Male Sex Glands and Impotence

THE MALE SEX GLANDS

The two testes, which lie enclosed in the scrotal sac of skin just below the penis, secrete semen containing the male reproductive element, the sperm. They also produce the important male sex hormone, testosterone. One of the first known hormones, testosterone's activity was deduced from the events that followed removal of the testes.

 It has been known for centuries that if the testes of a boy are removed or destroyed before puberty, he does not develop typical masculine characteristics. Instead, his personality is gentle, his voice high-pitched, his chest narrow and flat, hismuscles underdeveloped. He lacks facial hair and pubic hair, his penis is small and underdeveloped, and he is impotent. In addition to affecting male sex organs and secondary sexual characteristics, testosterone stimulates muscular and bone development and helps maintain muscle strength. 

If testosterone is injected into a female animal, certain masculine characteristics develop and female hormonal function is inhibited as long as the testosterone injections continue. If testosterone is injected into a eunuch or a man with underactive secretion, the size of the sexual organ increases, secondary sexual characteristics develop, and there is an in- crease in sexual desire and potency.

The effect is transitory. 

People who benefit from testosterone require treatment for their entire lives. It is important to note here that while testosterone administration may be helpful in cases of hormone deficiency; injections of the hormone are ineffective for "rejuvenation" and may in fact be dangerous, sometimes leading to tumor or cancer of the prostate. 

The aging process is not con- fined to sexual function and cannot be halted by a single hormone or any combination of hormones yet discovered. Actually, many men can reproduce at age 70 and beyond. The feeling of decline experienced by some men is more likely to be due to factors other than sex gland inadequacy-either other physical problems or psychological difficulties. A thorough medicalcheckup is advisable rather than costly and potentially dangerous testosterone injections. 

Human nervous system - Central Nervous System

Nerve cells are so specialized that they have lost the ability to repro- duce themselves. When a neuron dies, it cannot be replaced. However, when an axon is damaged, if the damage is at some distance from the cell body, the neuron will not wither away. The damaged section of theaxon may perish but often the remaining section will grow.

 The growth may be slow, although studies in some animals show a growth rate as fast as an inch a week. Even when a neuron is completely destroyed, all is not necessarily lost; sometimes other pathways may' come into use to serve the function of the destroyed unit. " Man's endowment of neurons is vast. For example, the ant, often considered to be a remarkably wise little insect, capable of constructing cunning houses and leading a relatively complex social life, has some 250 neurons.

 Man has billions, and the number can be looked upon as The Brain and Nervous System I 243 an indication of his tremendous potential if he chooses to use them all, and wisely. Actually, man has two nervous systems, not just one.

The Central Nervous System The central nervous system includes the brain and spinal cord. The spinal cord is suspended in a cylinder formed by the bones of the spine. The meninges, which cover the brain, also continue down to serve as protective coverings for the cord. And cerebrospinal fluid, between mid- dle and inner membranes, cushions the cord, just as it does the brain, from shock. 

The central nervous system connects to every part of the body by means of 43 pairs of nerves. Twelve of these, the cranial nerves, go to the eyes and other sense organs, the heart, and other internal organs. They are called olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, auditory, glossopharyngeal, vagus, accessory, and hypoglossal.

The 31 other nervepairs go to skeletal muscles throughout the body. 

They branch off the cord between the bones of the spine. One of a pair goes to the right side of the body, the other to the left. Outside the cord, each nerve splits. One branch carries sensory-type fibers-for incoming messages-to the cord; the other carries motor-type fibers. 

The Brain and Nervous system

The pons, a saddle-like mass of coarse fibers, connects the medulla with the higher brain centers. The medulla, or spinalbulb, just below the pons and at the upper end of the spinal cord, is a switching center for nerve impulses to and from higher brain centers.

 It also contains centers which, as we will see, work through the autonomic nervous system to control heart action, changes in artery walls, breathing, and other activities that go on without our conscious effort. The cerebellum, or little brain, is divided into hemispheres like the cerebrum. The front and back areas control muscle tone. Equilibrium is the concern of an area behind the back lobe. The two main hemispheres coordinate voluntary movements.

