  The expenditures of the human body, or the waste products which arise from the activity of the master tissues, are thrown off by the excretory tissues, as the lungs, the skin, the kidneys, and the terminal part of the intestines. The lungs are hollow organs, and we may consider them as really two bags containing air, each of which communicates by a separate orifice with a common air tube, through the upper part of which, the larynx, they freely communicate with the external atmosphere. The orifice of the larynx is guarded by muscles, and can be opened or closed at will. Each lung is partially subdivided into separate portions called lobes. The right lung has three lobes, and the left lung has two. Each of these lobes, again, is composed of a large number of minute parts, called lobules. Each pulmonary lobule may be considered a lung in miniature, consisting as it does of a branch of a bronchial tube, air-cells, blood-vessels, nerves, and lymphatics, with a sparing amount of areolar tissue. The terminal portion of each lobule is composed of a group of pouches or air-cells, which communicate with the intercellular air passages. These cells are of various forms, according to the mutual pressure to which they are subject. Their cell walls are Outside the cells a network of pulmonary capillaries is spread out so densely that the interspaces or meshes are even narrower than the vessels, which are on an average 1/3000? of an inch in diameter. Between the atmospheric air in the cells and the blood in the vessels nothing intervenes but the thin membrane of the cells and the capillaries, and the delicate epithelium lining the former. And the exposure of the blood to the air is the more complete because the folds of membrane between contiguous cells, and often the spaces between the walls of the same, contain only a single layer of capillaries, both sides of which are thus at once exposed to the air. The enlargement of the capacity of the chest in inspiration is a muscular act; the muscles concerned in producing the effect being chiefly the diaphragm, the external intercostal muscles, etc. From the enlargement produced in inspiration, the chest and lungs return in ordinary tranquil expiration by their elasticity; the force employed by the inspiratory muscles in distending the chest and overcoming the elastic resistance of the lungs and chest wall being returned as an expiratory effort when the muscles are relaxed. The acts of expansion and of contraction of the chest take up, under ordinary circumstances, a nearly equal time, and can scarcely be said to be separated from each other by an intervening pause. The quantity of air that is changed in the lungs in each act of ordinary tranquil breathing is variable, but probably 30 to 35 cubic inches are a fair average in the case of healthy young and middle-aged men. The total quantity of air which passes into and out of the lungs of an adult, at rest, in 24 hours, has been estimated to be about 686,000 cubic inches. This quantity is largely increased by exertion; and Breathing air is the quantity of air which is habitually and almost uniformly changed in each act of breathing. Complemental air is the quantity of air over and above this which a man can draw into the lungs in the deepest inspiration. After ordinary expiration, such as that which expels the breathing air, a certain quantity of air remains in the lungs which may be expelled by a forcible and deeper expiration; this is termed reserve air. But even after the most violent expiratory effort, the lungs are not completely emptied; a certain quantity of air remains in them, over which there is no voluntary control, which may be called residual air. Its amount depends, in great measure, on the absolute size of the chest, and has been variously estimated at from 40 to 200 cubic inches.
