Owing to the fact that the tissues of the normal body are constructed chiefly from proteids, the metabolism of proteids or nitrogenous foods is of very great importance. When we realize the fact that muscle, blood, brain, nerves, cartilage, tendons, the various internal organs and the tougher material of the skeleton are only various forms of proteid material, and must contain their proportions of available or organic nitrogen, we can understand why nitrogenous foods form a distinct class that must be considered by themselves. Only the mineral deposits of the bones and the teeth, and the globules of fat that are deposited as a source of stored energy represent the nitrogen-free class of substances within the animal body.

THE USE OF PROTEIDS IN THE BODY

The first use Nature makes of proteids in the body is in the actual adding to or increasing of body-tissue. When an emaciated young man from the city goes to work on a farm and gains twenty pounds, the cells of his muscles have actually increased in size and number. This requires proteids, which can be obtained only from the nitrogenous material in food. The growth during early life is due to an actual increase in the size of all the organs of the body, and is merely an accumulation of proteid substance.

The second use of proteids, and the one which, in matured life, is of more importance than those already referred to, is in the formation of the various nitrogenous products which are produced in connection with the different processes of the body and which are destroyed by the function of life. For example, the pepsin of the gastric juice is a nitrogenous substance which can be formed only from proteids. All digestive enzyms and other substances in the muscles, nerves, and in the various organs throughout the body are of a nitrogenous nature, and in their formation and use a certain amount of proteid material is consumed. When the digestive enzyms are formed from proteids, they consume more than their own weight of proteid material.

The third form in which proteids may be consumed in the body is in the actual replacement of worn-out cells. The skin, the hair, and the mucous or lining membranes of the body-cavities are constantly being cast off on the external surface, new cells being formed underneath. When cells within the interior of the body have become injured, or have passed their usefulness, they are removed by the phagocytes or white blood-corpuscles, and must be replaced by other cells. In the case of bacterial infections, as tumors, boils, or contagious dis-eases, the bacteria feed upon the proteids of the blood. The white blood corpuscles are destroyed in the conflict, or effort to remove the intruders, and all these substances must be replaced by proteids from food.

THE ACTION AND THE COMPOSITION OF PROTEIDS

The gain or loss of body-proteids is indicated by the gain or loss of nitrogen. The income of nitrogen can be ascertained by analyzing the food. The outgo of nitrogen is computed by analyzing the products excreted from the body. If the body at the beginning and at the end of an experimental period is carefully watched, and the income and the outgo of nitrogen determined, we can compute the amount of gain in the body that is nitrogenous tissue. The other gain or loss of body-weight must be fat. These calculations cannot be made exact, owing to the amount of food and water that may be in the digestive organs at the time the various weighings are made.

We have learned that in the digestive tract foods are converted into a soluble form of proteid known as peptone. The purpose of this conversion and the fine subdivisions of food produced by the various digestive juices are to reduce it to a form which will readily pass through the walls of the alimentary canal.

This is all that was known about proteid metabolism until within very recent years. The older scientists followed proteid digestion until the soluble peptone stage was reached, at which point all track was lost of the chemical changes and processes until the nitrogen was again excreted by the kidneys in the form of urea.

No scientist attempted to explain how the radically different proteids, such as egg-albumin, milk-casein, and wheat-glutin could appear in the body as blood-globulin, brain-lecithin, or as a myosis of the muscles.

The history of all these investigations cannot be fully explained here, but the discussion must be confined to that which actually takes place in the metabolism of proteids.

Proteids, as the student will remember, contain carbon, hydrogen, oxygen, and nitrogen, and sometimes small quantities of sulfur, phosphorus, or iron. These forms of proteids are now known to be chemically changed, by the digestive enzyms of the intestines, into simpler compounds containing these same elements.