It is characteristic of the intricate organization of brain and nervous system that the cerebellum receives nervous messages from the balance mechanism of the inner ears, from the muscles and joints, and from centers deep in the brain, and then sends impulses to the muscles adjusting their tone and coordinating their action. Are you able, with eyes closed, to touch the tip of your nose? Can you both rub your stomach and pat your head simultaneously? Then your cerebellum is still at work.

Protection for the Brain

The brain is an excellent example of built-in protection provided by nature for a vital organ, Despiteprocesses in the brain, brain tissue itself is quite sturdy stuff, tough and resilient. It is protected against injury in a number of ways. A tough bony cage, the skull, surrounds the brain completely. It takes a very strong blow to break the skull. The skull itself is protected by the scalp, which can absorb some tough blows. The scalp is made up of five layers which medical students remember by an acrostic: S is for skin (and hair in which in women constitutes considerable protection), and the skin of the scalp is the thickest in the body; C is for the cutaneous tissue, a layer under the skin; A is for the aponeurosis, a tough layer of fibrous tissue which helps the scalp slide around; L is for some loose tissue;

Still more protection is provided

 Inside the brain are four reservoirs, the ventricles, which contain cerebrospinal fluid. This fluid circulates around the brain. Thus, the brain practically floats on and in fluid. And engineers will tell you that this is an ideal "shock absorber" system. Finally, inside the bone of the skull the brain is wrapped in layers of tissue. One of these layers, the dura mater, is particularly tough and helps protect the brain against blows. But nature cannot provide infinite protection, and it has not foreseen the demands of modern society. It did not anticipate that man would ride motorcycles at 100 miles an hour, and might hurtle over the handle-bars.

Or that children would go out on hard turf and play football. Or those workmen would walk under skyscraper construction projects where a bolt falling from the fortieth floor would develop the speed of anartillery projectile. So we need additional protection: adequate helmets for motorcyclists and athletes, steel hats for workmen exposed to possible head injuries. Parents must realize, too, that babies fall off beds and, at some stage, jump out of cribs. These must be guarded against and a baby doctor can advise. Beyond protecting the brain from injuries, you can protect it so there is no interference with its efficient operation. 

THE FEMALE GENITAL SYSTEM

THE FEMALE GENITAL SYSTEM 

The reproductive anatomy in the female takes the form of the letter "Y." At the ends of the two top arms are the ovaries. The arms themselves are formed by the fallopian tubes, also called oviducts, thin passageways through which eggs released from the ovaries travel. At the Y's center is the uterus, or womb, the muscular pear-sized organ which will house and nourish a fertilized egg from earliest stages through all phases of fetal development, enlarging greatly in the process.

The cervix is the neck of the uterus, which seals off the uterine cavity until, in the last hours prior to birth of a baby, it changes its shape. The cervix leads into the vagina, the receiver of sperm during intercourse and the exit passage for the baby at birth. Elsewhere in this book, as the Index indicates, are discussions of menstruation, menopause, pregnancy, childbirth, and sterility. Hygiene Douches are not essential to feminine hygiene, although many women have been persuaded to take frequent douches with commercial preparations because of advertisements implying that no woman can be clean or dainty without them.

Actually, nature has provided for the cleansing of the internal passages. If you wish to take an occasional douche, it should be of the mildest type, imitating nature's own secretions. You can use a physiological salt solution: add two level teaspoonful of table salt to a quart of moderately warm water.

Administer the douche under gentle pressure. Whether a woman, during the menstrual period, should use an internal absorptive pad (tampon) or an external sanitary pad is entirely a matter of personal preference.

 Either is safe. Each woman can decide for herself, based upon which she finds more effective and comfortable. An unmarried woman can wear an internal pad if her hymen happens to be well perforated-and this may be the case, contrary to some opinion, whether or not she has ever had sexual relations. 

Certain kinds of exercise may cause rupture of the hymen in a virgin. If the hymen is completely lacking in perforation-a condition called imperforate hymen-there may be interference with menstruation, and a minor surgical procedure may be needed to create an opening. Any irregularity in menstruation, once menstruation has become well established, should be checked with your physician. Infections Syphilis, gonorrhea, and non-venereal infections can seriously damage the female reproductive system. 

