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The normal cells of bodies so complex as ours live in an environment of lymph or of blood. The blood is the source of the lymph, so it is not far wrong to say that the blood, by way of the lymph, feeds the body, and is its most vigorous defender in times of danger. Since the blood receives the lymph after it is drained from the cells, it is also true that the blood drains the wastes from the cells, as well as brings them their food. The products of the metabolism of some of the cells of the body are of the most vital importance to other cells, and the products of the metabolism of all the cells may become of great importance in the metabolism of other cells.
The products of the metabolism of the ductless glands, and of many other tissues of the body which furnish an internal secretion, are absolutely essential to the maintenance of normal function of all the other parts of the body. The ill effects of various mutilating operations is largely due to the lack of the normal internal secretions from the removed organs. In many instances, doubtless, the lack of the internal secretion is preferable to the presence of an abnormal organ, which is a menace to life itself, but the cells of the body have lived together so long, and have become so thoroughly adapted to living in an environment composed of one another, that not any organ of the body is to be considered as absolutely without effect upon body metabolism. The substances thrown into the blood by that tissue from time immemorial, and the other cells of the body have become so thoroughly adjusted to this substance, however inert it may seem, that its lack must never be considered a thing of no consequence. The internal secretions of all the tissues of the body affect all other tissues of the body to a certain very variable extent.
The blood plasma carries dissolved in it all the substances needed for the nutrition of every part of the body. Among all the diverse structures of our complex bodies, there is not one which does not find its requisite food stuffs in the blood stream. Yet it must not be considered that the complexity of the tissues which are nourished from the blood is indicative of any comparable complexity of substances found in the blood. The serum compounds are comparatively simple, and from these the cells build up their own variable and complex structures. There are only twenty-six letters in the English alphabet, and yet from these letters, many books, no one like any other one, have been written. Many books contain quotations from other books, and many cells use as foods the substances prepared for them by other cells. Many books are antagonistic to other books, and the compounds formed by some of the cells of the body are toxic to other cells of the same body.
The plasma and all the elements floating in it contain a certain proportion of inorganic salts. These are of considerable importance in the bodily economy, quite apart from their function in supplying these substances in proper amounts to the cells for their food. The osmotic tension of the body fluids varies according to the amount of inorganic salts dissolved in these fluids. The maintenance of the normal interchange of food stuffs and katabolic products between the cell and its environment is very dependent upon the maintenance of a normal equilibrium of internal and external osmotic tension. The blood serum provides these salts to the tissues, and the rapidity of the circulation of the blood prevents an unequal distribution of them, even when the various tissues are undergoing metabolism with very unequal vigor and quality. The function of these inorganic salts and their ions has been made the subject of recent experiments. This work has added much to our appreciation of the exceeding importance of these salts in controlling the activity of the muscles and glands of the body, and in maintaining the blood pressure at a normal point. One of the serum globulins, the fibrinogen, may attract our attention for a little time, because of its importance in maintaining life under circumstances of accident, etc. Under normal conditions, it is simply one of the food stuffs of the cells. But when there is an injury to the blood vessels the fibrinogen, after being acted upon by the ferments set free by the injury, and by the calcium salts, becomes transformed into the fibrin of the familiar blood clot. The body is thus protected from the excessive hemorrhage from slight injuries, and the repair of wounds is facilitated. The formation of the clot is described very fully in the text books on physiology, so further discussion of the matter is not needful here. The corpuscles which float in the blood stream are of great importance in the processes of recovery, no less than in the maintenance of normal metabolism. The erythrocytes are chiefly, if not entirely functional in carrying oxygen. The erythrocytes vary with many nutritive conditions, and the amount of hemoglobin which each one carries is also subject to marked variation in abnormal nutritive conditions, and to some variation even in health. The amount of oxygen which is supplied to the tissue is absolutely dependent upon the amount of hemoglobin present in the blood, provided the supply of oxygen in the air in the lungs is normal.
