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BODY AND PHYSIOLOGICAL ACTIVITIES
WE ARE conscious of existing, of possessing an activity of our own, a personality. We know that we are different from all other individuals. We believe that our will is free. We feel happy or unhappy. These intuitions constitute for each of us the ultimate reality.
Our states of consciousness glide through time as a river through a valley. Like the river, we are both change and permanence. We are independent of our environment, much more so than are the other animals. Our intelligence has set us free. Man is, above all, the inventor of tools, arms, and machines. With the aid of these inventions he was able to manifest his specific characteristics, and to distinguish himself from all other living beings. He has expressed his inner tendencies in an objective manner by erecting statues, temples, theaters, cathedrals, hospitals, universities, laboratories, and factories. He has, in this way, stamped the surface of the earth with the mark of his fundamental activities--that is, of his esthetic and religious feelings, his moral sense, his intelligence, and his scientific curiosity.
This focus of mighty activities can be observed from within or from without. Seen from within, it shows to the lone observer, who is our self, his own thoughts, tendencies, desires, joys, and sorrows. Seen from without, it appears as the human body, our own, and also that of all our fellow creatures. Thus, man assumes two totally different aspects. For this reason, he has been looked upon as being made up of two parts, the body and the soul. However, no one has ever observed a soul without a body, or a body without a soul. Only the outer surface of our body is visible to us. We perceive our functional activities as a vague sense of well-being. But we are not conscious of any of our organs. The body obeys mechanisms entirely hidden from us. It discloses its constitution only through the techniques of anatomy and physiology. Then, a stupendous complexity appears under its seeming simplicity. Man never allows himself to be observed simultaneously in his outer and public aspect, and in his inner and private one. Even if we penetrate the inextricable maze of the brain and the nervous functions, nowhere do we meet with consciousness. Soul and body are creations of our methods of observation. They are carved by those methods from an indivisible whole.
This whole consists of tissues, organic fluids, and consciousness. It extends simultaneously in space and in time. It fills the three dimensions of space, and that of time with its heterogeneous mass. However, it is not comprised fully within these four dimensions. For consciousness is located both within the cerebral matter and outside the physical continuum. The human being is too complex to be apprehended in his entirety. We have to divide him into small parts by our methods of observation. Technological necessity obliges us, therefore, to describe him as being composed of a corporal substratum and of various activities. And also to consider separately the temporal, adaptive, and individual aspects of these activities. At the same time we must avoid making the classical errors of reducing him to a body, or a consciousness, or an association of both, and of believing in the concrete existence of the parts abstracted from him by our mind.
The human body is placed, on the scale of magnitudes, halfway between the atom and the star. According to the size of the objects selected for comparison, it appears either large or small. Its length is equivalent to that of two hundred thousand tissue cells, or of two millions of ordinary microbes, or of two billions of albumin molecules, placed end to end. Man is gigantic in comparison with an electron, an atom, a molecule or a microbe. But, when compared with a mountain, or with the earth, he is tiny. More than four thousand individuals would have to stand one upon the other in order to equal the height of Mount Everest. A terrestrial meridian is approximately equivalent to twenty millions of them placed end to end. Light, as is well known, travels about one hundred and fifty million times the length of our body in one second. The interstellar distances are such that they have to be measured in light years. Our stature, in relation to such a system of reference, becomes inconceivably small. For this reason, Eddington and Jeans, in their books of popular astronomy, always succeed in impressing their readers with the complete insignificance of man in the universe. In reality, our spatial greatness or smallness is without importance. For what is specific of man has no physical dimensions. The meaning of our presence in this world assuredly does not depend upon our size.
Our stature seems to be appropriate to the character of the tissue cells, and to the nature of the chemical exchanges, or metabolism, of the organism. As nerve impulses propagate in everybody at the same speed, men of a very much larger frame than ours would have too slow a perception of external things, and their muscular reactions would be too sluggish. At the same time the rate of their chemical exchanges would be profoundly modified. It is well known that the metabolism of large animals is lower than that of small ones. The horse, for instance, has a lesser metabolic activity than the mouse. A great increase in our stature would diminish the intensity of our exchanges. And probably deprive us of our agility and of the rapidity of our perceptions. Such an accident will not happen, because the size of human beings varies only within narrow limits. The dimensions of our body are determined simultaneously by heredity and developmental conditions. In a given race, one observes tall and short individuals. These differences in the length of the skeleton come from the state of the endocrine glands and from the correlation of their activities in space and time. They are of profound significance. It is possible, by means of proper diet and mode of living, to augment or diminish the stature of the individuals composing a nation. Likewise, to modify the quality of their tissues and probably also of their mind. We must not blindly change the dimensions of the human body in order to give it more beauty and muscular strength. In fact, seemingly unimportant alterations of our size and form could cause profound modifications of our physiological and mental activities. There is no advantage in increasing man's stature by artificial means. Alertness, endurance, and audacity do not grow with the volume of the body. Men of genius are not tall. Mussolini is of medium size, and Napoleon was short.
Each man is characterized by his figure, his way of carrying himself, the aspect of his face. Our outward form expresses the qualities, the powers, of our body and our mind. In a given race, it varies according to the mode of life of the individuals. The man of the Renaissance, whose life was a constant fight, who was exposed continuously to dangers and to inclemencies, who was capable of as great an enthusiasm for the discoveries of Galileo as for the masterpieces of Leonardo da Vinci or Michelangelo, did not resemble modern man who lives in a steam-heated apartment, an air-conditioned office, a closed car, who contemplates absurd films, listens to his radio, and plays golf and bridge. Each epoch puts its seal on human beings. We begin to observe the new types created by motor-cars, cinemas, and athletics. Some, more frequent in Latin countries, are characterized by an adipose aspect, flabby tissues, discolored skin, protruding abdomen, thin legs, awkward posture, unintelligent and brutal face. Others appear, especially among Anglo-Saxons, and show broad shoulders, narrow waist, and birdlike cranium. Our form is molded by our physiological habits, and even by our usual thoughts. Its characteristics are partly due to the muscles running under the skin or along the bones. The size of these muscles depends on the exercise to which they are submitted. The beauty of the body comes from the harmonious development of the muscles and the skeleton. It reached the height of perfection at the epoch of Pericles, in the Greek athletes whom Phidias and his disciples immortalized in their statues. The shape of the face, the mouth, the cheeks, the eyelids, and the lines of the visage are determined by the habitual condition of the flat muscles, which move in the adipose tissue underlying the skin. And the state of these muscles depends on that of our mind. Indeed, each individual can give his face the expression that he chooses. But he does not keep such a mask permanently. Unwittingly, our visage progressively models itself upon our states of consciousness. With the advance of age it becomes more and more pregnant with the feelings, the appetites, and the aspirations of the whole being. The beauty of youth comes from the natural harmony of the lineaments of the human face. That, so rare, of an old man, from his soul.
The visage expresses still deeper things than the hidden activities of consciousness. In this open book one can read not only the vices, the virtues, the intelligence, the stupidity, the feelings, the most carefully concealed habits, of an individual, but also the constitution of his body, and his tendencies to organic and mental diseases. In fact, the aspect of bones, muscles, fat, skin, and hair depends on the nutrition of tissues. And the nutrition of tissues is regulated by the composition of blood plasma, that is, by the activity of the glandular and digestive systems. The state of the organs is revealed by the aspect of the body. The surface of the skin reflects the functional conditions of the endocrine glands, the stomach, the intestines, and the nervous system. It points out the morbid tendencies of the individual. In fact, people who belong to different morphological classes--for instance, to the cerebral, digestive, muscular, or respiratory types--are not liable to the same organic or mental diseases. There are great functional disparities between tall and spare men, and broad and short ones. The tall type, either asthenic or athletic, is predisposed to tuberculosis and to dementia praecox. The short, pycnic type, to cyclic mania, diabetes, rheumatism, and gout. In the diagnosis and prognosis of diseases, ancient physicians, quite rightly, attributed great importance to temperament, idiosyncrasies, and diatheses. Each man bears on his face the description of his body and his soul.
The skin, which covers the outer surface of the body, is impermeable to water and to gases. It does not allow the microbes living on its surface to enter the organism. It is capable of destroying them with the aid of substances secreted by its glands. But it can be crossed by the minute and deadly beings, which we call viruses. Its external face is exposed to light, wind, humidity, dryness, heat, and cold. Its internal face is in contact with an aquatic world, warm and deprived of light, where cells live like marine animals. Despite its thinness, the skin effectively protects the organic fluids against the unceasing variations of cosmic surroundings. It is moist, supple, extensible, elastic, durable. Its durability is due to its mode of constitution, to its several layers of cells, which slowly and endlessly multiply. These cells die while remaining united to one another like the slates of a roof--like slates ceaselessly blown away by the wind and continually replaced by new slates. The skin, nevertheless, retains its moistness and suppleness, because small glands secrete on its surface both water and fatty substances. At the nostrils, mouth, anus, urethra, and vagina, it joins the mucosas, those membranes that cover the inner surface of the body. All its orifices, with the exception of the nostrils, are closed by elastic and contractile rings, the sphincters. Thus, it is the almost perfectly fortified frontier of a closed world.
Through its outer surface, the body enters into communication with all the things of the cosmic universe. In fact, the skin is the dwelling-place of an immense quantity of small receptor organs, each of which registers, according to its own structure, the changes taking place in the environment. Tactile corpuscles scattered all over its surface are sensitive to pressure, to pain, to heat, or to cold. Those situated in the mucosa of the tongue are affected by certain qualities of food, and also by temperature. Air vibrations act on the extremely complex apparatus of the internal ear by the medium of the tympanic membrane and the bones of the middle ear. The network of olfactory nerves, which extends into the nasal mucous membrane, is sensitive to odors. A strange phenomenon occurs in the embryo. The brain causes a part of itself, the optic nerve and the retina, to shoot out toward the surface of the body. The part of the skin overlying the young retina undergoes an astonishing modification. It becomes transparent, forms the cornea and the crystalline lens, and unites with other tissues to build up the prodigious optical system which we call the eye. The brain is, thus, enabled to record the electromagnetic waves comprised between red and violet.