The blood as it moves through the respiratory organs is exposed to the air that alternately moves into and out of the air-cells and minute bronchial tubes. The blood is propelled from the right ventricle through the pulmonary capillaries in steady streams, and slowly enough to permit every minute portion of it to be for a few seconds exposed to the air, with only the thin walls of the capillary vessels and air-cells intervening. The atmosphere we breathe has in every situation The changes produced by respiration on the atmosphere are that: 1. It is warmed; 2. Its carbonic acid is increased; 3. Its oxygen is diminished; 4. Its watery vapor is increased; 5. A minute amount of organic matter and of free ammonia is added to it. 1. The expired air is hotter than the inspired air. The temperature varies from 97° to 99½°. 2. Carbonic acid in respired air is always increased; but the quantity exhaled in a given time is subject to change from various circumstances. From every volume of air inspired about 4½ per cent of oxygen is abstracted; while rather a smaller quantity of carbonic acid is added in its place. Under ordinary circumstances, the quantity of carbonic acid exhaled into the air breathed by a healthy adult man amounts to 1,346 inches, or about 636 grains, per hour. It is estimated that the weight of carbon excreted from the lungs is about 173 grains per hour, or rather more than 8 ounces in 24 hours. Of course the influence of age, sex, respiratory movements, external temperature, season of the year, purity of the respired air, hygrometric state of the atmosphere, period of day, food and drink, exercise and sleep, have to be taken in consideration. The oxygen of respired air is always less than in the same air before respiration, and its diminution is generally proportionate to the increase of the The nitrogen in the atmosphere, in relation to the respiratory process is supposed to serve only mechanically, by diluting the oxygen, and moderating the action upon the system. The most obvious change which the blood undergoes in its passage through the lungs is that of color, the dark venous blood being exchanged for the bright scarlet arterial blood. It gains oxygen, loses carbonic acid, becomes 1° to 2° F. warmer; it coagulates sooner and more firmly, and contains more fibrine. The venous blood as it issues from the right ventricle is loaded with carbonic acid. The oxygen present is insufficient to the whole of the hÆmoglobin of the red corpuscles; much reduced hÆmoglobin is present, hence the purple color of venous blood. As the blood-vessels pass through the capillaries of the lungs, this reduced hÆmoglobin takes from the pulmonary air its complement of oxygen, all or nearly all the hÆmoglobin of the red corpuscles becomes oxy-hÆmoglobin, and the purple color forthwith shifts into scarlet. The hÆmoglobin of arterial blood is saturated or nearly saturated with oxygen. Passing from the left ventricle to the capillaries, some of the oxy-hÆmoglobin gives up its oxygen to the tissues, becomes reduced hÆmoglobin, and the blood in consequence becomes once more venous, with a purple hue. Thus the red corpuscles by virtue of their hÆmoglobin are emphatically oxygen-carriers. Undergoing no intrinsic change in itself, the hÆmoglobin combines in the lungs with oxygen, which it carries to the tissues; these, more greedy of the oxygen than itself, rob it of its charge, and Respiratory changes in the tissues. Arterial blood passing through the several tissues, becomes once more venous. A considerable quantity of the oxy-hÆmoglobin becomes reduced, and a quantity of carbonic acid passes from the tissue into the blood. The blood which comes from a contracting muscle, is not only richer in carbonic acid, but also, though not to a corresponding amount, poorer in oxygen, than the blood which flows from a muscle at rest. A muscle is always producing carbonic acid, and when it contracts there is a sudden and extensive increase of the normal production. Oxygen is necessary for the life of the muscle. When venous blood instead of arterial blood is sent through the blood-vessel of a muscle, the irritability speedily disappears, and unless fresh oxygen be administered the muscle soon dies. Our knowledge of the respiratory changes in muscle is more complete than in the case of any other tissue; but we have no reason to suppose the phenomena of muscle are exceptional. On the contrary, all the available evidence goes to show that in all the tissues the oxidation takes place in the tissues and not in the adjoining blood. It is a remarkable fact, that lymph, serous fluid, bile, urine, and the other secretions contain no free or loosely combined oxygen, while the tension of carbonic acid in peritoneal fluid is as high as six per cent, and in bile and urine is still higher, etc. All these facts point to the conclusion, that it is the tissues, and not the blood, which become primarily The production of carbonic acid in the muscle is not directly dependent on the consumption of oxygen. The muscles produce carbonic acid in an atmosphere of hydrogen. What is true of muscle is true also of other