These simple nitrogenous substances pass into the liver. Just as the liver regulates the supply of blood sugar, so it regulates the supply of nitrogenous compounds in the blood. A certain amount of proteid-forming material is passed through the liver, and goes on to perform the various functions for which proteid is utilized in the body. All nitrogenous material in excess of the amount required by the body is secreted by the liver, and the nitrogen, together with a portion of the carbon, hydrogen, and oxygen, is split off, forming urea, which is excreted by the kidneys. The remainder of the proteid substance, having been robbed of its nitrogen, is now essentially the same as carbohydrates, and goes to form glucose or blood-sugar, which may in turn form body-fats.

In the light of this explanation, we can understand several things already mentioned. It has been stated that proteid is the most essential food material of the body because it alone contains the nitrogenous compounds from which the body-tissues, and the chemical enzyms which control all living processes, can be constructed. But we now see that as important as is a supply of proteid materials, any excess above the body-needs is immediately turned into glucose and urea. The glucose, though useful to the body, could be taken in a simpler and less expensive form, while the urea is a waste-product, harmful to life, and must be immediately excreted by the kidneys.

The nitrogen that is actually used in the body serves a different purpose from that which is split off from the excessive proteid taken as food. The food proteid is simply split by the chemical addition of water, much the same as starch and other carbohydrates are changed into glucose. The proteid that is really used by the body is oxidized, and is excreted by the kidneys chiefly in the form of creatinin and uric acid.

FOOD STANDARDS

The term "dietary standard," as it has been applied in the past, means the quantity of the several nutrients that should be taken by the human body under its varying conditions. During the past twenty-five years, many investigations have been made in this country, Europe, and Japan, regarding the amount of foods consumed by various groups of people. All the facts gathered, which include more or less accurate records of the foods eaten by many thousands of individuals under all circumstances and conditions of life, are invaluable scientific data, but the interpretation that has been placed upon these interesting observations is one of the most conspicuous blunders made by the scientific world. Whether this criticism should fall wholly upon the men of science, who made these investigations, or upon the people who misinterpreted their meaning, is perhaps an open question; but the fact remains that from the general teachings in physiologies, and from popular bulletins published by the National Government, very incorrect ideas have been widely spread respecting the amount of food required to maintain life and health.

In order to give the reader some idea of the results obtained, when data is kept each twenty-four hours, of the amount of food consumed by various people on the conventional diets of civilization, I will select at random some of the results that have been recorded in these investigations, and will give in the Vieno System the approximate results. (See "Vieno System of Food Measurement," Vol. III, p. 639):

From such records Government standards have been roughly approximated. The standards published by the Government, computed by Prof. Atwater, and commonly known as the Atwater standards, are as follows, expressed in vienos:

The Atwater standard for women is estimated to be four-fifths of the amount of food required for a man under similar conditions.

It is generally recognized by investigators that these so-called standards are faulty, but by mutual agreement it seems that they have been accepted as the best that could be given. Faulty standards due to inexperience They lack accuracy because the men who prepared them lacked experience. Accuracy can come only from experience gained in the practical work; that is, in prescribing food, and combinations of food, for people under all the varying conditions of age, climate, and activity, and having these people report, at stated periods, the results of their dietetic prescriptions.

The average person eats what is set before him and asks no question about nitrogen and energy; nevertheless, advice so universally distributed as the Government Dietary Standards must exert much influence and have a considerable effect upon the habits of the people. Obviously the correctness of these standards is of vital importance to the health and the welfare of the nation.

A dietary standard should tell the quantity and the proportion of food required to keep the human body in its very best working state. The great error committed by the man who planned the above-named standards has been that he assumed that an average of what a man does eat is a criterion of what he should eat in order to maintain the best mental and physical condition. A greater error could not have been made. Our feeding instincts have been lost in the chaos of civilization. Both our appetite and our food have been perverted. We have been trained to want or to crave intoxicants, stimulants and sedatives; we have learned to relish things that have no food value, and we have grown to dislike the best food that nature produces, and to accept many of her worst. Dietary standards, therefore, made up from the conventional eating habits of the people, merely endorse their errors and pass them on to future generations. The work, therefore, of the true scientist is to point out these errors and to prescribe a remedy.