Innumerable nerve fibers radiate from all these organs and connect them with the spinal cord and the brain. Through the agency of these nerves the central nervous system spreads like a web over the entire surface of the body where it enters into contact with the outer world. The aspect of the universe depends on the constitution of the sense organs, and on their degree of sensitiveness. For instance, should the retina record infra-red rays of great wave length, nature would take on a different visage. The color of water, rocks, and trees would vary with the seasons because of the changes in the temperature. July's clear days, when the smallest details of the landscape stand out sharply against dark shadows, would be obscured by a reddish haze. Heat rays, being visible, would conceal all objects. In winter, the atmosphere would become clear and the contours of things precise. The aspect of men, however, would remain very different. Their outline, vague. Their face, hidden by a red mist issuing from their mouth and nostrils. After violent exercise, the body would seem to increase in size, on account of the heat released by the skin and surrounding the figure with a larger aura. In a like manner, the cosmic world would assume another appearance if the retina became sensitive to ultra-violet rays and the skin to light rays. Or if the acuteness of all our sense organs were considerably augmented.
We ignore things which have no action on the nerve endings of the surface of the skin. Therefore, we do not perceive cosmic rays, although they pass right through our body. It seems that everything reaching the brain has to enter the sensory organs--that is, to influence the nervous layer enveloping our body. The unknown agent of telepathic communications is perhaps the only exception to this rule. In clairvoyance, it looks as though the subject directly grasps the external reality without the help of the usual nerve channels. But such phenomena are rare. As a rule, the senses are the gateway through which the physical and psychological universe penetrates our organism. Thus, the quality of an individual partly depends on that of his surface. For the brain is molded by the continual messages it receives from the outer world. Therefore, the state of our envelope should not be modified thoughtlessly by new habits of life. For instance, we are far from knowing completely what effect exposure to sun rays has upon the development of the entire body. Until the exact nature of this effect has been ascertained, nudism and exaggerated tanning of the skin by natural light, or by ultra-violet rays, should not be blindly accepted by the white races. The skin and its appendages play the part of a faithful keeper of our organs and our blood. They allow certain things to enter our inner world and exclude others. They are the ever open, though carefully watched, door to our central nervous system. They must be looked upon as being an essential part of ourselves.
Our internal frontier begins at the mouth and the nose, and ends at the anus. Through these openings the outside world penetrates into the respiratory and digestive systems. While the skin is impervious to water and to gas, the mucous membranes of the lungs and of the intestines allow these substances to pass. They are responsible for the chemical continuity of our body with its surroundings. Our inner surface is far larger than that of the skin. The area covered by the flat cells of the pulmonary alveoli is immense. It is approximately equal to five hundred square meters. The thin membrane formed by these cells is traversed by oxygen from the air and by carbon dioxide from the venous blood. It is easily affected by poisonous gases and by bacteria, and more particularly by pneu-mococci. Atmospheric air, before reaching the pulmonary alveoli, passes through the nose, the pharynx, the larynx, the trachea, and the bronchi, where it is moistened and freed from dust and microbes. But this natural protection is now insufficient because the air of cities has been polluted by coal dust, gasoline fumes, and bacteria set free by the multitude of human beings. Respiratory mucosa is much more delicate than skin. It is defenseless against strong irritants. Its fragility may cause entire populations to be exterminated by toxic gases in the great wars of the future.
From mouth to anus, the body is traversed by a stream of nutritive substances. The digestive membranes determine the nature of the chemical relations between the external world and the inner world of our tissues and organic fluids. But their functions are far more complex than those of the respiratory ones. They must profoundly transform the foodstuffs which reach their surface. They are not only a filter, but also a chemical factory. The ferments secreted by their glands collaborate with those of the pancreas in decomposing the aliments into substances capable of being absorbed by the intestinal cells. The digestive surface is extraordinarily vast. The mucosas secrete and absorb large quantities of fluids. Their cells allow the foodstuffs, when digested, to enter the body. But they resist the penetration of the bacteria that swarm in the digestive tract. These dangerous enemies are generally held in control by the thin intestinal membrane, and the leucocytes defending it. But they are always a menace. Viruses thrive in the pharynx and the nose. Streptococci, staphylococci, and microbes of diphtheria in the tonsils. The bacilli of typhoid fever and of dysentery multiply with ease in the intestines. The soundness of the respiratory and digestive membranes governs, in a large measure, the resistance of the organism to infectious diseases, its strength, its equilibrium, its effectivity, its intellectual attitude.
Thus, our body constitutes a closed universe, limited on one side by the skin, and on the other by the mucosas covering our inner surfaces. If these membranes are impaired at any point, the existence of the individual is endangered. Even a superficial burn, when extending over a large area of the skin, results in death. This covering separates our organs and humors from the cosmic environment, and yet allows most extensive physical and chemical communications between these two worlds. It accomplishes the miracle of being a barrier at once closed and open. For it does not protect our nervous system against our mental surroundings. We may be wounded, and even killed, by subtle enemies which, ignoring our anatomical frontiers, invade our consciousness, like aviators bombarding a city without taking any notice of its fortifications.
The inside of our body does not resemble the descriptions of classical anatomy. This science has constructed a schema of the human being that is purely structural and quite unreal. It is not merely by opening a corpse that one may learn how man is constituted. Of course, we can observe in this way his framework, the skeleton and the muscles, which are the scaffold of the organs. In a cage formed by the spinal column, the ribs, and the sternum, are suspended the heart and the lungs. The liver, spleen, kidneys, stomach, intestines, and sexual glands are attached, by the folds of the peritoneum, to the inner surface of a large cavity whose bottom is formed by the pelvis, the sides by the abdominal muscles, and the roof by the diaphragm. The most fragile of all the organs, the brain and the cord, are enclosed in osseous boxes, the cranium and the spine. They are protected against the hardness of the walls of their lodgings by a system of membranes and a cushion of liquid.
One cannot understand the living being by studying a dead body. For the tissues of a corpse have been deprived of their circulating blood and of their functions. In reality, an organ separated from its nutritive medium no longer exists. In the living body, blood is present everywhere. It pulsates in the arteries, glides through the veins, fills the capillary vessels, bathes all tissues in transparent lymph. In order to apprehend this inner world as it is, more delicate techniques than those of anatomy and of histology are indispensable. We must study organs of living animals and of men, as they are seen in the course of surgical operations, and not simply those of cadavers prepared for dissection. Their structure should be learned, both from microscopical sections of dead tissues more or less modified by fixatives and dyes, and from living tissues while functioning. Also from cinematographic films on which their movements have been recorded. We must not separate cells from medium and function from structure, as anatomy has done.
Within the body, the cells behave like small organisms plunged in an aerated and nutritive medium. This medium is analogous to sea water. However, it contains a smaller quantity of salts, and its composition is much richer and more varied. The leucocytes of the blood and the cells covering the walls of blood vessels and lymphatics are like fish swimming freely in the depth of the ocean or lying flat on the sandy bottom. But the cells forming the tissues do not float in a fluid. They are comparable, not to fish, but to amphibia inhabiting marshes or moist sand. All living cells depend absolutely on the medium in which they are immersed. They modify this medium unceasingly, and are modified by it. In fact, they are inseparable from it. As inseparable as their body is from its nucleus. Their structure and functions are entirely subordinated to the physical, physicochemical, and chemical conditions of the surrounding fluid. This fluid is the interstitial lymph which at once produces, and is produced by, blood plasma. Cells and medium, structure and function, cannot be separated from one another. The isolation of cells from their natural environment is altogether unwarranted. However, methodological necessity forces us to divide this ensemble into fragments, and to describe, on one side, the cells and tissues, and, on the other, the organic medium--that is, the blood and the humors.
The cells congregate in societies, which are called tissues and organs. But the analogy of these societies to human and insect communities is quite superficial. For the individuality of cells is much less definite than that of men and even of insects. The rules of these associations are merely the expression of the inherent properties of the individuals. The characteristics of human beings are more easily learned than those of their societies. Physiology is a science. Human sociology is not. On the contrary, cell sociology is more advanced than the science of the structure and functions of the cell as an individual. Anatomists and physiologists have long since known the characteristics of tissues and organs--that is, of cell societies. Only recently have they succeeded in analyzing the properties of the cells themselves, of the individuals making up the organic associations. Owing to the new procedures for the cultivation of tissues, it has been possible to study living cells in a flask as easily as bees in a hive. Those cells have revealed themselves as endowed with unsuspected powers, with astounding properties. Virtual in the normal conditions of life, these properties actualize under the influence of diseases, when the organic medium undergoes certain physicochemical changes. These functional characteristics, far more than their structure, give to tissues the power of building up the living body.