Examine the stomach with an instrument called the gastro scope

 Examine the stomach with an instrument called the gastro scope

Such tests, and others that sometimes may be needed, are well worthwhile. Almost every disturbance of the gastrointestinal tract that makes itself known by indigestion can be helped if identified in time. It is reassuring to know that tumors are rather rare causes of the tremendous number of cases of chronic indigestion. On the other hand, a disease can progress to a serious, even fatal stage while you are engaged in "treating" your indigestion-for example, if you take a cathartic for indigestion which is caused by appendicitis. 

Let your physician decide whether or not you should take any medicine. Realistically, we know that few people will consult a physician for every mild stomach upset.

If it is, indeed, only a mild upset, we recommend one of the following remedies: a level teaspoonful of bicarbonate of soda in water or, if you prefer, in fruit juice; or 10 to 20 drops of essence of peppermint taken either on a lump of sugar or in a teaspoonful of sugar, and chewed slowly; or a teaspoonful or two of iced creme de men the, or other liqueur or brandy, sipped slowly; or a little wine such as sherry. 

For nausea or cramping, tincture of belladonna is helpful. Adults require 15 to 20 drops in water. Each person must find his proper dosage. Usually, an effective amount will cause some dryness of the mouth or slight blurring of vision. The dosage can be repeated in four to six hours. For more intense abdominal cramps, one to two teaspoonsful of paregoric may be used (see Appendicitis, page 531). 

Lomotil, two tablets four times a day, is prescribed by many physicians for tourist cramps and other gastrointestinal complaints. A persistent "nervous" stomach may be helped by mild sedatives such as phenobarbital, especially if given in combination with tincture of belladonna. However, this medication should be prescribed only by a physician. Aspirin, taken for headache, cold, or rheumatism, sometimes produces stomach distress. 

Stomach and health problems- Digestive system

The one problem:

The stomach wound refused to heal completely. St. Martin refused any kind of operation that might close the stomach wall, preferring instead to get along with bandages in place of an intact wall. He did get along remarkably well, and cooperated with Beaumont, who decided to take advantage of the unfortunate situation to make some observations. It was this work that led to the isolation of hydro- chloric acid in the stomach. And from it came many other findings. Beaumont was able to note, for example, that the stomach became flushed with blood when St. Martin became angry and that it also moved about with considerable energy during anger.

Organic diseases-including ulcer, cancer, virus infection, food poisoning, and many otherscan, of course, affect the digestive system. You can protect the digestive system by taking many simple, sensible pre- cautions. For one thing, you can be sensible about the food you eat. If you know that some particular food does not agree with you, you should avoid it. If you happen to be a person with a sensitive colon, it may be that raw vegetables or fresh fruits trouble you. Some people are bothered unduly by such gas-forming foods as radishes, cabbage, cucumbers, and eggs. 

Alcoholic beverages may cause great difficulties for some sensitive people, leading to diarrhea or cramps in some and belching in others. Excessive smoking can upset the stomach.

The list of possible trouble- makers is long; individual sensitivities vary greatly. You need to, and can, be your own "alimentary tract detective." You should, of course, eat a balanced diet. Since such a diet will contain well-proportioned amounts of proteins, carbohydrates, and fats, without an excess of any, it will put less of a strain on anyone particular digestive function. 

Avoid rapid eating; the stomach works overtime in trying to handle a meal you did not take time to eat properly-and it may start sending out distress signals. None of us can be entirely free of tension. We're all subject on occasion to "nerves." But we can see to it that we make mealtime a reason- ably pleasant, relaxed time, as an aid to both enjoyment of food and its better digestion. 

APPENDIX

APPENDIX 

The appendix is a wormlike appendage at the junction of small and large intestines. Its reason for existence is not clear. The apparently useless structure, unfortunately, can be the source of serious illness. No age group is immune to appendicitis, an inflammation of the appendix (page 531). Its prompt diagnosis can lead to effective removal of the inflamed organ before serious complications can occur. 