tissues and of the body at large. Oxygen helps to wind up the vital clock; but once wound up, the clock will go on for a period without further winding (PflÜger). To sum up, then, the result of respiration in its chemical aspect. As the blood passes through the lungs, the low oxygen tension of the venous blood permits the entrance of oxygen from the air of the pulmonary alveolus, through the thin alveolar wall, through the thin capillary sheath, through the thin layer of blood plasma, to the red corpuscles, and the reduced hÆmoglobin of the venous blood becomes wholly, or all but wholly, oxy-hÆmoglobin. Hurried to the tissues, the oxygen, at a comparatively high tension in the arterial blood, passes largely into the tissues, in which the oxygen tension is always kept at an exceedingly low pitch, by the fact that the tissues, in some way at present unknown to us, pack away, at every moment, into some stable combination each molecule of oxygen which they receive from the blood. With much, but not all, of its oxy-hÆmoglobin reduced, the blood passes on as venous blood. How much hÆmoglobin is reduced will depend on the activity of the tissue itself. The quantity of hÆmoglobin in the blood is the measure of limit of the oxidizing power of the body at large; but within that limit the amount of oxidation is determined by the tissue, and by the tissue alone. The skin is an excretory tissue, and consists principally Sudoriferous glands: In the middle of each of the transverse furrows between the papillÆ, and irregularly scattered between the bases of the papillÆ in those parts of the surface of the body in which there are no furrows between them, are the orifices or ducts of the sudoriferous, or sweat glands, by which it is probable that a large portion of the aqueous and gaseous materials excreted by the skin are separated. Each of these glands consists of a small lobular mass, which appears formed of a coil of tubular gland-duct surrounded by blood-vessels and imbedded in the subcutaneous adipose tissue. From this mass the duct ascends, for a short distance, in a spiral manner through the deeper parts of the cutis, then passing straight, and then sometimes again becoming spiral, it runs through the cuticle and opens by an oblique, valve-like apparatus. The sudoriferous glands are abundantly distributed over the whole surface of the body; but are especially numerous, as well as very large, in the skin of the palm of the hand. They are estimated from 2,738 to 3,528 in each superficial square inch. They are almost equally abundant and large in the skin of the sole. The glands by which the peculiar odorous matter of the axilla is secreted form a nearly complete layer under the cutis, and Sebaceous glands secrete a peculiar fatty matter. Like the sudoriferous glands, they are abundantly distributed over most parts of the body. The quantity of matter which leaves the human body by way of the skin is very considerable. It is estimated that while 7 grains pass through the lungs per minute, as much as 11 escape through the skin. The amount varies extremely. It is calculated that the total amount of perspiration excreted from the whole body in 24 hours might range from 2 to 20 kilos. The total amount of perspiration is affected not only by the condition of the atmosphere, but also by the nature and quantity of food taken, the amount of fluid drunk, and the amount of exercise taken. It is also influenced by the mental condition, by medicines and poisons, by disease, and by the relative activity of the other excreting organs, more particularly the kidneys. The fluid perspiration or sweat, when collected, is found to be a clear colorless fluid, with a strong and distinctive odor varying according to the part of the body from which it is taken. Besides accidental epidermic scales, it contains no structural elements. Its reaction is generally acid, but in cases of excessive secretion may become alkaline. The average amount of solids is about 1.81 per cent, of which about two-thirds consists of organic substances. The chief normal constituents are (1) sodium chloride The average loss by cutaneous and pulmonary exhalation in a minute is from 17 to 18 grains; the minimum, 11 grains; the maximum, 32 grains; of the average 18 grains 11 pass by the skin and 7 by the lungs. The maximum loss by exhalation, cutaneous and pulmonary, in twenty-four hours is about 3¾ pounds; the minimum, about 1½ pounds. Valentine found the whole quantity lost by exhalation from the respiratory and cutaneous surfaces of a healthy man who consumed daily 40,000 grains of food and drink to be 19,000 grains, or 2½ pounds. Subtracting from this, for the pulmonary exhalation, 5,000 grains, and for the excess of the weight of the exhaled carbonic acid over that of the equal volume of the inspired oxygen, 2,256 grains, the remainder, 11,744 grains, or nearly 1?5/7? pounds, may represent an average amount of cutaneous exhalation in a day. The Kidneys, two in number, are excretory organs. They are deeply seated in the lumbar region, one on each side of the vertebral column, at the back of the abdominal cavity, and behind the peritoneum. The kidneys measure about 4 inches in length, 2½ inches in breadth, and 1½ inches in thickness. The left is usually longer and narrower than the right one. The weight of the kidney is usually stated to be about 4½ ounces in the male and somewhat less in the female. The excretory apparatus consists of fine tubules (the tubuli urineferi), malpighian bodies, blood-vessels, nerves, and lymphatics, etc. The kidneys are highly vascular, and receive their blood from the renal arteries, which are very large in proportion to the organ they supply. Each artery The kidneys are so arranged by their anatomical structure—that of the cortical and medullary substance, the tubuli urineferi, pyramids, malpighian bodies, etc.