Despite its minuteness, each cell is a very complex organism. It does not in any way resemble the favorite abstraction of chemists, a drop of gelatin surrounded by a semi-permeable membrane. The substance, which biologists call protoplasm, is found neither in its nucleus nor in its body. Protoplasm is a concept deprived of objective meaning. Just as the concept anthropoplasm would be, if by such a concept one attempted to define the content of the human body. Cells can now be filmed and magnified to such an extent that, when thrown on the screen, they are larger than a man. All their organs are then visible. In the middle of their body floats a kind of ovoid, elastic-walled balloon, the nucleus, which appears to be full of an inert and transparent jelly. In this jelly are seen two nucleoli, which slowly and unceasingly change their shape. Around the nucleus there is a great agitation of small particles. The movements are particularly active around a cluster of vesicles, corresponding to the organ called by anatomists the apparatus of Golgi or of Renaut, and whose functions are connected with the nutrition of the cell. Small and indistinct granules form a kind of whirlpool in that same district. Larger globules endlessly zigzag through the cell, going as far as the extremities of its mobile and transitory arms. But the most remarkable organs are long filaments, the mitochondrias, which resemble snakes or, in certain cells, short bacteria. Vesicles, granulations, globules, and filaments glide, dance, and undulate perpetually in the free spaces of the cell body.
This structural complexity of the living cell is disconcerting, but its chemical constitution is still more intricate. The nucleus, which, with the exception of the nucleoli, appears to be completely empty, contains substances of a truly marvelous nature. The simplicity attributed by chemists to its constituent nu-cleoproteins is an illusion. In fact, the nuclear substance comprises the genes, those mysterious beings of which we know nothing except that they are the hereditary tendencies of cells and of men. Instead of being simple, the chemical composition of the nucleus must be of bewildering complexity. The genes are generally invisible. However, we know that they dwell in the chromosomes, those elongated bodies seen in the clear fluid of the nucleus when the cell is going to divide. At this moment the chromosomes form in a more or less distinct manner two groups. These groups move away from each other. At the same time, the entire cell shakes violently, tosses its contents in all directions, and divides into two parts. These parts, the daughter cells, withdraw from each other while still united by some elastic filaments. These filaments stretch and finally give way. Thus, two new elements of the organism have become individualized.
Cells, like animals, belong to many different races. These races, or types, are defined by both their structural and their functional characteristics. They spring from different fields, such as the thyroid gland, the spleen, the skin, the liver, etc. But, strange to say, cells originating from the same region may assume different types at successive periods of time. The organism is as heterogeneous in time as in space. The cell types that build up the body may be roughly divided into two classes. The fixed cells, whose associations form the tissues and the organs, and the mobile cells, which travel throughout the entire organism. The connective and epithelial types of cells belong to the fixed category. Epithelial cells are the noblest elements of the body. They constitute the brain, the skin, the endocrine glands, etc. Connective cells build up the framework of the organs. They are truly ubiquitous. Around them appear various substances, such as cartilage, calcium, fibrous tissue, elastic fibers, which give skeleton, muscles, blood vessels, and organs the solidity and elasticity indispensable to their functions. In addition, they metamorphose into contractile elements. These are the muscles of the heart, of the vessels, of the digestive apparatus, and also of the locomotive system. Although connective and epithelial cells seem to be immobile and are still called by their old name of fixed cells, nevertheless they move, as cinematography has shown. But their movements are slow. They glide in their medium like oil spreading over the surface of water. They drag with them their nucleus, suspended in the fluid mass of their body. They differ markedly from the mobile cells. Those cells include the different types of leucocytes of the blood and of the tissues. Their motion is rapid. The leucocytes, characterized by the presence of several nuclei, resemble amebas. The lymphocytes crawl more slowly, like small worms. The larger ones, the monocytes, have the appearance of an octopus. They extrude long tentacles from their substance, and also surround themselves with a thin, undulating membrane. After having enveloped dead cells and microbes in the folds of this membrane, they voraciously devour them.
When these different cell types are bred in flasks, their characteristics become just as apparent as those of the various kinds of microbes. Each type has its own inherent properties, which remain specific, even when several years have elapsed since its separation from the organism. Cell types are characterized by their mode of locomotion, their way of associating with one another, the aspect of their colonies, the rate of their growth, their response to various chemicals, the substances they secrete, the food they require, as well as by their shape and structure. This broader conception is taking the place of the purely morphological definitions of classical anatomy. The laws of organization of each cell community--that is, of each organ --derive from these elementary properties. Tissue cells, possessing only the characteristics ascribed to them by anatomy, would be incapable of building up a living organism. But they are endowed with much higher powers. They do not manifest all of them. Besides the activities which they usually display, they possess others, generally hidden, but capable of becoming actual in response to certain changes of the medium. They are thus enabled to deal with the unforeseeable events taking place in the course of normal life and during illnesses.
Cells unite in dense masses, the tissues and organs, whose architectonic depends on the structural and functional needs of the organism in its totality. The human body is a compact and mobile unit. And its harmony is assured by both the blood and the nerves which integrate all cell communities. The existence of tissues cannot be conceived without that of a fluid medium. The necessary relations of the anatomical elements and of the vessels carrying this nutritive medium determine the shape of the organs. Such shape also is influenced by the presence of the ducts through which glandular products are secreted. All spatial ordering of bodily structures is commanded by their food requirements. The architectural plan of each organ is inspired by the need of the cells to be immersed in a medium always rich in foodstuffs and never encumbered by waste products.
The organic medium is a part of the tissues. Should it be removed, the body would cease to exist. Every manifestation of the life of our organs and nervous centers, our thoughts, our affections, the cruelty, the ugliness, and the beauty of the universe, its very existence, depend on the physicochemical state of our humors. The organic medium is composed of blood, flowing in the vessels, and of fluids, plasma or lymph, which filter through the walls of the capillaries into the tissues. There is a general organic medium, the blood, and regional media, consisting of the interstitial lymph of each organ. An organ may be compared to a pond completely filled with aquatic plants and fed by a small brook. The almost stagnant water is polluted by waste products, dead fragments of plants, and chemical substances set free by them. The degree of stagnation and of pollution of the water depends on the rapidity and the volume of the brook. Such is the case with interstitial lymph. In short, the composition of the regional media inhabited by the various cells of the body rests, directly or indirectly, on blood.
The blood is a tissue, like all the other tissues. It is composed of about twenty-five or thirty thousand billions of red cells, and of fifty billions of white cells. But these cells are not, like those of the other tissues, immobilized in a framework. They are suspended in a viscous liquid, the plasma. Blood is a moving tissue, finding its way into all parts of the body. It carries to each cell the proper nourishment. Acting, at the same time, as a main sewer that takes away the waste products set free by living tissues. It also contains chemical substances and cells capable of repairing organs wherever necessary. These properties are indeed strange. When carrying out such astonishing duties, the blood stream behaves like a torrent which, with the help of the mud and the trees drifting in its stream, would set about repairing the houses situated on its banks.
Blood plasma is not exactly what chemists believe it to be. It is incomparably richer than the classical abstractions. Without any doubt, plasma really is the solution of bases, acids, salts, and proteins, whose physicochemical equilibria are expressed in the laws discovered by Van Slyke and Henderson. Owing to this particular composition, its ionic alkalinity is maintained near the neutral point, in spite of the acids ceaselessly liberated by the tissues. In this manner it supplies all the cells of the entire organism with an unvarying medium, neither too acid nor too alkaline. But it also contains proteins, polypeptides, amino acids, sugars, fats, enzymes, metals in infinitesimal quantities, and the secretions of all glands and tissues. The nature of the majority of these substances is still very imperfectly known. We are scarcely beginning to understand the immense complexity of their functions. Each cell type finds in the blood plasma the foodstuffs indispensable to its maintenance, and also substances accelerating or retarding its activity. Thus, certain fatty compounds linked to the proteins of serum are capable of curbing cellular proliferation, and even of preventing it completely. The serum also contains substances opposing the multiplication of bacteria, the antibodies. These antibodies appear when the tissues have to defend themselves against invading microbes. In addition, there is in blood plasma a protein fibrinogen, father of fibrin, whose shreds spontane-ously adhere to the wounds of blood vessels and stop hemorrhages.
Red and white corpuscles play an important part in the constitution of the organic medium. We know that blood plasma dissolves only a small amount of atmospheric oxygen. Without the help of the red corpuscles, it would, therefore, be incapable of supplying the immense population of body cells with the oxygen they require. These red corpuscles are not living cells. They are tiny sacks full of hemoglobin. During their passage through the lungs they take on a load of oxygen which, a few instants later, they hand over to the greedy tissue cells. When taking delivery of the oxygen, these cells simultaneously get rid of their carbon dioxide and other waste products by passing them on to the blood. The white corpuscles, on the contrary, are living organisms. Sometimes they float in the blood stream, sometimes they escape from the capillary vessels by slipping through their walls into the tissues, and creep on the surface of the cells of the mucous membranes, of the intestines, of the glands, and of all the organs. Owing to these microscopic elements, the blood acts as a mobile tissue, a repairing agent, a medium both solid and fluid, capable of going wherever its presence may be necessary. It can rapidly surround microbes attacking a region of the organism with a great mass of leucocytes, which fight the infection. It also brings to the surface of a wound of the skin or of any organ white corpuscles of the larger type, virtual material for the reconstruction of tissues. Such leucocytes have the power of transforming themselves into fixed cells. And those cells call connective fibers into being, and repair the injured tissues by means of a scar.
The fluids that escape from the capillary vessels constitute the local medium of tissues and organs. It is practically impossible to study the composition of this medium. However, when dyes, whose color changes with the ionic acidity of the tissues, are injected into the organism, as was done by Rous, the organs take on different hues. The diversity of the local media can be visualized. In reality, such diversity is much more profound than is shown by this procedure. But we are not able to detect all its characteristics. In the vast world of the human organism there are most varied countries. Although these countries are irrigated by branches of the same stream, the quality of the water in their lakes and their ponds also depends on the constitution of the soil and the nature of the vegetation. Each organ, each tissue, creates its own medium at the expense of blood plasma. On the reciprocal adjustment of the cells and their medium are based the health or disease, strength or weakness, happiness or misery, of each one of us.