The operation is comparatively simple and safe when performed early by a competent surgeon. The one thing you can do about your appendix is to realize that if it is inflamed, you may cause it to rupture if you take a laxative or apply a hot water bottle over it.

CARE OF THE DIGESTIVE SYSTEM 

Unlike the chest with its rib cage, the abdomen offers relatively little protection for its organs. Liver, spleen, and kidneys may be ruptured by accidental injuries. The abdominal muscles should be kept strong to help protect adjacent organs, a need recognized by all coaches of athletic teams. Disorders of the gastrointestinal system are among the most commonly encountered in medical practice. 

Almost everyone has some degree of difficulty at one time or other. The disorders can be functional. Because of the extensive nerve connections involved in the digestive system, fear, anger, and other nervous upsets can readily set off attacks of nausea, cramps, diarrhea, and other symptoms. 

Throat infections and nasal problems

 Fortunately, they do not attack when body resistance is high. When, however, resistance is lowered-by fatigue, poor nutrition, emotional turmoil, or another infection -a lung infection can strike suddenly. The most common lung infections are pneumonia and tuberculosis. 

Today, they can be treated effectively with medications chosen to combat the involved organisms. But much can be done to prevent their development through following the rules of good nutrition, reasonable everyday living with a balance of work, rest, and relaxation, and by paying attention to prompt and proper treatment of minor infections. 

If you are a worker in any industry where dust, gases, and smoke are inhaled, you should recognize the possibility of harm. By all means, check to determine whether increasingly stringent health laws aimed at minimizing or eliminating risk are being followed to the letter by your employer. If they are not being followed, it is a matter that should be brought to the employer's attention and, if necessary, to the attention of health authorities.

 If they are being followed and yet some risk remains, if you even suspect that you may be suffering some ill consequences, it is imperative to see your physician. It may be necessary, particularly if you happen to be especially sensitive to any specific materials, to change your job if your health is to be protected. We would like to emphasize here, too, that the moisture content (humidity) of air can influence health. 

There is considerable individual variation. Some people feel well in cold weather areas where the indoor air is extremely dry because of heating. Other people notice that this dry atmosphere irritates nose and throat. They react very much better when using humidifying devices now available commercially in many forms. 

Respiratory System - Causes and problems

THE RESPIRATORY SYSTEM

 MAN CAN survive for weeks without food, for days without water, but for only a few minutes without air. Air must reach the lungs almost constantly so that oxygen may be extracted there and distributed via the blood to every body cell. Even in a relaxed state, you breathe in and out 10 to 14 times a minute, with each breath lasting 4 to 6 seconds. In the space of a minute, you take in 9 to 12 pints of air. The fact is that the body has small reserves of oxygen, all of it consumed within less than half a minute after the start of vigorous exertion. And with such exertion, the need for air increases many fold so that yours breathing rate may speed up to one second per breath and a total intake of 20 gallons of air a minute. 

You can figure roughly that in a normal day you will breathe in some 3,300 gallons of air-enough to occupy a space about 8 feet by 8 feet by 8 feet-and, in a lifetime, you will consume a prodigious quantity, enough to occupy 13 million cubic feet of space. The respiratory system is one, of course, that you will want to under- stand well. It is a system in particular that you can do much to guard through knowledge of how it functions, what can go wrong, and the preventive techniques available for you to use.

THE NOSE

Respiration begins with the nose, which is specially designed for the purpose, although there will be times when you breathe through the mouth as well. As you read this, you are quietly, with little or no awareness, breathing lightly through your nose. When you race for a bus or train, or perform any vigorous activity, and begin to puff and pant, you are breathing rapidly through the mouth to provide the blood with the extra oxygen needed. The mouth, however, is not designed for breathing. You may have noticed this on cold days when you make a deliberate effort to keep your mouth tightly closed, because if you take air in through the mouth you can feel its coldness.

Cold air passing through the mouth has no chance to become properly warmed. But cold as the air may be, you can breathe comfortably through the nose. The nose, acting somewhat like an air conditioning system, regulates the temperature and humidity of air passing through and filters out foreign particles as well. Air enters, of course, through the nostrils. Hairs around the nostril openings catch dust and other impurities. The nostrils are separated by a partition, the septum, which is made of cartilage-a flexible kind of bone -in the lower part of the nose, and of real bone in the upper part. Thus, while you can pull the bottom part of the nose from side to side, the top part is immovable. 