Man is a creature of habits, and civilized man is a creature of a great many bad habits. The argument that the average amount of food eaten is the amount that should be eaten falls under suspicion at once when we consider the fact that by a similar line of reasoning we could prove that the use of tobacco is necessary because the majority of men use it, or that slender waists are necessary to good social standing because a few million women so consider them.

The idea has been spread far and wide that the diet of the American working man, which is the richest in proteid of any race in the world, is responsible for the greater economic thrift of the American people. It is a matter of history that rich diet is always associated with prosperity, but the theory that the diet is the cause of the prosperity is an egregious error. Meat and rich foods gain a hold upon the appetite as do alcohol and narcotics. When nations or cities become wealthy, intemperance in eating is the usual result, but this in nowise indicates that a heavy consumption of food is the cause of a nation's greatness. History recites many instances of the rise and growth of a people to power and prosperity, together with the consequent adoption of excessive and luxurious habits of eating and drinking, only to be followed by physical deterioration.

It is not the quantity of food that is eaten, but the quantity of food that will give the greatest vitality and capacity to do things, that should determine our dietary standards. It is reasonable to assume that this amount would be the least quantity that would maintain activity without using up the food material stored in the body. All food taken in excess of the amount actually required must be cast from the body at a tremendous expense of energy. To do a given amount of work, or to add one pound of muscular tissue to the body, requires a definite quantity of energy-yielding or tissue-building material, but if more food is taken than the body can use, the excess ferments in the stomach and in the alimentary tract, producing poisonous products which are absorbed into the blood. These poisonous products cause a great number of human ills. The process of eliminating these poisons we call "dis-ease."

The assumption that the correct amount of food that should be taken by the body is the least quantity that will maintain normal body-functions, has been amply proved by recent scientific investigations to be correct. Many years of experience on the part of the writer have shown that to make food remedial and curative, the old dietary standards must be, roughly speaking, cut in half.

TRUE FOOD REQUIREMENTS

The degree of energy required by the body depends very largely upon the amount of work or activity it undergoes, hence the amount of food required to supply this activity cannot be accurately prescribed when the degree of required energy is unknown. However, there is a certain amount of work performed by the beating of the heart and in the maintenance of body-heat which can be fairly well estimated. The quantity of energy-yielding food required, each twenty-four hours, for the maintenance of the activities of life is about one vieno for every ten pounds of body-weight. For a man at steady muscular work, such as a carpenter or a farmer, this quantity should be about doubled. The quantity required by a man of sedentary habits, but who takes regular exercise for an hour or two each day, is about half way between these two amounts. Thus, a man weighing one hundred forty pounds would require one and one-half vienos for each ten pounds, or twenty-one vienos of food each day. These weights apply only to people of normal flesh, who desire neither to gain nor to lose.

The fact that either fat or carbohydrates can be used as a source of muscular energy may be taken advantage of in prescribing dietaries for persons whose digestive organs are so impaired that they cannot digest a normal quantity of either of these nutrients, but who could digest a small quantity of either. This does not mean, however, that the proportion of fat and of carbohydrates in the food can be disregarded. The digestive processes involved are radically different, hence a suitable proportion of carbohydrates and fats should always be maintained.

With a view to guiding in a general way those who wish to adopt a standard of diet for ordinary use, and who consult tables in which fats and carbohydrates are listed separately, I might state that the fat should form about one-eighth the total source of energy, or one-sixteenth the weight of all water-free (solid) food eaten.

Until forty years ago the idea was held by scientists, and is still a matter of popular belief, that nitrogenous foods are the sole source of all muscular energy. This is quite a natural assumption. Lean meat is muscle. If a man eats the muscle of another animal, by the primitive process of reasoning, he should acquire muscle. This belief among people who are not acquainted with physiological chemistry is almost universal, while the facts are, the man who eats the muscle of an ox for the purpose of adding strength to his own biceps is acting no more wisely than the college boy who takes calf's brain for breakfast the day before examination.