Between the liquids composing the organic medium, and the world of tissues and organs, there are perpetual chemical exchanges. Nutritive activity is a mode of being of the cells, as fundamental as structure and form. As soon as their chemical exchanges, or metabolism, cease, the organs come into equilibrium with their medium and die. Nutrition is synonymous with existence. Living tissues crave oxygen and take it from blood. This means, in physicochemical terms, that they possess a high reducing potential, that a complex system of chemical substances and of ferments enables them to use atmospheric oxygen for energy-producing reactions. From the oxygen, hydrogen, and carbon supplied by sugars and fats, living cells procure the mechanical energy necessary for the maintenance of their structure and for their movements, the electrical energy manifesting itself in every change of the organic conditions, and the heat indispensable to chemical reactions and physiological processes. They also find in blood plasma the nitrogen, sulfur, phosphorus, etc., which they utilize for the construction of new cells, and in the processes of growth and repair. With the help of their ferments they divide the proteins, sugars, and fats contained in their medium into smaller and smaller fragments, and make use of the energy so liberated. They simultaneously build up, by means of energy-absorbing reactions, certain compounds, more complex and having a higher energy potential, and they incorporate them in their own substance.
The intensity of chemical exchanges in the cell communities, or in the entire being, expresses the intensity of organic life. Metabolism is measured by the quantity of oxygen absorbed and that of carbonic acid produced, when the body is in a state of complete repose. This is called basal metabolism. There is a great increase in the activity of the exchanges as soon as muscles contract and perform mechanical work. Metabolism is higher in a child than in an adult, in a mouse than in a dog. Any very large increase in the stature of human beings would, as mentioned heretofore, probably be followed by a decline of basal metabolism. Brain, liver, and endocrine glands need a great deal of chemical energy. But muscular exercise raises the intensity of the exchanges in the most marked manner. Nevertheless, all our activities cannot be expressed in chemical terms. Intellectual work, strange to say, does not increase metabolism. It seems to require no energy, or to consume a quantity of it too small to be detected by our present techniques. It is, indeed, an astonishing fact that human thought, which has transformed the surface of the earth, destroyed and built nations, discovered new universes in the immensity of the sidereal spaces, is elaborated without demanding a measurable amount of energy. The mightiest effort of our intelligence has incomparably less effect on metabolism than the contraction of the biceps when this muscle lifts a weight of a few grams. The ambition of Caesar, the meditation of Newton, the inspiration of Beethoven, the passionate contemplation of Pasteur, did not modify the chemical exchanges of these great men as much as a few bacteria or a slight stimulation of the thyroid gland would easily have done.
Basal metabolism is remarkably constant. The organism maintains the normal activity of its chemical exchanges under the most adverse conditions. Exposure to intense cold does not decrease the rhythm of nutrition. The temperature of the body falls only on the approach of death. On the contrary, bears and raccoons lower their metabolism in winter, and fall into a state of slower life. Certain arthropodous animals, Tardigrade, completely stop their metabolism when they are dried. A condition of latent life is thus induced. After a lapse of several weeks, if one moistens these desiccated animals, they revive, and the rhythm of their life again becomes normal. We have not yet discovered the secret of producing such a suspension of nutrition in domestic animals and in man. It would be an evident advantage in cold countries if a state of latent life could be induced in sheep and cows for the duration of the winter. It might be possible, perhaps, to prolong life, cure certain diseases, and give higher opportunities to exceptionally gifted individuals, if human beings could be made to hibernate from time to time. But we are not capable of decreasing the rate of metabolism, except by the barbarous method that consists of removing the thyroid gland. And even that method is quite insufficient. As far as man is concerned, latent life, for the moment, is an impossible form of existence.
In the course of the chemical exchanges, waste products, or catabolites are set free by tissues and organs. They tend to accumulate in the regional medium and to render it uninhabitable for the cells. The phenomenon of nutrition, therefore, requires the existence of apparatuses capable of assuring, through a rapid circulation of lymph and blood, the replacement of the nutritive substances used by the tissues, and the elimination of waste products. The volume of the circulating fluids, compared with that of the organs, is very small. The weight of blood of a human being is hardly equal to one-tenth of his total weight. However, living tissues consume large amounts of oxygen and glucose. They also liberate into the inner medium considerable quantities of carbonic, lactic, hydrochloric, phosphoric acids, etc. A fragment of living tissue, cultivated in a flask, must be given a volume of liquid equal to two thousand times its own volume, in order not to be poisoned within a few days by its waste products. In addition, it requires a gaseous atmosphere at least ten times larger than its fluid medium. Consequently, a human body reduced to pulp and cultivated in vitro would demand about two hundred thousand liters of nutritive fluid. It is on account of the marvelous perfection of the apparatuses responsible for the circulation of the blood, its wealth of nutritive substances, and the constant elimination of the waste products, that our tissues can live in six or seven liters of fluid, instead of two hundred thousand.
The speed of circulation is sufficiently great to prevent the composition of blood from being modified by the catabolites of tissues. The acidity of plasma increases only after violent exercise. Each organ regulates the volume and the rapidity of its blood flow by means of vasomotor nerves. The interstitial lymph becomes acid as soon as circulation slackens or stops. The more or less injurious effects of such acid poisoning on the viscera depend on the type of their constituent cells. If we remove a dog's kidney, leave it on a table for an hour, and then replant it in the animal, the kidney is not disturbed by the temporary deprivation of blood, but resumes its functions and works indefinitely in a normal manner. Neither does the suspension of the circulation in a limb, for three or four hours, have any ill effects. The brain, however, is much more sensitive to lack of oxygen. When circulation is stopped and anemia complete in this organ for about twenty minutes, death always takes place. After only ten minutes, anemia produces serious and often irreparable disorders. Thus, it is impossible to bring back to normal life an individual whose brain has been completely deprived of circulation for a very short time. Lowering of the blood pressure is also dangerous. Brain and other organs demand a certain tension of the blood. Our conduct and the quality of our thoughts depend, in a large measure, on the state of our circulatory apparatus. All human activities are regulated by the physical and chemical conditions of the inner medium and, ultimately, by the heart and the arteries.
Blood maintains its composition constant by perpetually passing through apparatuses where it is purified and recuperates the nutritive substances removed by the tissues. When venous blood returns from the muscles and the organs, it is full of carbonic acid and waste products of nutrition. The pulsations of the heart then drive it into the immense network of the lung capillaries, where each red corpuscle comes into contact with atmospheric oxygen. This gas, in conformity with certain simple physicochemical laws, penetrates the blood and is taken up by the hemoglobin of the red cells. Carbon dioxide simultaneously escapes into the bronchi, whence it is expelled into the outside atmosphere by the respiratory movements. The more rapid the respiration, the more active are the chemical exchanges between air and blood. But during its passage through the lungs, blood gets rid of carbonic acid only. It still contains nonvolatile acids, and all other waste products of metabolism. Its purification is completed during its passage through the kidneys. The kidneys separate from the blood certain substances that are eliminated in the urine. They also regulate the quantity of salts indispensable to plasma in order that its osmotic tension may remain constant. The functioning of the kidneys and of the lungs is of a prodigious efficiency. It is the intense activity of these viscera that permits the fluid medium required by living tissues to be so limited, and the human body to possess such compactness and agility.
The nutritive material carried by the blood to the tissues derives from three sources. From atmospheric air by the agency of the lungs, from the intestinal surface, and, finally, from the endocrine glands. All substances used by the organism, with the exception of oxygen, are supplied by the intestines, either directly or indirectly. The food is successively treated by the saliva, the gastric juice, and the secretions of pancreas, liver, and intestinal mucosa. Digestive ferments divide the molecules of proteins, carbohydrates, and fats into smaller fragments. These fragments are capable of traversing the mucous membranes, which defend our inner frontier. They are then absorbed by the blood and lymph vessels of the intestinal mucosa, and penetrate the organic medium. Certain fats and sugars are the only substances to enter the body without previously undergoing modification. For this reason the consistency of adipose parts varies in conformity with the nature of the animal or vegetable fats included in the diet. By feeding a dog with fats of a high melting-point or with oils fluid at body temperature, we can render its adipose tissue either hard or soft. Proteins are broken up by digestive ferments into their constituent amino acids. They thus lose their individuality, their racial specificity. In this way, amino acids, and groups of amino acids derived from proteins of beef, mutton, wheat, etc., retain no evidence of their various origins. They build up in the body new proteins, specific for the human race and for the individual. The intestinal wall almost completely protects the organism from invasion by molecules belonging to the tissues of other beings, by opposing the penetration of animal or vegetal proteins into the blood. However, it sometimes allows such proteins to enter. So the body may silently become sensitive, or resistant, to many foreign substances. The barrier raised by the intestines against the outer world is not impassable.
The intestinal mucosa is not always capable of digesting or absorbing certain indispensable elements of the food. In such an instance, even if these substances are present in the intestinal lumen, they cannot enter our tissues. In fact, the chemical elements of the outer world act on each individual in different ways, according to the specific constitution of his intestinal mucosa. From these elements are built our tissues and our humors. Man is literally made from the dust of the earth. For this reason his physiological and mental activities are profoundly influenced by the geological constitution of the country where he lives, by the nature of the animals and plants on which he generally feeds. His structure and his functions depend also on the selection he makes of certain elements among the vegetal and animal foods at his disposal. The chiefs always had a diet quite different from that of their slaves. Those who fought, commanded, and conquered used chiefly meats and fermented drinks, whereas the peaceful, the weak, and the submissive were satisfied with milk, vegetables, fruits, and cereals. Our aptitudes and our destiny come, in some measure, from the nature of the chemical substances that construct our tissues. It seems as though human beings, like animals, could be artificially given certain bodily and mental characteristics if subjected from childhood to appropriate diets.