Heart and Blood circulatory system protective care

 PROTECTIVE CARE There is much you can do to guard the health of your heart and circulatory system. Contrary to what many people believe, the heart is a tough rather than delicate organ. Surgeons have successfully closed stab and other wounds of the heart; they have repaired the valves within the heart and corrected malformations. Protected by the tough ribs, the over- lying lungs, and its own surrounding membrane, the heart is rarely dam- aged by a blow. This fact should be reassuring to parents of football players, boxers, and other athletes. Guarding the health of the heart does not mean trying unduly to spare it.

Heart that a practice now accepted as a safeguard-a gradual return, after an actual heart attack, to active, even strenuous exercise-would, only a decade ago, have been considered medical malpractice if a doctor had prescribed it. Today, many cardiologists advise patients after heart attacks to get moving-to begin slowly, with extreme caution, gradually increasing their activity. With a gradual, well-tailored, well-supervised program, there is little or no danger of overstraining the heart. Many ex-heart cripples now are even playing strenuous games such as handball. It is now realized that such slow, gradual, progressive physical training can help the heart develop an increased network of blood-supplying vessels, sometimes a greater network than it may have had before the heart attack, and there is increasing evidence that such training may substantially reduce the risk of another attack. However, there are limits to the amount of strain that should be placed on a middle-aged, old, or damaged heart, particularly sudden strain. If you have been leading a sedentary existence, and now, wisely, you decide you need to increase your physical activity and overall physical fitness, you should by all means check with your physician first and, with his guidance, based on the health of your heart and whole circulatory system, map out a program which will lead gradually to your goal. 

Blood How it works on body care?

BLOOD

Blood, the body's transport medium, consists of about equal parts of a watery fluid called plasma and a mixture of red cells, white cells, and platelets. The red cells give blood its color and there are some 25 trillion of them. Each lasts about four months, wearing out and breaking up. And new cells to replace the old are produced in the bone marrow at a rate of about one million a second. The red color of the cells comes from hemoglobin, a combination of protein and an iron pigment. It is the hemoglobin that actually carries oxygen from the lungs to the capillaries and then carries carbon dioxide to the lungs, where it is exhaled.

Hemoglobin is a substance with an ability to hold very large quantities of oxygen. If it didn't exist, and if oxygen had to be dissolved in blood plasma, the body would require 300 quarts of blood instead of 5. White cells are less numerous than red but still there are 20 to 50 billion of them. Typically, in a pinprick of blood there may be some 10,000 white cells and as many as 5 million red cells. There are several kinds of white cells. One type, the granular leukocyte, is produced in the bone marrow along with red cells. Another, the lymphocyte, is produced in the lymph nodes, tonsils, and adenoids. White cells have an important role in the body's defense against invasive bacteria. Unlike the red cells, the white ones can move. They usually move along the sides of blood vessels rather than being pushed along with the red cells in the middle. They move by pushing out part of themselves ahead, then sliding the rest into the advanced area.

They can flow around and engulf bacteria. The battle, however, is not all one-sided. White cells can be destroyed by bacterial poisons, and pus is an accumulation of dead white cells and bacteria. But while bacteria sometimes can overwhelm the white cells, much more often the outcome is the other way, and most bacterial invasions (and they occur almost constantly) are repulsed. The blood platelets, which are smaller than the red cells, help blood to coagulate or clot. They collect at the site where a blood vessel is cut or otherwise injured, and they produce tiny fibrin threads, which lead to clot formation, helping to minimize blood loss. Plasma, which constitutes about half of whole blood, and is the part without cells, is itself about 91 percent water.

The remainder is made up of such minerals as sodium, calcium, potassium, and phosphorus, plus fats, sugars, plasma proteins, and antibodies. Antibodies are another part of the body's defense mechanism. Micro- organisms entering the body stimulate the production of antibodies which then, in very specific fashion, lock on to and incapacitate them. And it is by causing the body to produce antibodies specific against a particular disease organism that vaccines work. After use of a vaccine, the antibodies are in the plasma, ready and waiting to attack immediately if the disease organism should appear.