The fact that nitrogenous foods are not a source of muscular energy has been repeatedly proved by experiments on man and animals too numerous to relate here. The sugar and the fat in the blood are taken into the muscle-cells, and there unite with the oxygen brought from the lungs, producing energy. When the body is fed upon proteids lacking a sufficient quantity of other food elements, a portion of this proteid is converted into glucose or sugar, which maintains body-heat and energy. This is what happens in the case of carnivorous animals that have excretory organs especially adapted to the converting and the eliminating of useless or surplus products.

It has been proved that dogs are capable of living for an indefinite period of time upon a diet containing only a small proportion of proteid matter, while maintaining health and increasing in weight. Thus we see that even carnivorous animals require, for the maintenance of the body-functions, a comparatively small amount of nitrogenous material. Their strength and heat-forming elements can be secured from carbohydrates and fats, probably to their actual benefit. It is interesting to note, however, that dogs as a general rule cannot live and thrive on a vegetable diet; a certain amount of animal proteids seems indispensable. The same principle applies to other carnivorous animals. Even ducks and chickens need a small percentage of animal proteids in order to properly thrive and develop.

In order to maintain good health, every person requires a certain amount of nitrogen, the quantity being governed by activity, exposure, age, and temperature of environment. The growing youth needs nitrogen to supply material for the tissue growth of his body; an emaciated person who wishes to increase weight, a person recovering from illness, or a man who is constantly performing strenuous work, would all require a generous quantity of nitrogenous food.

The lowest possible nitrogen requirement for one of normal weight has been determined by various methods to be from 40 to 60 decigrams per day. This quantity, however, is the actual amount that is used in the body-processes, and should be increased according to activity or exposure to the open air.

From the results of numerous experiments under normal activity, the quantity of nitrogenous food estimated to maintain the best bodily condition is about three-fourths of a decigram for each pound of body-weight; less than Amount of nitrogen required by the body one-half of a decigram per pound of body-weight would cause nitrogen starvation, while more than one decigram per pound, except in the cases just mentioned, would result only in thrusting needless work upon the liver and the kidneys, whose duties are to guard the body against the results of incorrect eating. There are certain conditions under which this amount of nitrogen may be exceeded in order to gain definite and specific purposes, but in such cases the nature of the proteid is of great importance. In certain occupations, for instance sedative labor, the most soluble proteids, such as egg albumin (white of eggs), milk, and green peas and beans should be selected; while in cases of heavy manual labor, the heavier proteids, such as nuts, cheese, dried legumes, fish and fowl should be selected.

LESSON VII

FOODS OF ANIMAL ORIGIN

An intelligent discussion of this lesson leads us directly into a subject commonly known as "vegetarianism." The question whether man should eat the flesh of animals is especially fascinating for those who give attention to the food they eat. There are many standpoints, however, from which the subject of vegetarianism may be discussed.

In the first place, nearly all religious teachings that have wielded such a powerful influence over the civilization and destiny of men, have laid some restrictions upon the flesh-eating habit. Some religions require man to refrain from all animal products, while others interdict only the flesh of certain animals. Coupled with man's world-wide search for food, these religious teachings have played a conspicuous part in the question of human nutrition.

The second phase of the question that merits attention is the moral side, or vegetarianism from the animal's standpoint; in other words, the cruelty involved in the slaughter of our dumb friends and helpers, for whose presence here we are largely responsible. That the practises and customs which train humanity in cruelty toward animal life, are to be discouraged, cannot well be disputed, but this phase of vegetarianism is one which is somewhat without the realm of applied food chemistry, hence is mentioned only as a factor in the general discussion.