The third kind of nutritive substances contained in blood, in addition to atmospheric oxygen and to products of intestinal digestion, consists, as already mentioned, of the secretions of the endocrine glands. The organism has the peculiar property of being its own builder, of manufacturing new compounds from the chemical substances of the blood. These compounds serve to feed certain tissues and to stimulate certain functions. This sort of creation of itself by itself is analogous to the training of the will by an effort of the will. Glands, such as the thyroid, the suprarenal, the pancreas, etc., synthetize from the chemicals in solution in the organic medium a number of new compounds, thyroxin, adrenalin, insulin, etc. They are true chemical transformers. In this way, substances indispensable for the nutrition of cells and organs, and for physiological and mental activities, are produced. Such a phenomenon is as strange as if certain parts of a motor should create the oil used by other parts of the machine, the substances accelerating the combustion of the fuel, and even the thoughts of the engineer. Obviously, tissues are unable to feed exclusively on the compounds supplied by the diet after their passage through the intestinal mucosa. These compounds have to be remolded by the glands. To these glands is due the existence of the body with its manifold activities.
Man is, first of all, a nutritive process. He consists of a ceaseless motion of chemical substances. One can compare him to the flame of a candle, or to the fountains playing in the gardens of Versailles. Those beings, made of burning gases or of water, are both permanent and transitory. Their existence depends on a stream of gas or of liquid. Like ourselves, they change according to the quality and the quantity of the substances which animate them. As a large river coming from the external world and returning to it, matter perpetually flows through all the cells of the body. During its passing, it yields to tissues the energy they need, and also the chemicals which build the temporary and fragile structures of our organs and humors. The corporeal substratum of all human activities originates from the inanimate world and, sooner or later, goes back to it. Our organism is made from the same elements as lifeless things. Therefore, we should not be surprised, as some modern physiologists still are, to find at work within our own self the usual laws of physics and of chemistry as they exist in the cosmic world. Since we are parts of the material universe, the absence of those laws is unthinkable.
The sexual glands have other functions than that of impelling man to the gesture which, in primitive life, perpetuated the race. They also intensify all physiological, mental, and spiritual activities. No eunuch has ever become a great philosopher, a great scientist, or even a great criminal. Testicles and ovaries possess functions of overwhelming importance. They generate male or female cells. Simultaneously, they secrete into the blood certain substances, which impress the male or female characteristics on our tissues, humors, and consciousness, and give to all our functions their character of intensity. The testicle engenders audacity, violence, and brutality, the qualities distinguishing the fighting bull from the ox drawing the plow along the furrow. The ovary affects the organism of the woman in an analogous manner. But its action lasts only during a part of her life. At the menopause, the gland atrophies somewhat. The shorter life of the ovaries gives the aging woman great inferiority to man, whose testicles remain active until extreme old age.
The differences existing between man and woman do not come from the particular form of the sexual organs, the presence of the uterus, from gestation, or from the mode of education. They are of a more fundamental nature. They are caused by the very structure of the tissues and by the impregnation of the entire organism with specific chemical substances secreted by the ovary. Ignorance of these fundamental facts has led promoters of feminism to believe that both sexes should have the same education, the same powers, and the same responsibilities. In reality, woman differs profoundly from man. Every one of the cells of her body bears the mark of her sex. The same is true of her organs and, above all, of her nervous system. Physiological laws are as inexorable as those of the sidereal world. They cannot be replaced by human wishes. We are obliged to accept them just as they are. Women should develop their aptitudes in accordance with their own nature, without trying to imitate the males. Their part in the progress of civilization is higher than that of men. They should not abandon their specific functions.
With regard to the propagation of the race, the importance of the two sexes is unequal. Testicle cells unceasingly produce, during the entire course of life, animalcules endowed with very active movements, the spermatozoa. These spermatozoa swim in the mucus covering the vagina and uterus, and meet the ovum at the surface of the uterine mucosa. The ovum results from the slow ripening of the germinal cells of the ovary. In the ovary of a young woman there are about three hundred thousand ova. About four hundred of them reach maturity. Between two menstruations, the cyst containing the ovum bursts. Then, the ovum is projected upon the membrane of the Fallopian tube and is transported by the vibrating cilia of this membrane into the uterus. Its nucleus has already undergone an important change. It has ejected half of its substance--that is, half of each chromosome. A spermatozoon then penetrates its surface. And its chromosomes, which have also lost half of their substance, unite with those of the ovum. A human being is bom. He is composed of a single cell, grafted on the uterine mucosa. This cell separates into two parts, and the development of the embryo begins.
The father and the mother contribute in equal proportions to the formation of the nucleus of the ovum, which engenders every cell of the new organism. But the mother gives also, in addition to half its nuclear substance, all the protoplasm surrounding the nucleus. She thus plays a more important part in the genesis of the embryo than the father does. Indeed, parental characteristics are transmitted to the offspring by the nucleus. But the remaining part of the cell also has some influence. The laws of heredity and the present theories of the geneticists do not entirely elucidate these complex phenomena. When discussing the relative importance of the father and the mother in reproduction, we should never forget the experiments of Bataillon and of Jacques Loeb. From an unfertilized egg, and without the intervention of the male element, a normal frog was obtained through an appropriate technique. The spermatozoon can be replaced by a chemical or physical agent. Only the female element is essential.
Man's part in reproduction is short. That of the woman lasts nine months. During this time the fetus is nourished by chemicals, which filter from the maternal blood through the membranes of the placenta. While the mother supplies her child with the elements from which its tissues are constructed, she receives certain substances secreted by the embryonic organs. Such substances may be beneficial or dangerous. The fetus, in fact, originates almost as much from the father as from the mother. Therefore, a being of partly foreign origin has taken up its abode in the woman's body. The latter is subjected to its influence during the entire pregnancy. In some instances she may be poisoned by her child. Her physiological and psychological conditions are always modified by it. But females, at any rate among mammals, seem only to attain their full development after one or more pregnancies. Women who have no children are not so well balanced and become more nervous than the others. In short, the presence of the fetus, whose tissues greatly differ from hers because they are young and are, in part, those of her husband, acts profoundly on the woman. The importance to her of the generative function has not been sufficiently recognized. Such function is indispensable to her optimum development. It is, therefore, absurd to turn women against maternity. The same intellectual and physical training, and the same ambitions, should not be given to young girls as to boys. Educators should pay very close attention to the organic and mental peculiarities of the male and the female, and to their natural functions. Between the two sexes there are irrevocable differences. And it is imperative to take them into account in constructing the civilized world.
Through his nervous system man records the stimuli impinging upon him from his environment. His organs and muscles supply the appropriate answer. He struggles for existence with his mind still more than with his body. In this ceaseless fight, his heart, lungs, liver, and endocrine glands are as indispensable as his muscles, hands, tools, machines, and weapons. Seemingly for this purpose he possesses two nervous systems. The central, or cerebrospinal system, conscious and voluntary, commands the muscles. The sympathetic system, autonomous and unconscious, controls the organs. The second system depends on the first This double apparatus gives to the complexity of our body the simplicity required for its action on the outside world.
The central system consists of the brain, the cerebellum, and the spinal cord. It acts directly on the nerves of the muscles, and indirectly on those of the organs. It is composed of a soft, whitish, extremely fragile substance, filling the skull and the spinal column. This substance, by the agency of the sensitive nerves, receives the messages emanating from the surface of the body and from the sensory organs. In this way the nervous centers are in constant touch with the cosmic world. Simultaneously, they send their orders to all the muscles through the motor nerves, and to all the organs through the sympathetic system. An immense number of nervous fibers intersect the organism in every direction. Their microscopic endings creep between the cells of the skin, around the acini of the glands and their excretory ducts, in the coat of the arteries and the veins, into the contractile envelopes of the stomach and the intestines, on the surface of the muscular fibers, etc. They spread their delicate network through the whole body. They all originate from cells inhabiting the central nervous system, the double chain of the sympathetic ganglia, and the small ganglia disseminated through the organs.
These cells are the noblest and most elaborate of the epithelial cells. Owing to the techniques of Roman y Cajal, they appear in all their structural beauty. They possess a large body which, in the varieties found on the surface of the brain, resembles a pyramid. And also most complex organs whose functions still remain unknown. They extend in the form of extremely slender filaments, the dendrites, and the axons. Certain axons cover the long distance separating the cerebral surface from the lower part of the cord. Axons, dendrites, and their mother cell constitute a distinct individual, the neuron. The fibrils of one cell never unite with those of another. Their extremities form a cluster of very tiny bulbs, which are in constant motion on their almost invisible stems, as is shown by cinematographic films. They articulate with the corresponding terminals of another cell by means of a membrane, known as the synaptic membrane. In each neuron the nervous influx always diffuses in the same direction in relation to the cellular body. This direction is centripetal for the dendrites, and centrifugal for the axons. It passes from one neuron to the other by crossing the synaptic membrane. Likewise, it penetrates muscular fibers from the bulbs in contact with their surface. But its passage is subject to a strange condition. The value of time, or chronaxy, must be identical in the contiguous neurons, or in the neuron and the muscular fiber. The propagation of nervous influx does not take place between two neurons having different time standards. Thus, a muscle and its nerve must be isochronic. If the chronaxy of the nerve or the muscle be modified by a poison, such as curare or strychnine, the influx no longer reaches the muscle. Paralysis occurs, although the muscle is normal. These temporal relations of nerve and muscle are as indispensable to normal function as is their spatial continuity. We do not yet know what takes place within the nerves during pain or voluntary motion. But we are aware that a variation of electric potential travels along the nerve during its activity. In fact, Adrian has shown, in isolated fibrils, the progress of negative waves, whose arrival in the brain is expressed by a sensation of pain.