—that they separate from the blood the solids in a state of solution. The secretion takes place by the agency of the gland cells, and equally in all the parts of the urine tubes. The protoplasmic cells which line at least a large portion of the tubuli urineferi elaborate from the blood certain substances, and discharge them into the channels of the tubules. All parts of the tubular system of the kidney take part in the secretion of urine as a whole, but there is another provision of vessels for a more simple draining off of the water from the blood when required. The large size of the renal arteries and veins permits so rapid a transit of the blood through the kidneys that the whole of the blood is purified by them. The secretion of urine is rapid in comparison with other secretions, and as each portion is secreted, it propels that which is already in the tubes onwards into the pelvis of the kidney. Thence, through the ureter, the urine passes into the bladder, into which its rate and mode of entrance has been watched. The urine does not enter the bladder at any regular rate, nor is there a synchronism in its movement through the two ureters. In a recumbent posture the urine collects for a little time in the ureters, then flows gently, and if the body is raised, runs from them in a stream till they are empty. Its flow is increased Substances taken into the stomach pass very rapidly through the circulation. It does not take longer than one minute for ferrocyanide of potassium to pass through. Vegetable substances pass in from sixteen to thirty-five. Neutral alkaline salts with vegetable acids, which were generally decomposed in transitu, made the urine alkaline in twenty-eight to forty-seven minutes. But the time of passage varied much; and the transit was always slow when the substances were taken during digestion. There are really two distinct parts in the kidney—the actively secreting part, the epithelium of the secreting tubules; and what maybe called a filtering part, the malpighian bodies. The specific gravity of urine is 1020—that is, the average human urine. Urine varies—in the morning before breakfast it is darker, urina sanguinis; urine secreted shortly after the introduction of any considerable quantity of fluid into the body, urina potus; and the urine evacuated immediately succeeding a solid meal of food, urina cibi. The last kind contains a larger quantity of solid matter than either of the others, the first and second being largely diluted with water. Specific gravity: The morning urine is best calculated for analysis. The average healthy range may be stated at 1015 in the winter to 1025 in the summer, and variations of diet and exercise may make a great difference. In disease, the variations may be greater; sometimes descending in albuminaria to 1004, and frequently ascending in diabetes, when the urine is loaded with sugar, to 1050, or even to 1060. The whole quantity of urine secreted in twenty-four hours is subject to variations according to the amount of fluid drunk, and the proportion of the The chemical composition of urine. The average quantity of each constituent of the urine in 1,000 parts is:
Urea is the principal solid constituent of the urine, forming nearly one-half of the whole quantity of solid matter. It is also the most important ingredient, since it is the chief substance by which the nitrogen of decomposed tissue and superfluous food is excreted from the body. The salts excreted by the kidneys in 24 hours are:
The substances excreted consist mainly of carbonic acid gas (C O2), which is expired by the lungs, and urea (C N2 H4 O), which is expelled by the urine. These excretions, or expenditures, or waste products The daily average loss by the expenditure or waste products of the body is estimated to be about:
Of all the elements of the income and outcome, the nitrogen, the carbon, and the free oxygen of respiration, are by far the most important. Since water is of use to the body for merely mechanical purposes, and not as food in the strict sense of the word, the hydrogen element becomes a dubious one; the sulphur of the proteids, and phosphorus of the fats, are insignificant in amount; while the saline matters stand on a wholly different footing from the other parts of the food, inasmuch as they are not sources of energy, and pass through the body with comparatively little change. The correct income will consist of so much nitrogen, carbon, hydrogen, oxygen, sulphur, phosphorus, saline matters, and water, contained in the proteids, fats, carbohydrates, salts, and water of the food, together with the oxygen absorbed by the lungs, skin, and alimentary canal. The outcome will consist of: 1. The respiratory products of the lungs, skin, and alimentary canal, consisting chiefly of carbonic acid and water, with small quantities of hydrogen and carburetted hydrogen, these two latter coming exclusively from the alimentary canal; 2. Perspiration, consisting chiefly of water and salts, with urea by the skin, and other organic constituents of sweat amounting to very little; 3. The urine, which contains practically all the nitrogen really excreted by the body, as well as a large quantity of saline matter and water. HEAT AND TEMPERATURE.The average temperature of the human body in those internal parts which are more accessible, as the mouth and rectum, is from 98.5° to 99.5° F. The chief circumstances by which the temperature of the healthy body is influenced are the following: Age. The average temperature of the new-born babe is only about 1° F. above that proper to the adult. In old age the temperature rises again, and approaches that of infancy. Sex. In the female slightly higher than in the male. Exercise. Active exercise raises the temperature of the body, through muscular contraction, etc. Climate and season. In passing from a temperate to a hot climate, the temperature of the human body rises slightly, rarely more than 2° to 3° F. In summer the temperature of the body is a little higher than in winter, ?° to ?° F. Cold alcoholic drinks depress the temperature ½° to 1°F. Warm alcoholic drinks, as well as warm tea and coffee, raise the temperature about ½° F. In disease, as in pneumonia and typhus, it occasionally rises as high as 106° or 107° F. In Asiatic cholera a thermometer placed in the mouth sometimes rises only to 77° or 79° F. The temperature maintained by mammalia of an active state of life averages 101° F. In birds, the average is as high as 107° F., the highest temperature, 111.25°, being in the species of the linnets, etc. The sources and distribution of heat. Wherever metabolism of protoplasm is going on, heat is being generated. All over the body heat is being set free; more abundantly in the more active tissues, and most of all in those tissues the metabolism of which leads to little or no external work. The metabolism of the tissues (including the blood) and of the food within the alimentary canal is the source of the heat of Taking the body as a whole, under normal conditions, the chief sources of the production of heat are the muscles, and the abdominal viscera, more especially the liver; and of these the liver deserves attention, inasmuch as it is always at work, whereas the heat produced by the muscles is at least largely dependent on their contracting, and they may remain at rest for a considerable period. The brain, too, may be regarded as a source of heat, since its temperature is higher than that of the arterial blood with which it is supplied. Heat is lost by the skin, respiration, feces, etc. The great regulator, however, is undoubtedly the skin. The more blood passes through the skin the greater will be the loss of heat by conduction, radiation, and evaporation. The working of this heat-regulating mechanism is well seen in the case of exercise. Since every muscular contraction gives rise to heat, exercise must increase for the time being the production of heat; yet the bodily temperature rarely rises as much as a degree C., if at all. By exercise the respiration is quickened and the loss of heat by the lungs increased. The circulation of blood is also quickened, and the cutaneous vascular areas becoming dilated, a large amount of blood passes through the skin. The expenditure of heat may be tabulated thus:
THE CIRCULATION.The heart is a hollow muscular organ divided by a longitudinal septum into a right and a left half, each of which is again subdivided by a transverse constriction into two compartments communicating with each other, and named auricle and ventricle. The heart is inclosed in the pericardium and placed behind the sternum and costal cartilages on the border end or base, by which it is attached, being directed upwards, backwards, and to the right, and extending from the level of the fourth to that of the eighth dorsal vertebra, the apex downwards, forwards, and to the left. In size, it is about five inches long, three and a half in its greatest width, and two in its extreme thickness from the anterior to the posterior surface. The weight is from nine to ten ounces. The circulation of the blood.