I will now consider vegetarianism from the standpoint of true food science, or the welfare of the physical man. It will be observed that in the lesson entitled "Evolution of Man," one of the first considerations taken up is the scientific Vegetarianism from standpoint of scientific living discussion of man's natural adaptation to the use of flesh foods. By natural adaptation I mean Nature's evolutionary plan of fitting the physiological organism to the food man is able to procure. The organism of man will, to a certain extent, adapt itself to a given diet within the brief period of one generation, just as, in the long ages of evolution, the digestive organs of any species of animal become adapted to such diet as may be procured. Thus it is of especial importance for us to know the diet of primitive man at a time before his intellectual resourcefulness made it possible for him to gather his bill of fare from the four corners of the earth.

The diet of our related anthropoid apes, of every primitive savage tribe, and of our ancestors, indications of which have been found in fossils and caves—all three throw light upon the subject. The consensus of these various studies indicates Primitive diet of man that the original or natural diet of man was one drawn chiefly from the vegetable kingdom, but not entirely so. Fruits, nuts, green vegetables, edible foliage, tubers or roots were all included in man's primitive diet. The foods of animal origin were varied, and consisted of such articles as birds, eggs, shell-fish, many insects, and other forms of lower animal life, of which our modern habit of eating frogs' legs, eels, escargots (snails), etc., is merely an inheritance.

Since the digestive, the assimilative, and the excretory organs of man have been constructed from, and adapted to, the use of vegetables, it is obvious that the flesh of animals is unnecessary, especially in view of the fact that there is nothing in flesh that cannot be secured from the vegetable world in its best and purest form. Man's primitive diet does not prove that he is by nature a vegetarian, as is the cow, and therefore entirely unsuited to digest any material of animal origin. The anatomy of man's teeth and of his digestive organs, however, indicates that he is by nature a vegetarian, and that his digestive organs are prepared to dissolve and to assimilate a diet that is somewhat more bulky than that of carnivorous animals, but, on the other hand, less bulky than the diet of animals which subsist wholly upon succulent plants, as do the purely herbivorous species.

Man is by nature a tropical animal, and so long as his habitat was confined to that section, he could live from the prodigality of Nature, but when he began his early migration northward, his food was the greatest problem he had to solve. He was often forced to choose between eating the flesh of animals and death from starvation. It was this fierce struggle for food, not the character of his food, which exercised both the physical and the mental powers, and caused the Aryan or northern races to think, and therefore to develop into people so much superior to their tropical brothers.

The defenders of flesh food often point to the fact that flesh-eating people have achieved the highest civilization. Man's superior achievement in northern countries can no more be credited to flesh-eating than to the wearing of fur caps or leather boots. To meet the exigencies of his environment, he was forced to think and to work, and thinking and working developed the brain and laid the foundation for his present stage of civilization.

Another reason for the early habit of flesh-eating is found in the fact that in order to sustain the required amount of body-heat in cold climates, a liberal consumption of fat was necessary. Vegetable fats not being available, his only source of supply was from the body-fat of animals.

Aside from fat, protein is the only nutritive element meat contains. With the variety of vegetable and butter-fats, and vegetable proteids available in this age, supplemented by our knowledge of chemistry as a guide in their use, the consumption of flesh as an article of human food is entirely unscientific and wholly without reason.

A diet composed exclusively of flesh contains fat and nitrogenous compounds only. These two classes of foods can, of course, maintain life, as was explained in our sixth lesson, as proteid is capable of forming blood, sugar, and body-fat. The fact, however, that the proteid or the fat of meat can be made to fill, in the physiological economy, the place naturally supplied by the carbohydrate materials of vegetable food, does not prove that such a diet is without its harmful effects. The living body has many wonderful provisions whereby life is maintained under unfavorable influences. Just as a blind person develops a sense of touch which in a way acts as a substitute for sight, so the ability of the body to convert either proteids or fats into sugar, may be utilized in cases of emergency, but the using of this emergency or substitute function of the body cannot develop and energize the human machine as well or as perfectly as can a naturally balanced diet. The fact that some people exist largely upon a meat diet does not prove that this is without its handicapping and evil influences, any more than the use of alcohol and tobacco proves that man is benefited by indulging in intoxicants and sedative poisons.