Neurons articulate with each other in a system of relays, like electrical relays. They are divided into two groups. One group is composed of receptor and motor neurons, receiving stimuli from the outside world or from the organs, and controlling the voluntary muscles. The other group, of the neurons of association, whose vast number gives to our nervous centers their elaborate complexity. Our intelligence can no more realize the immensity of the brain than the extent of the sidereal universe. The cerebral substance contains more than twelve thousand millions of cells. These cells are connected with one another by fibrils, and each fibril possesses several branches. By means of these fibrils, they associate several trillions of times. And this prodigious crowd of tiny individuals and invisible fibrils, despite its undreamed-of complexity, works as if it were essentially one. To observers accustomed to the simplicity of the molecular and atomic worlds the brain appears as an unintelligible and marvelous phenomenon.
One of the principle functions of the nervous centers is to respond in an appropriate manner to stimuli coming from the environment, or, in other words, to produce reflex reactions. A beheaded frog is suspended with its legs hanging. If one of its toes is pinched, the leg moves, pulling away from the painful stimulus. This phenomenon is due to the presence of a reflex arc--that is, of two neurons, one sensitive and the other motive, articulated with one another within the cord. Generally, a reflex arc is not so simple and includes one or several associating neurons interposed between sensitive and motive neurons. The neuronic systems are responsible for reflexes such as respiration, swallowing, standing upright, walking, as well as for most of the acts of our every-day life. These movements are automatic. But some of them are influenced by consciousness. For example, when we think about our respiratory motion, its rhythm is at once modified. On the contrary, heart, stomach, and intestines are quite independent of our will. However, if we pay too much attention to them, their automatism may be disturbed. Although the muscles that permit standing, walking, and running receive their orders from the spinal cord, they depend for their coordination upon the cerebellum. Like the cord, the cerebellum does not concern itself with mental processes.
The cerebral surface, or cortex of the brain, is a mosaic of distinct nervous organs connected with the different parts of the body. For instance, the lateral part of the brain, known as region of Rolando, controls the movements of prehension and locomotion, and also articulate language. Farther back on the cortex are the visual centers. Wounds, tumors, and hemorrhages located in these different districts result in disturbances of the corresponding functions. Similar disorders appear when the lesions are situated in the fibers uniting the cerebral centers to the lower parts of the spinal cord. The reflexes called by Pavlov conditional reflexes take place in the cerebral cortex. A dog secretes saliva when food is placed in his mouth. This is an innate reflex. But he also secretes saliva when he sees the person who usually brings him his nourishment. This is an acquired, or conditional, reflex. This property of the nervous system of animals and man renders education possible. If the surface of the brain is removed, the building up of new reflexes is quite impossible. Our knowledge of this intricate subject is still rudimentary. We do not know the relations between consciousness and nervous processes, between the mental and the cerebral. Neither do we know how events taking place in the pyramidal cells are influenced by previous or even future events, or how excitations are changed into inhibitions, and vice versa. We understand still less how unpredictable phenomena spring from the brain, how thought is born.
Brain and spinal cord, with nerves and muscles, constitute an indivisible system. Muscles, from a functional point of view, are only a part of the brain. It is with their help and that of the bones that human intelligence has put its mark on the world. Man has been given power over his environment by the shape of his skeleton. The limbs consist of articulated levers, composed of three segments. The upper limb is mounted upon a mobile plate, the shoulder blade, while the osseous girdle, the pelvis, to which the lower limb is jointed, is almost rigid and immobile. The motive muscles lie along the bones. Near the extremity of the arm, these muscles resolve into tendons, which move the fingers and the hand itself. The hand is a masterpiece. Simultaneously, it feels and it acts. It acts as if endowed with sight. Owing to the unique properties of its skin, its tactile nerves, its muscles, and its bones, the hand is capable of manufacturing arms and tools. We never would have acquired our mastery over matter without the aid of our fingers, those five small levers, each composed of three articulated segments, which are mounted upon the metacarpus and the bones of the wrist. The hand adapts itself to the roughest work as well as to the most delicate. It has wielded with equal skill the flint knife of the primitive hunter, the blacksmith's hammer, the woodcutter's ax, the farmer's plow, the sword of the medieval knight, the controls of the modern aviator, the artist's brush, the journalist's pen, the threads of the silk-weaver. It is able to kill and to bless, to steal and to give, to sow grain on the surface of the fields and to throw grenades in the trenches. The elasticity, strength, and adaptiveness of the lower limbs, whose pendulum-like oscillations determine walking and running, have never been equaled by our machines, which only make use of the principle of the wheel. The three levers, articulated on the pelvis, adapt themselves with marvelous suppleness to all postures, efforts, and movements. They carry us on the polished floor of a ballroom and in the chaos of the ice-fields, upon the sidewalks of Park Avenue and on the slopes of the Rocky Mountains. They enable us to walk, to run, to fall, to climb, to swim, to wander all over the earth under all conditions.
There is another organic system composed of cerebral substance, nerves, muscles, and cartilages, which, to the same degree as the hand, has determined the superiority of man over all living beings. It consists of the tongue and the larynx, and their nervous apparatus. Owing to this system, we are capable of expressing our thoughts, of communicating with our fellow men by means of sounds. Were it not for language, civilization would not exist. The use of speech, like that of the hand, has greatly aided the development of the brain. The cerebral parts of the hand, the tongue, and the larynx extend over a large area of the brain surface. At the same time that the nervous centers control writing, speaking, and the grasping and handling of objects, they are, in return, stimulated by these acts. Simultaneously, they are determining and determined. It seems that the work of the mind is helped by the rhythmic contractions of the muscles. Certain exercises appear to stimulate thought. For this reason, perhaps, Aristotle and his disciples were in the habit of walking while discussing the fundamental problems of philosophy and science. No part of the nervous centers seems to act separately. Viscera, muscles, spinal cord, cerebrum, are functionally one. Skeletal muscles, for their coordinated action, depend on brain and spinal cord, and also on many organs. They receive their orders from the central nervous system, and their energy from the heart, the lungs, the endocrine glands, and the blood. To carry out the directions of the brain, they demand the help of the whole body.
The autonomous nervous system enables each viscus to cooperate with the entire organism in our dealings with the outside world. Organs such as the stomach, liver, heart, etc., are not subject to our will. We are incapable of decreasing or increasing the caliber of our arteries, the rhythm of our pulse or of the contractions of our intestines. The automatism of these functions is due to the presence of reflex arcs within the organs. These regional brains are made up of small clusters of nervous cells scattered in the tissues, under the skin, around the blood vessels, etc. There are numerous reflex centers, responsible for the independence of the viscera. For example, an intestinal loop, when removed from the organism and provided with artificial circulation, displays normal movements. A grafted kidney, although its nerves are cut, starts to work at once. Most organs are endowed with a certain freedom. They are thus able to function, even when isolated from the body. However, they are bound by innumerable nervous fibers to the double chain of sympathetic ganglia situated in front of the spinal column, and to other ganglia surrounding the abdominal vessels. These ganglia integrate all the organs and regulate their work. Moreover, through their relations with the spinal cord and the brain they coordinate the activity of the viscera with that of the muscles in the acts which demand an effort of the entire body.
The viscera, although dependent on the central nervous system, are, in some measure, independent of it. It is possible to remove, in a single mass, the lungs, heart, stomach, liver, pancreas, intestines, spleen, kidneys, and bladder, with their blood vessels and nerves, from the body of a cat or a dog, without the heart ceasing to beat, or the blood to circulate. If this visceral entity is placed in a warm bath and oxygen supplied to its lungs, life continues. The heart pulsates, the stomach and the intestines move and digest their food. The viscera can be effectively isolated from the central nervous system in a simpler way, as Cannon has done, by extirpating the double sympathetic chain from living cats. The animals which have undergone this operation continue to live in good health as long as they remain in their cage. But they are not capable of a free existence. In the struggle for life they can no longer call their heart, lungs, and glands to the help of their muscles, claws, and teeth.
The double chain of the sympathetic ganglia is connected with the cerebrospinal system by branches communicating with the cranial, dorsal, and pelvic regions of the nervous substance. The sympathetic or autonomous nerves of the cranial and pelvic regions are called parasympathetic. Those of the dorsal region are the sympathetic. In their action, the para-sympathetic and the sympathetic are antagonistic to one another. Each organ receives its nerves simultaneously from these two systems. The parasympathetic slows the heart, and the sympathetic accelerates it. The latter dilates the pupil, while the former causes its contraction. The movements of the intestines, are, on the contrary, decreased by the sympathetic and increased by the parasympathetic. According to the predominance of the one or the other of these systems, human beings are endowed with different temperaments. The circulation of each organ is regulated by these nerves. The sympathetic brings about constriction of the arteries and pallor of the face, such as are observed in emotion and certain diseases. Its section is followed by redness of the skin and contraction of the pupil. Some glands, such as the hypophysis and the suprarenals, are made up of both glandular and nervous cells. They enter into activity under the influence of the sympathetic. The chemical substances secreted by these cells have the same effect upon blood vessels as the stimulation of the nerve. They increase the power of the sympathetic. Like the sympathetic, adrenalin causes the vessels to contract. In fact, the autonomous nervous system, by means of its sympathetic and parasympathetic fibers, dominates the entire world of the viscera, and unifies their action. We shall describe later how the adaptive functions, those which enable the organism to endure, depend mostly on the sympathetic system.