— The body is divided into two chief cavities, the chest or thorax, and abdomen, by a curved muscular partition called the diaphragm or midriff. The chest is almost entirely filled with lungs and heart, the latter being fitted in, so to speak, between the two lungs, nearer to the front than the back of the chest, and partly overlapped by them. In the living body the heart and lungs are in constant rhythmic movement, the result of which is an unceasing stream of air through the trachea alternately into and out of the lungs, and an unceasing stream of blood into and out of the heart. The blood is conveyed away from the heart by the arteries and returned to it by the veins; the arteries and veins being continuous with each other, at one There are two circulations by which all the blood must pass—the one a shorter circuit from the heart to the lungs and back again, which is called the pulmonic; the other the larger circuit, from the heart to all parts of the body and back again, which is called the systemic; and a subordinate stream of blood, that has been collected by the blood-vessels of the intestines, passes by means of the portal vein through the liver, and is called the portal circulation. The principal force provided for constantly moving the blood on this course, is that of the muscular substance of the heart; other assistant forces are (2) those of the elastic walls of the arteries, (3) the pressure of the muscles among which some of the veins run, (4) the movements of the walls of the chest in respiration, and (5) probably to some extent the interchange of relations between the blood and the tissues which ensues in the capillary system during the nutritive processes. The right direction of the blood’s course is determined and maintained by the valves of the heart. The heart is divided into two chief chambers or cavities—right and left. Each of these chambers is again divided into an upper and lower portion called respectively auricle and ventricle, which freely communicate with each other. The right auricle communicates on the one hand with the veins of the general system and on the other with the right ventricle. The valvular curtain between the right auricle and the right ventricle is named the tricuspid; by it the auricle is guarded from the ventricle. The ventricle leads directly into the The arrangement of the heart’s valves is such that the blood can pass only in one definite direction, and this is—from the right auricle the blood passes into the right ventricle, and thence into the pulmonary artery, by which it is conveyed to the capillaries of the lungs. From the lungs, the blood, which is now purified and altered in color, is gathered by the pulmonary veins and taken to the left auricle. From the left auricle it passes into the left ventricle, and thence into the aorta, by which it is distributed to the capillaries in every portion of the body. The Heart’s action. The heart’s action in propelling the blood consists in the successive alternate contractions and dilatations of the muscular walls of the two auricles and ventricles. The auricles contract simultaneously; so do the ventricles; their dilatations also are severally simultaneous; and the contractions of the one pair of cavities are synchronous with the dilatations of the other. Valves—Bi and Tricuspid. During auricular contraction the force of the blood propelled into the ventricle is transmitted in all directions, but being insufficient to raise the semilunar valves, it is expended in distending the ventricle and in raising and gradually closing the auriculo-ventricular valves (tricuspid and bicuspid valves). These when the ventricle is full form a complete septum (partition) between it and the auricle. The arterial or semilunar valves are brought into The sounds. When the ear is placed over the region of the heart two sounds may be heard at every beat of the heart, which follow in quick succession, and are succeeded by a pause or a period of silence. The first sound is dull and prolonged; its commencement coincides with the impulse of the heart and just precedes the pulse at the wrist. The second is a shorter and sharper sound, with a somewhat flapping character, and follows close after the arterial pulse. First sound. The chief cause of the first sound of the heart appears to be the vibration of the auriculo-ventricular valve, and also, but to a less extent, of the ventricular walls, and the coats of the aorta and pulmonary artery, all of which parts are suddenly put into a state of tension at the moment of ventricular contraction. The second sound is more complete than that of the first. It is probably due entirely to the sudden closure and consequent vibration of the semilunar valves when they are pressed down across the orifice of the aorta and pulmonary artery. Pulse. The heart of a healthy adult man in the middle period of life acts from seventy to seventy-five times per minute. The frequency of the heart’s action gradually diminishes from the commencement to near the end of life. In persons of sanguine temperament, the heart acts somewhat more frequently than in those of the phlegmatic; and in the female sex more frequently than in the male; in children, more frequently still. Capacity. The capacity of the two ventricles is probably exactly the same. From the mean of various estimates taken, it may be inferred that each Every time the ventricles contract three ounces of blood are pumped out of the heart into the lungs and heart respectively. Calculating seventy pulses per minute, the quantity of blood passing through the