That flesh-eating is largely responsible for the universal desire among civilized people for some form of stimulant has ceased to be questioned by those who have been placed in a position to make experiments—the source from Flesh-eating produces appetite for stimulants which all real knowledge is obtained. These conclusions were first forced upon the writer by noticing the gradual decline of appetite for coffee and tobacco in his own case, when he began to subsist upon natural foods. With this hint no opportunity was lost, among the thousands of patients he treated, to observe the effects and get at the truth. If only one or two people had completely lost their appetite for all forms of stimulation, after following a natural food regimen, it might have revealed only an idiosyncrasy. When a dozen undergo the same treatment, with the same results, it leaves but little doubt that the theory may be true, but when many hundreds give the same testimony, through a period of a dozen years' practise, it reveals a truth that cannot be consistently doubted. Such experience proves beyond doubt that flesh-eating supports and perpetuates the habit of taking distilled and ardent liquors, tobacco, tea, and coffee, and the numerous drugs which, altogether, have done the human race more harm; dethroned more intelligence; sapped from the human economy more vitality; ruined more homes; made more widows and orphans; changed more natural virtue into vice, and caused more sorrow and tears, more failure and fears, than all other agencies of destruction combined.

Since fats and proteids are the only nutrients supplied by flesh foods, we may well ask, "Is meat the best source from which these elements may be secured?"

The proteid substance of meat includes all the edible portion of a carcass except the fat. The proteid of meat is more easily and more rapidly digested than the proteid of vegetables. Notwithstanding this fact, there are serious objections to the use of meat as a source of nitrogen. All flesh food contains the unexcreted waste matter of the slaughtered animal. When the process of metabolism that is continually going on during life is suddenly arrested by death, the effete and decomposing cells, and the partly oxidized waste-products which are still held in the muscle-tissues, are left in the flesh of the dead animal, hence these poisons must be consumed by the flesh-eater in order to secure the meat proteids and fats.

It is now a matter of common knowledge among scientists, and among the more advanced school of pathologists, that the usual conditions under which animals are slain change the chemical constituents of the blood-serum, charging it with a form of poison that to the chemist is as yet unknown, but the presence and the potency of which is attested by its effect.

The method of slaughtering animals in the great abattoirs is especially conducive to the generation of these poisons. The condemned herd is driven to the place of slaughter and killed, one at a time, in plain view of their fellows. These animals are very intelligent and possess remarkable senses of danger. They are as conscious of approaching death as the creature who takes their lives, hence the amount of poisons generated in their bodies is measured by the time they are kept in waiting. Most animals when killed labor under these conditions, and that these mental states render their flesh entirely unfit for human nutrition can no longer be questioned.

We find fragments of evidence supporting this theory in the fact that Nature's perfect food—the milk of a nursing animal, or of a nursing mother—can be changed in an instant into a poison by sudden fright, anger, or fear.

Thus we see that in eating meat, we are eating animal waste-material similar to that thrown off through our own body-cells. The waste material in meat being soluble, passes through the walls of our digestive organs, and enters the circulation, where it is added to similar poisons which are constantly being produced within our own bodies. It is the universal law of animal cell-growth that the waste matter of the cell acts as its own poison. When bacteria, growing in a solution of sugar, have excreted alcohol until it forms a certain percentage of the total contents, their activity ceases—they die from poisons thrown off from their own bodies. This is the reason that liquids containing a high percentage of alcohol must be distilled, and cannot be brewed. It is obvious, therefore, that in the consumption of flesh, we are adding to our bodies the poisons that are residual in the body of other animals, and are, therefore, approaching the conditions under which bacteria kill themselves by autointoxication or self-poisoning.