The autonomous apparatus is linked, as we know, to the central nervous system, supreme coordinator of all organic activities. It is represented by a center situated at the base of the brain. This center determines the manifestation of emotions. Wounds or tumors in this region bring about certain disorders of the affective functions. In fact, it is by the agency of the endocrine glands that our emotions express themselves. Shame, fear, and anger modify the cutaneous circulation. They cause pallor or flushing of the face, contraction or dilatation of the pupils, protrusion of the eye, discharge of adrenalin into the circulation, interruption of the gastric secretions, etc. Our states of consciousness have a marked effect upon the functions of the viscera. Many diseases of the stomach and of the heart originate in nervous troubles. The independence of the sympathetic system from the brain is not sufficient to protect our organs against the disturbances of our mind.
Organs are provided with sensitive nerves. They send frequent messages to the nervous centers and, more particularly, to the center of visceral consciousness. When, in the daily struggle for existence, our attention is attracted by the outside world, the stimuli coming from the organs do not pass the threshold of consciousness. However, they do give a certain color to our thoughts, our emotions, our actions, to all our life, though we do not clearly realize their hidden power. One sometimes experiences, without any reason, a feeling of imminent misfortune. Or an impression of joy, of unexplainable happiness. The state of our organic system obscurely acts on consciousness. A diseased viscus may, in this manner, sound an alarm. When a man, in either good or bad health, feels that he is in danger, that death approaches, such warning probably comes to him from the center of visceral consciousness. And visceral consciousness is rarely mistaken. Of course, in the inhabitants of the new city, sympathetic functions are often as ill balanced as mental activities. The autonomous system seems to become less capable of protecting the heart, stomach, intestines, and glands from the worries of existence. Against the dangers and brutality of primitive life it effectively defended the organs. But it is not strong enough to resist the constant shocks of modern life.
The body thus appears as an extremely complex thing, a stupendous association of different cell races, each race comprising billions of individuals. These individuals live immersed in humors made of chemical substances, which are manufactured by the organs, and of other substances derived from food. From one end of the body to the other, they communicate by chemical messengers--that is, by the agency of their secretions. Moreover, they are united by the nervous system. Their associations, as revealed by scientific techniques, are of an enormous complexity. Nevertheless, these immense crowds of individuals behave like a perfectly integrated being. Our acts are simple. For example, the act of accurately estimating a minute weight, or of selecting a given number of objects, without counting them and without making a mistake. However, such gestures appear to our mind to be composed of a multitude of elements. They require the harmonious functioning of muscular and tactile senses, of the retina, of the eye and hand muscles, of innumerable nervous and muscular cells. Their simplicity is probably real, their complexity, artificial-- that is, created by our techniques of observation. No object seems to be simpler, more homogeneous, than the water of the ocean. But, if we could examine this water through a microscope having a magnifying power of about one million diameters, its simplicity would vanish. The clear drop would become a heterogeneous population of molecules of different dimensions and shapes, moving at various speeds in an inextricable chaos. Thus, the things of our world are simple or complex, according to the techniques that we select for study-ing them. In fact, functional simplicity always corresponds to a complex substratum. This is a primary datum of observation, which must be accepted just as it is.
Our tissues are of great structural heterogeneity. They are composed of many disparate elements. Liver, spleen, heart, kidneys are societies of specific cells. They are individuals definitely limited in space. For anatomists and surgeons, the organic heterogeneity of the body is unquestionable. Nevertheless, it may be more apparent than real. Functions are much less precisely located than organs. The skeleton, for example, is not merely the framework of the body. It also constitutes a part of the circulatory, respiratory, and nutritive systems, since, with the aid of the bone marrow, it manufactures leucocytes and red cells. The liver secretes bile, destroys poisons and microbes, stores glycogen, regulates sugar metabolism in the entire organism, and produces heparin. In a like manner, the pancreas, the suprarenals, the spleen, etc., do not confine themselves to one function. Each viscus possesses multiple activities and takes part in almost all the events of the body. Its structural frontiers are narrower than its functional ones. Its physiological individuality is far more comprehensive than its anatomical individuality. A cell community, by means of its manufactured products, penetrates all other communities. The vast cellular associations called viscera are placed, as we know, under the command of a single nervous center. This center sends its silent orders to every region of the organic world. In this way, heart, blood vessels, lungs, digestive apparatus, and endocrine glands become a functional whole in which all organic individualities blend.
The heterogeneity of the organism is, in fact, created by the fancy of the observer. Should an organ be defined by its histological elements or by the chemical substances it constantly fabricates? The kidneys appear to the anatomist as two distinct glands. From a physiological point of view, however, they are a single being. If one of them is removed, the size of the other at once increases. An organ is not limited by its surface. It reaches as far as the substances it secretes. In reality, its structural and functional condition depends on the rate of elimination of these substances or of their absorption by other organs. Each gland extends, by means of its internal secretions, over the whole organism. Let us suppose the substances set free in the blood by testicles to be blue. The entire body of the male would be blue. The testicles themselves would be more intensely colored. But their specific hue would be diffused in all tissues and organs. Even in the cartilages at the extremity of the bones. The body would then appear to be formed of an immense testicle. The spatial and temporal dimensions of each gland are, in fact, equal to those of the entire organism. An organ consists of its inner medium as much as of its anatomical elements. It is constituted both by specific cells and specific fluid or medium. And this fluid, this inner medium, greatly transcends the anatomical frontier. When the concept of a gland is reduced to that of its fibrous framework, epithelial cells, blood vessels, and nerves, the existence of the living organism becomes incomprehensible. In short, the body is an anatomical heterogeneity and a physiological homogeneity. It acts as if it were simple. But it shows us a complex structure. Such an antithesis is created by our mind. We always delight in picturing man as being constructed like one of our machines.
Indeed, both a machine and our body are organisms. But the organization of our body is not similar to that of the machine. A machine is composed of many parts, originally separate. Once these parts are put together, its manifoldness becomes unity. Like the human individual, it is assembled for a specific purpose. Like him, it is both simple and complex. But it is primarily complex and secondarily simple. On the contrary, man is primarily simple and secondarily complex. He originates from a single cell. This cell divides into two others, which divide in their turn, and such division continues indefinitely. In the course of this process of structural elaboration, the embryo retains the functional simplicity of the egg. The cells seem to remember their original unity, even when they have become the elements of an innumerable multitude. They know spontaneously the functions attributed to them in the organized whole. If we cultivate epithelial cells over a period of several months, quite apart from the animal to which they belong, they arrange themselves in a mosaic, exactly as if to protect a surface. Yet the surface to be protected is lacking.
Leucocytes, living in flasks, industriously devour microbes and red corpuscles, although there is no organism to be defended against the incursions of these enemies. The innate knowledge of the part they must play in the whole is a mode of being of all the elements of the body.
Isolated cells have the singular power of reproducing, without direction or purpose, the edifices characterizing each organ. If a few red corpuscles, impelled by gravity, flow from a drop of blood placed in liquid plasma and form a tiny stream, banks are soon built up. Then, these banks cover themselves with filaments of fibrin, and the stream becomes a pipe, through which the red cells glide just as in a blood vessel. Next, leucocytes come, adhere to the surface of the pipe, and surround it with their undulating membrane. The blood stream now assumes the appearance of a capillary vessel enveloped in a layer of contractile cells. Thus, isolated red and white corpuscles manage to construct a segment of circulatory apparatus, although there is neither heart, circulation, nor tissues to be irrigated. Cells are like bees erecting their geometrical alveoli, synthetizing honey, feeding their embryos, as though each one of them understood mathematics, chemistry, and biology, and unselfishly acted for the interests of the entire community. The spontaneous tendency toward formation of the organs by their constitutive cells, like the social aptitude of the insects, is a primary datum of observation. It cannot be explained in the light of our present concepts.
An organ builds itself by techniques very foreign to the human mind. It is not made of extraneous material, like a house. Neither is it a cellular construction, a mere assemblage of cells. It is, of course, composed of cells, as a house is of bricks. But it is born from a cell, as if the house originated from one brick, a magic brick that would set about manufacturing other bricks. Those bricks, without waiting for the architect's drawings or the coming of the bricklayers, would assemble themselves and form the walls. They would also metamorphose into windowpanes, roofing-slates, coal for heating, and water for the kitchen and the bathroom. An organ develops by means such as those attributed to fairies in the tales told to children in bygone times. It is engendered by cells which, to all appearances, have a knowledge of the future edifice, and synthetize from substances contained in blood plasma the building material and even the workers.
These methods used by the organism do not have the simplicity of ours. They appear strange to us. Our intelligence does not encounter itself in the intraorganic world. It is modeled on the simplicity of the cosmic universe, and not on the complexity of the inner mechanisms of living beings. For the moment, we cannot understand the mode of organization of our body and its nutritive, nervous, and mental activities.
The laws of mechanics, physics, and chemistry are completely applicable to inert matter. Partly, to man. The illusions of the mechanicists of the nineteenth century, the dogmas of Jacques Loeb, the childish physicochemical conceptions of the human being, in which so many physiologists and physicians still believe, have to be definitely abandoned. We must also dismiss the philosophical and humanistic dreams of physicists and astronomers. Following many others, Jeans believes and teaches that God, creator of the sidereal universe, is a mathematician. If that is so, the material world, the living beings, and man have been created, obviously, by different Gods. How naive our speculations! Our knowledge of the human body is, in truth, most rudimentary. It is impossible, for the present, to grasp its constitution. We must, then, be content with the scientific observation of our organic and mental activities. And, without any other guide, march forward into the unknown.
