEN. Mixed diet. Percentage PERCENTAGES OF THE Nitrogen Carbohydrates Of the foods which go to ? Flesh... 5 or 6 2 or 3 ? 6 2 to 6 7 bread 7 8 to 24 12 to 14 9 81 to 51 19 to 26 1 to 15 32 11 15 1: 21 * Protein. 13 Several curious points of detail have been noticed in these researches. It appears, for example, that hardboiled eggs are assimilated by healthy men just as completely as roast beef is; though it may none the less be true that the flesh is digested and assimilated in less time than the egg, and that the organs of digestion are put to less trouble in dealing with it. It has been shown also, by several different observers, that bread alone is an insufficient food. On a breaddiet the body gives out each day more nitrogen than is assimilated from the food, and the coarser the bread so much the worse for the consumer. It appears from the table that milk is not so completely assimilated by adults as would have been supposed at first sight. Milk is distinctly inferior to beef and eggs in this respect, and is even worse than some of the foods of vegetable origin. The reason of this peculiarity appears to depend in good part upon the large amount of ash-ingredients that are contained in milk, and which are not assimilated by the body. This remark applies particularly to lime, which is abundant in milk, and which passes out from the body in the solid rather than in the liquid excrement. On leaving the ash-ingredients wholly out of the account, it appeared that the dry organic matter of milk was assimilated almost as well as that of flesh and eggs; though the percentage waste of nitrogen from milk is noticeably large-perhaps because of the large amount of this element which is taken into the digestive tract when nothing but milk is eaten. There is, of course, a limit to the digestibility of every food, milk included. Speaking in general terms, however, it is simply the ash-ingredients in milk that are not needed by adults which are discarded. In harmony with this fact, it has been noticed that milk is assimilated more completely by children than by adults. car Beef, medium.. Butter... 100 ! Mackerel... Cheese, skimmed milk 159 3 90.9 90-7 116 89.4 146 Striped bass... 80.4 151 Haddock. 74.9 Flounder 62.4 Oysters, Blue Point.. 44.3 163 0 849.0 "canned". 39.2 The completeness of the assimilation of the " bohydrates"-that is to say, starch, from foods rich in this constituent-is specially remarkable. It appears that men are able to digest and absorb very large quantities of starch when it is presented to them in suitable forms, as in rice, white bread, and macaroni; unless, indeed, a great deal of fat is caten at the same time with the starch, in which event some of the latter is apt to escape digestion. In the case of potatoes, black bread, beets, and cabbage, on the other hand, the carbohydrates are utilized much less completely; Salt cod.. doubtless because they are of less digestible kinds in the vegetables, and also because each of the foods last mentioned produces large quantities of bulky, watery excrement which passes rapidly through the intestines, and carries with it much carbohydrate and other material, which would doubtless have been assimilated but for lack of time. Not only are the intestines overburdened by these coarse foods, but the partially digested material is subject to fermentations which produce butyric and lactic acids, and a quantity of gases, all of which appear to hasten the evacuation of the intestines, and consequently occasion less complete assimilation of the constituents of the food than would otherwise occur. Any solid, non-digestible substance added to food, such as bran, for example, or cellulose prepared from straw, makes the assimilation of the digestible constituents of the food less complete than it would be if the indigestible substance were absent. Of a given amount of starch, that would be completely assimilated if eaten in the shape of rice, white bread, or macaroni, no inconsiderable portion goes to waste if it be eaten in the form of black bread. In experiments where the diet consisted of beets alone, which were eaten, of course, in large quantities, the intestines were so overloaded that excrement began to be dis charged five or six hours after the first meal was eaten. Rice is assimilated pretty well, particularly as regards its starch (carbohydrates). Indeed, in so far as dry substance goes, rice is assimilated as completely as flesh; it is the nitrogenous constituents chiefly which fail to be absorbed. So too with Indian corn; a good deal of its nitrogen is not assimilated, while its carbohydrates are pretty thoroughly absorbed. With potatoes, also, a very considerable part of the nitrogenous constituents are not assimilated, and the amount of excrement is large. Particularly large amounts of excrement were produced when the food consisted of beets or of cabbage. As the table shows, very considerable portions of these foods were not assimilated. As a general rule, fat is assimilated wellnigh completely, even when eaten in large quantities, though exceptions to this rule occur, and are not always easy to explain. The fat of Indian corn, for example, and that eaten with cabbage, appear to be less easily assimilated than some others. Butter is assimilated better than fat bacon, and the appearance of particles of unchanged bacon in the excrement would seem to show that the cellular envelopes of such fat Canned salmon.. 98.2 It appears, from comparison of the German analyses of meats with those thus far made of the corresponding American products, that what is given above as "medium beef" would be regarded here as rather lean. Since, however, the valuations are only relative, this is of no great moment. These figures differ widely from the market values. But we pay for our foods in proportion, not simply to their value for nourishing our bodies, but to their abundance and their agreeableness to our palates. It makes very little difference to a man with $5,000 a year whether he pays 25 cents or $5 a pound for the albuminoids of his food, but it does make a difference to the housewife whose family must live on $500 a year. And a little definite knowledge of this sort will be of material help to her in furnishing her table economically. The cook-books and newspapers have occasionally something to say upon these points, but their statements are apt to be as vague and far from the truth as, in the lack of authoritative information, they might be expected to be. As already stated, the nutritive valuations above given are only approximate, since they are made with very imperfect knowledge of either the digestibility of the foods or the influence of palatability and other factors upon their nutritive value, and also because they are based upon very few analyses. But it is certain that we need to know more about these things, and that proper investigations will help us toward that knowledge. |