Plants utilize the carbon dioxid excreted by the animal, and the excrement of animals is in turn used to fertilize our fields. Although one form of life may utilize what is excreted by another form of life, the living thing that cannot get away from the excreted matter of its own activity is poisoned thereby.

The flesh of animals whose physiological processes are almost identical with our own, containing as it does waste-products that have not yet been excreted, must, when taken into the human body, add extra burdens to our excretory organs which are usually burdened with all they can do. Carnivorous animals are especially provided with an excretory system capable of taking care of such matter, but it is unreasonable to expect the excretory organs of man, which are not adapted to such a purpose, to throw off, in addition to the regular body-poisons, similar decomposing products of other animals.

It is true that flesh will support, and has supported what is commonly regarded as a high form of anthropoid life (man), but not having the natural standard from which to measure, we do not know how much better the opposite course would have been, or just how much longer one would live under a perfectly natural regimen. The effects of flesh-eating have not been definitely known until recent years, but is now acknowledged by the most advanced authorities to be one of the greatest errors of civilized people, and will, within a few years, disappear from the catalog of human habits, when the great masses of people are made familiar with the chemistry of food, and how to secure vegetable instead of animal proteids and fats.

MEAT

Meat, in the sense the word is here used, includes beef, mutton, pork, and an occasional allowance of wild game. Chemically considered, meat may be divided into two classes, namely (1) flesh or lean meat, and (2) animal fats. The former will be first considered.

1 FLESH OR LEAN MEAT

Lean meat is composed of the muscles of the animal. Approximately it is 70 per cent water, 20 per cent protein, and 10 per cent fat. The protein is composed of connective tissue, which is a tough, fibrous substance that forms tendons, and holds the muscle-cells in place. Chemically, connective tissue is formed of albuminoids, which were discussed in Lesson IV. These substances are somewhat difficult to digest, and are not of very great importance in the human body, as they cannot take the place of true proteid in tissue-formation.

The percentage of connective tissue in flesh depends upon the cut of the meat. As every housewife knows, the cheapest cuts of meat contain a larger amount of this material.

The gelatin of commerce is a manufactured product derived from the connective tissue of animals.

Other forms of protein are globulin and myosin, which form the actual muscle-substance. These elements form perhaps three-fourths of the entire proteid of the animal, and are the most valuable substances of flesh food. A very small portion of meat proteids is formed by the free albumins of the blood, which are mechanically retained in the muscle-cells, the purpose of which is the nourishment of the animal, and therefore are not unwholesome as food.

Another class of nitrogenous substances found in flesh foods is called meat extractives. Though they exist only in quantities of from one to two per cent of the weight of the flesh, they are the most interesting from the standpoint of chemistry, because they are found only in flesh foods, and are products only of cell life, hence not wholesome as food. They are composed of urea, uric acid, creatin, etc., and are similar or identical to the waste-products of human cell metabolism. The amount of these substances contained in flesh depends upon the condition of the animal at the time of slaughter, being much greater in animals slain after the chase, or laboring under fear or abuse.

The chemical composition of the different cuts of meat does not vary greatly, except in a greater or less per cent of fat, and no chemical calculation can compute this accurately, as the fat in every cut of meat varies widely.

Beef and mutton are comparatively the same in both nutritive value and popularity, but the use of pork has been generally condemned the world over. The reason for this is probably explained by prejudices of tradition and religion, rather than by scientific or hygienic knowledge. The prejudice against swine because of the filthy habits of the animal is more a matter of sentiment than of science. It is sometimes the custom among farmers to confine hogs in a pen, and to feed them upon swill and garbage. This makes of the animal a filthy creature. However, when left in the open fields or woods, they are as cleanly in their habits as any of their brother animals. Corn and alfalfa-fed pork is equally as wholesome as beef or mutton, when prepared in a similar manner, and eaten in temperate quantities, while the hog fattened upon acorns and herbs, in his native habitat (the woods), is much more healthy, and his flesh really superior to most of his brother animals.

2 ANIMAL FATS