Our body is extremely robust. It adapts itself to all climates, arctic cold as well as tropical heat. It also resists starvation, weather inclemencies, fatigue, hardships, overwork. Man is the hardiest of all animals, and the white races, builders of our civilization, the hardiest of all races. However, our organs are fragile. They are damaged by the slightest shock. They disintegrate as soon as blood circulation stops. Such contrast between the strength and the fragility of the organism is, like most of the antitheses encountered in biology, an illusion of our mind. We always unconsciously compare our body with a machine. The strength of a machine depends on the metal used in its construction, and on the perfection of the assembling of its parts. But that of man is due to other causes. His endurance comes more especially from the elasticity of his tissues, their tenacity, their property of growing instead of wearing out, from the strange power displayed by the organism in meeting a new situation by adaptive changes. Resistance to disease, work, and worries, capacity for effort, and nervous equilibrium are the signs of the superiority of a man. Such qualities characterized the founders of our civilization in the United States as well as in Europe. The great white races owe their success to the perfection of their nervous system--nervous system which, although very delicate and excitable, can, however, be disciplined. To the exceptional qualities of their tissues and consciousness is due the predominance over the rest of the world of the peoples of western Europe, and of their swarms in the United States.
We are ignorant of the nature of this organic robustness, of this nervous and mental superiority. Must they be attributed to the structure of the cells, to the chemical substances they synthetize, to the mode of integration of the organs by the humors and nerves? We do not know. These qualities are hereditary. They have existed in our people for many centuries. But even in the greatest and richest nations they may disappear. The history of past civilizations shows that such a calamity is possible. But it does not explain clearly its genesis. Obviously, the resistance of the body and the mind must be conserved at all costs in a great nation. Mental and nervous strength is infinitely more important than muscular strength. The descendant of a great race, if he has not degenerated, is endowed with natural immunity to fatigue and to fear. He does not think about his health or his security. He is not interested in medicine, and ignores physicians. He does not believe that the Golden Age will arrive when physiological chemists have obtained in a pure state all vitamines and secretory products of endocrine glands. He looks upon himself as destined to fight, to love, to think, and to conquer. He knows that safety should not be first. His action on his environment is as essentially simple as the leap of a wild animal upon its prey. No more than the animal does he feel his structural complexity.
The sound body lives in silence. We do not hear, we do not feel, its working. The rhythms of our existence are expressed by cenesthesic impressions which, like the soft whirring of a sixteen-cylinder motor, fill the depths of our consciousness when we are in silence and meditation. The harmony of organic functions gives a feeling of peace. When an organ begins to deteriorate, this peace may be disturbed. Pain is a signal of distress. Many people, although they are not ill, are not in good health. Perhaps the quality of some of their tissues is defective. The secretions of such gland, or such mucosa, may be insufficient or too abundant. The excitability of their nervous system, exaggerated. Their organic functions, not exactly correlated in space or in time. Or their tissues, not as capable of resisting infections as they should be. Such individuals feel profoundly these organic deficiencies, which bring them much misery. The future discoverer of a method for inducing tissues and organs to develop harmoniously will be a greater benefactor of humanity than Pasteur himself. For he will present man with the most precious of all gifts, with an almost divine offering, the aptitude for happiness.
The weakening of the body has many causes. It is well known that the quality of tissues is lowered by too poor or too rich a diet, by alcoholism, syphilis, consanguineous unions, and also by prosperity and leisure. Wealth is as dangerous as ignorance and poverty. Civilized men degenerate in tropical climates. On the contrary, they thrive in temperate or cold countries. They need a way of life involving constant struggle, mental and muscular effort, physiological and moral discipline, and some privations. Such conditions inure the body to fatigue and to sorrows. They protect it against disease, and especially against nervous diseases. They irresistibly drive humanity to the conquest of the external world.
Disease consists of a functional and structural disorder. Its aspects are as numerous as our organic activities. There are diseases of the stomach, of the heart, of the nervous system, etc. But in illness the body preserves the same unity as in health. It is sick as a whole. No disturbance remains strictly confined to a single organ. Physicians have been led to consider each disease as a specialty by the old anatomical conception of the human being. Only those who know man both in his parts and in his entirety, simultaneously under his anatomical, physiological, and mental aspects, are capable of understanding him when he is sick.
There are two great classes of disease--infectious, or mi-crobian, diseases, and degenerative diseases. The first are caused by viruses or bacteria penetrating into the body. Viruses are invisible beings, extremely small, hardly larger than a molecule of albumin. They live within the cells themselves. They are fond of the nervous substance, and also of the skin and the glands. They destroy those tissues in men and animals or modify their functions. They produce infantile paralysis, grippe, encephalitis lethargica, etc., as also measles, typhus, yellow fever, and perhaps cancer. They can transform inoffensive cells, the leucocytes of the hen, for instance, into ferocious beasts which invade muscles and organs and, in a few days, kill the animal affected with the disease. These formidable beings are unknown to us. Nobody has ever seen them. They only manifest themselves by their effects upon tissues. Before their onslaught, cells stand defenseless. They resist viruses no more than the leaves of a tree resist smoke. In comparison with viruses, bacteria are veritable giants. However, they easily penetrate into our body through the mucosas of the intestines, those of the nose, the eyes, the throat, or through the surface of a wound. They do not install themselves within the cells, but around them. They invade the loose tissues separating the organs. They multiply under the skin, between the muscles, in the abdominal cavity, in the membranes enveloping the brain and the cord. They secrete toxic substances in the interstitial lymph. They may also migrate into the blood. They throw into confusion all organic functions.
Degenerative diseases are often the consequences of bacterial infections, as in certain maladies of the heart and of the kidneys. They are also caused by the presence in the organism of toxic substances issuing from the tissues themselves. When the secretions of the thyroid gland become too abundant, or poisonous, the symptoms of exophthalmic goiter make their appearance. Certain disorders are due to lack of secretions indispensable to nutrition. The deficiency of endocrine glands, of thyroid, pancreas, liver, of gastric mucosa, brings on diseases such as myxedema, diabetes, pernicious anemia, etc. Other disorders are determined by the absence of elements required for the construction and maintenance of tissues, such as vitamines, mineral salts, iodine, metals. When the organs do not receive from the cosmic world through the intestine the building substances which they need, they lose their power of resistance to infection, develop structural lesions, manufacture poisons, etc. There are also diseases which have so far baffled all the scientists and the institutes for medical research of America, Europe, Africa, Asia, and Australia. Among them, cancer and a multitude of nervous and mental affections.
Great gains in health have been achieved since the beginning of this century. Tuberculosis is being vanquished. Deaths from infantile diarrhea, diphtheria, typhoid fever, etc., are being eliminated. All diseases of bacterial origin have decreased in a striking manner. The average length of life--that is, the expectation of life at birth--was only forty-nine years in 1900. Today it has gained more than eleven years. The chances of survival for each age up to maturity have notably augmented. Nevertheless, in spite of the triumphs of medical science, the problem of disease is very far from solved. Modern man is delicate. Eleven hundred thousand persons have to attend the medical needs of 120,000,000 other persons. Every year, among this population of the United States, there are about 100,000,000 illnesses, serious or slight. In the hospitals, 700,000 beds are occupied every day of the year. The care of these patients requires the efforts of 145,000 doctors, 280,000 nurses or student nurses, 60,000 dentists, and 150,000 pharmacists. It also necessitates 7,000 hospitals, 8,000 clinics, and 60,000 pharmacies. The public spends annually $715,000,000 in medicines. Medical care, under all its forms, costs about $3,500,000,000 yearly. Obviously, disease is still a heavy economic burden. Its importance in modem life is incalculable.
Medicine is far from having decreased human sufferings as much as it endeavors to make us believe. Indeed, the number of deaths from infectious diseases has greatly diminished. But we still must die, and we die in a much larger proportion from degenerative diseases. The years of life which we have gained by the suppression of diphtheria, smallpox, typhoid fever, etc., are paid for by the long sufferings and the lingering deaths caused by chronic affections, and especially by cancer, diabetes, and heart disease. In addition, man is liable, as he was in former times, to chronic nephritis, brain tumors, arterial sclerosis, syphilis, cerebral hemorrhages, hypertension, and also to the intellectual, moral, and physiological decay determined by these maladies. He is equally subject to the organic and functional disorders brought in their train by excess of food, insufficient physical exercise, and overwork. The lack of equilibrium and the neuroses of the visceral nervous system bring about many affections of the stomach and the intestines. Heart diseases become more frequent. And also diabetes. The maladies of the central nervous system are innumerable. In the course of his life, every individual suffers from some attack of neurasthenia, of nervous depression, engendered by constant agitation, noise, and worries. Although modem hygiene has made human existence far safer, longer, and more pleasant, diseases have not been mastered. They have simply changed in nature.
This change comes undoubtedly from the elimination of infections. But it may be due also to modifications in the constitution of tissues under the influence of the new modes of life. The organism seems to have become more susceptible to degenerative diseases. It is continually subjected to nervous and mental shocks, to toxic substances manufactured by disturbed organs, to those contained in food and air. It is also affected by the deficiencies of the essential physiological and mental functions. The staple foods may not contain the same nutritive substances as in former times. Mass production has modified the composition of wheat, eggs, milk, fruit, and butter, although these articles have retained their familiar appearance. Chemical fertilizers, by increasing the abundance of the crops without replacing all the exhausted elements of the soil, have indirectly contributed to change the nutritive value of cereal grains and of vegetables. Hens have been compelled, by artificial diet and mode of living, to enter the ranks of mass producers. Has not the quality of their eggs been modified? The same question may be asked about milk, because cows are now confined to the stable all the year round, and are fed on manufactured provender. Hygienists have not paid sufficient attention to the genesis of diseases. Their studies of conditions of life and diet, and of their effects on the physiological and mental state of modern man, are superficial, incomplete, and of too short duration. They have, thus, contributed to the weakening of our body and our soul. And they leave us without protection against the degenerative diseases, the diseases resulting from civilization. We cannot understand the characteristics of these affections before having considered the nature of our mental activities. In disease as in health, body and consciousness, although distinct, are inseparable.
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