heart would be about 211 ounces, or 14¼ pints per minute; or 895 pints per hour, or 21,480 pints in 24 hours. Velocity. The velocity of the stream of blood is greater in the arteries than in any other part of the circulatory system, and in them it is greatest in the neighborhood of the heart and during the ventricular systole; the rate of movement diminishes during the diastole of the ventricles, and in the parts of the arterial system most distant from the heart. The rate is calculated to be about from 10 to 12 inches per second in the large arteries near the heart. THE BLOOD.Blood is a tissue of which the red corpuscles are the essential and active elements, while the plasma is the liquid matrix. There are two kinds of corpuscles, the white and the red. The protoplasm of the white corpuscles is native indifferentiated protoplasm, in no respect fitted for any special duty, as far as we know at present. The white corpuscles are in reality embryonic structures, concerned chiefly in the production of other forms, such as red corpuscles, and it may be under certain conditions various elements of the other tissues. The red corpuscles have a definite respiratory function. But these form a part only of the blood. The largest portion of the blood, the whole mass of the plasma, is an unorganized fluid with no proper physiological (vital) properties of its own. Its function is to serve as the great medium of exchange between all the tissues of the body. Just as the whole organism lives on the things around it, its air and its food, so Blood within the living vessel is a fluid; but when shed, or after the death of the vessels, becomes solid by the process known as coagulation. The average specific gravity of human blood is 1056, varying from 1045 to 1075 within the limits of health. It has an alkaline reaction, which in shed blood rapidly diminishes up to the onset of coagulation. Blood may, in general terms, be considered as consisting by weight of more than one-third and less than one-half of corpuscles, the rest being plasma, the corpuscles being supposed to retain the amount of water proper to them. Human blood: corpuscles 513, plasma 487. The average quantity of fibrine in the human blood is said to be two per cent. Composition of serum: In 100 parts there are in round numbers:
Of the proteid substances the great mass consists of the so-called serum-albumen. Composition of red corpuscles: The red corpuscles contain less water than the serum. In 100 parts of red corpuscle there are:
The solids are almost entirely organic matter, the inorganic salts in the corpuscles amounting to less than 4 per cent. In 100 parts of dried organic matter of the corpuscles of human blood there are:
The blood is distributed as follows in round numbers:
The average proportion of the principal constituents of the blood in 1,000 parts is:
The chemical composition of hÆmoglobin is:
THE ORGANS OF RESPIRATION.The principal organs of respiration consist of larynx, trachea, bronchi, lungs. The larynx is affixed to the upper end of the windpipe, and is not only the entrance for air into the respiratory organs from the pharynx, but also the organ of voice. The trachea measures from four inches to four inches and a half in length, and from three-quarters of an inch to one inch in width; but its length and width are liable to continual variations, according to the position of the larynx and the direction of the neck. The trachea divides into two branches, called bronchi, right and left. The right bronchus, wider and shorter than the left, measuring about an inch in length, passes outwards almost horizontally into The lungs, placed one on the right and the other on the left of the heart and large vessels, occupy by far the larger part of the cavity of the chest, and during life are always in accurate contact with the internal surface of its walls. Each lung is attached at a comparatively small part of its flattened inner or median surface by a part named the root and by a thin membranous fold, which is continued downwards from it. The pleurÆ are serous membranes forming two shut sacs, quite distinct from each other, which line the right and left side of the thorax, forming by their approximation in the middle line the mediastinal partition, and are reflected each upon the root and over the entire free surface of the corresponding lung. The lungs. Each lung is irregularly pyramidal or conical, with its base downwards, and one side (the inner) much flattened. The broad concave base is of a semi-lunar form, and rests upon the arch of the diaphragm. The apex is blunt, and reaches into the root of the neck, above the first rib, where it is separated from the first portion of the subclavian artery by the pleural membrane. The lungs vary much in size and weight, according to the quantity of blood and mucous or serous fluid they may happen to contain, which is greatly influenced by the circumstances immediately preceding death, as well as other causes. The weight of both lungs together, as generally stated, ranges from 30 to 48 ounces, the more prevalent weights being found between 36 and 42 ounces. The proportion The average weight in twenty-nine cases, male and female:
The proportionate weight of the lungs to the body is:
The substance of the lungs is of a light porous spongy texture, and when healthy is buoyant in water. Specific gravity, 0.126; deprived of air, 1.056. When pressed between the fingers, the lungs impart a crepitant sensation, which is accompanied by a peculiar noise, both effects being caused by the air contained in the tissue. On cutting the lung the same crepitation is heard. The pulmonary tissues are endowed with great elasticity, in consequence of which the lungs collapse to about one-third of their bulk when the thorax is opened. The root of each lung consists of bronchi, arteries, and veins, together with the nerves, lymphatic vessels, and glands, connected by areolar tissue, and inclosed in a sheath of the pleura. Respiration consists of an expiration and an inspiration. The air passes in through the nose or Inspiration: By the contraction of certain muscles, the cavity of the thorax is enlarged; in consequence the pressure of the air within the lungs becomes less than that of the air outside the body, and this difference of pressure causes a rush of air through the trachea into the lungs until an equilibrium of pressure is established between the air inside and that outside the lungs. This constitutes inspiration. Expiration: Upon the relaxation of the inspiratory muscles (the muscles whose contraction has brought about the thoracic expansion), the elasticity of the chest walls and lungs, aided by the contraction of certain muscles and other circumstances, causes the chest to return to its original size, or even become smaller. In consequence of this the pressure within the lungs now becomes greater than that outside, and thus air rushes out of the trachea, until equilibrium is once more established. This constitutes expiration. The inspiratory and expiratory act together form a respiration. The fresh air introduced into the upper part of the pulmonary passages by the inspiratory movement contains more oxygen and less carbonic acid than the old air previously present in the lungs. By diffusion the new or tidal air, as it is frequently called, gives up the oxygen to, and takes carbonic acid from, the old or stationary air, and thus when it leaves the chest in expiration has been the means both of introducing oxygen into and of removing carbonic acid from it. By this ebb and flow of the tidal air and the diffusion between it and the stationary air, the air in the lungs is being continually renewed, through the alternate expansion and contraction of the chest. In what may be considered normal breathing, the respiratory act is repeated When the ordinary respiratory movements prove insufficient to effect the necessary changes in the blood, their rhythm and character become changed. Normal respiration gives place to labored respiration, and this in turn to dyspnoea, which unless some restorative event occurs terminates in asphyxia. Changes of the air in respiration: 1. The temperature of the expired air is variable, but under ordinary circumstances is higher than that of the inspired air. 2. The expired air is loaded with aqueous vapor. 3. The expired air contains about 4 to 6 per cent less oxygen and about 4 per cent more carbonic acid than the inspired air, the quantity of nitrogen suffering but little change. Thus:
While the air in passing in and out of the lungs is thus robbed of a portion of its oxygen, and loaded with a certain quantity of carbonic acid, the blood as it streams along the pulmonary capillaries undergoes important correlative changes. As it leaves the right ventricle it is venous blood of a dark purple or maroon color; when the blood has passed through the lungs and falls into the left auricle, it is arterial blood of a bright scarlet hue. In passing through the capillaries of the body from the left to the right side of the heart, it is again changed from the arterial to the venous condition. The average composition of this gas in the two kinds of blood is as follows. From 100 volumes may be obtained:
Oxygen plays a most important role on this terrestrial globe. Life, health, and food depend on it. This element penetrates, pervades, everything and everywhere, unites and disunites with all other elements, preserves and destroys. While its absence from a living being, whether plant or animal, is death. When a liquid such as water is exposed to an atmosphere containing a gas such as oxygen, some of the oxygen will be dissolved in the water, that is to say will be absorbed from the atmosphere. The quantity which is so absorbed will depend on the quantity of oxygen which is in the atmosphere above; that is to say, on the pressure of the oxygen; the greater the pressure of the oxygen, the larger the amount which will be absorbed. If, on the other hand, water containing a good deal of oxygen dissolved in it be exposed to an atmosphere containing little or no oxygen, the oxygen will escape from the water into the atmosphere. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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