The character of the katabolic products of the cells of the tissues depends upon the oxygen supply. If oxygen is carried to the tissues in quantities equal to their demands, the katabolic products of the cells are normal,--that is, they are inert, almost harmless substances, usually neutral, or only very faintly acid in reaction. Carbon dioxide, water, urea, etc., are the most familiar of these. A deficient supply of oxygen to the tissues results in the excretion by the cells of partially oxidized compounds, acid or acid-forming compounds which are characteristic of abnormal conditions of metabolism. Some of these acid products are decidedly toxic in their effects, and these are the cause of the symptoms of auto-intoxication, of delirium in some fevers, of coma in diabetes, and of other symptoms produced in conditions of faulty oxidation processes. These acid products reduce the alkalinity of the blood, and thus facilitate the deposits of urates in the joints and elsewhere. The bactericidal power of the blood varies with its alkalinity, partly because the phagocytes are not well nourished when the blood is deficient in the alkaline salts, partly because bacteriolysis depends upon a supply of nascent oxygen, and partly because most bacteria thrive best in an acid or very faintly alkaline medium. A lack of erythrocytes or of the hemoglobin content of the erythrocytes is therefore a serious menace to health.
The phagocytes are, according to Metchnikoff, the most efficient guardians of the body against bacteria and other parasites. They are very efficient in the repair of wounds, also, but they are not helpful in their accustomed manner when the blood stream is not kept well supplied with food and oxygen, or when it is permeated with the toxic substances resulting from abnormal metabolism or the retention of the waste products of normal metabolism.
The blood, with the lymph, acts also as scavenger. If the drainage of any cell or cell group be insufficient, or if the blood be filled with waste products of metabolism, the cells are practically forced to work in the presence of their own katabolic products. Their function is thereby impaired, and, if the abnormal condition be long continued, their structure is impaired also. It is not possible for any cell or cell group to maintain normal function in the presence of its own katabolic products. Even unorganized ferments, non-living as they are, are unable to affect the substances to which they are best adapted in the presence of the products of their past activity. The functions of blood and lymph in removing the products of cell activity are not the least important of their duties.
In order that the blood shall be normal in quantity and quality only a few conditions are needful, unless the patient is suffering from some malignant blood disease. The most important requisite for the maintenance of a plentiful supply of good blood is that the blood shall be kept rapidly moving under a normal pressure. This condition is said to be the most important because if it is present the other conditions are almost sure to follow. For example, if the blood flows freely through the splanchnic region, a normal hunger is almost certain. If the blood flows freely through the lungs, normal breathing is practically assured. If the sensory nerves are freely supplied with blood at normal pressure, they will perforce carry impulses to the nervous system which will assist in orienting the individual into a normal relation with his environment. These things are not absolutely dependent upon the normal circulation, but they are largely affected by these factors.
Even the best conditions of circulation, however, are not enough to keep good blood very long in the absence of proper food. Under normal circumstances, the appetite may be considered a fairly efficient test. But it is scarcely possible to find the really normal appetite. The lives of civilized people are so complex, so hedged about by conventionalities, that it is not at all easy for the unhampered appetite to find appropriate food upon our tables. If foods of the several classes,--fats, proteids, carbohydrates, fruits, etc., were set before us daily from childhood, we should probably choose wisely that which our bodies require. But this condition is not found in the average household. Children are taught a fondness for the most unwholesome foods, and the utmost endeavor of the modern cook seems to be to spoil the greatest possible amount of good food in the preparation of the most injurious dishes short of actual poisoning. Because of this factor in education, and not because of any untrustworthiness on the part of the untrammeled appetite, the study of dietetics is essential to those who endeavor to live the race to higher plane of moral and mental and physical strength. Under abnormal conditions, either of disease or accident, a well chosen diet may add to the blood those elements from which the tissues may be built with the least expenditure of energy by the digestive and eliminating organs. The diet should always be adapted to the requirements of the individual case.
Hemoglobin is derived for the most part from the chlorophyll and chromophyll of plants, and from the hemoglobin and myohematin of flesh used as food. Therefore, these foods are indicated in the presence of a low color index. The use of flesh foods is subject to certain limitations; these should be considered in connection with each case. If any essential element of good blood is lacking, the diet should be so regulated as to supply the foods from which these elements may be built up. It is needless to say that the best of blood cannot supply to the tissues oxygen which is lacking from the air in the lungs. Normal air to be inspired, and normal habits of breathing are essential to good blood.
Coagulation of the Blood, in Tigerstedt’s Physiology, p. 157, Edition of 1906. The Hourly Variations in the Quantity of Hemoglobin and in the Number of Corpuscles in Human Blood. Herbert C. Ward, American Journal of Physiology, Volume XI, No. 4. |