Heart and blood circualtory system

 THE HEART'S OWN SUPPLY The heart, being a muscle, and a hard-working one, needs nutritious blood. And nature has seen to it that it gets it by special means. The heart's special system begins at the aorta, from which branch off two arteries, the coronaries, each about the size of a thick knitting needle. One enters the heart muscle on the right side; the other, on the left. And the two together form a kind of wreath about the heart. The coronaries divide and divide to feed every part of the heart muscle. And after the blood has deposited its oxygen supply and picked up waste, it is carried by a system of veins to the right atrium to be passed, along with blood returning from other parts of the body, to the lungs. As we have noted, the heart has remarkable ability to adapt to demands of the body-to beat faster, contract more completely, and thus pump much more blood when necessary.

 In turn, the coronary circulation has remarkable ability to adapt to the heart's needs when they increase. When the heart must work harder, it needs more nourishment -and the coronary circulation accommodates. Ordinarily, the coronary arteries take only a small fraction of the blood moving through the aorta. But when the heart is working harder, the arteries will take more, even up to half of the total flow through the aorta. An unusual feature of the coronary circulation is the presence of extra capillaries, many of which form connections between the two coronary arteries. These extra tiny vessels lie unused and empty except when you are exerting yourself to the point of putting bigger demands on the heart. Then they go to work to bring more blood and oxygen to the heart muscle. These same capillaries help, too, if some of the regular blood channels no longer function effectively because of disease. Then the spare capillaries go into regular use as substitute pathways. There is another safeguard in the fact that each coronary artery doesn't supply only its own side of the heart.

Branches extend over to the other side so that many heart areas have blood supplied from both coronary arteries. Thus, if one of these vital vessels should become dis- eased and narrowed, all is not necessarily lost.

Pulse blood system blood distribution blood pressure

THE PULSE You have undoubtedly noted physicians-and perhaps you have done the same yourself-place a finger on the radial artery ,It the wrist to "take" the pulse. The pulse is caused by the impart of blood on the arteries as the heart beats. It provides useful information about the strength and regularity of blood flow. Generally, for a person in good health, the pulse may speed up from around 70 a minute to more than 120 after vigorous exercise, but then, within three minutes, should return to the original value. There may be some quite normal deviations from average beat, deviations too from the beat with vigorous exercise, and deviations from the average interval required for return to the pre-exercise rate. If you have any doubt in your own case, you should check with your physician.

BLOOD PRESSURE Blood pressure is the force exerted against the walls of arteries as blood flows through. With each contraction of the ventricles, which is called a systole, there is a spurt of blood and this increases blood pressure. During the art of the cycle when the ventricles are not contracting, called the diastole, the pressure decreases. Thus, there is always pressure of blood, highest during systole and called the systolic pressure, lowest during diastole and called diastolic pressure. These pressures can be readily measured with an instrument, the sphygmomanometer (see page 24). And, as the discussion under high blood pressure indicates (page 596), measurement of pressure is an important means of determining the health of the heart and circulatory system.

BLOOD DISTRIBUTION The circulation of blood-so often dismissed as "blood from the heart into the arteries, to the tissues, then back to the heart through the veins" -is, in the human body, a really intricate and marvelous process. For it is remarkably adaptable. When blood moves from the heart into the aorta, it is at a speed of about 15 inches a second. Almost immediately, distribution around the body begins through arteries branching off from the aorta. From the smallest arteries, even smaller vessels called arterioles branch out. From the arterioles, blood flows to the smallest of all vessels, the capillaries. The capillaries transport blood to individual cells; and through microscopic spaces in the capillary walls, oxygen and other supplies are diffused to the cells and, in return, waste materials move into the blood- stream. The capillaries connect with venules, tiny vessels of the venous return system, which run into veins. The veins carry the blood to the great venae cavae, large vessels which empty into the right atrium of the heart.  

Heart Problem heart foundation heart beat

 The atrium and ventricle on the right are separated from their counterparts on the left by a wall of muscle, called a septum. Into the right atrium comes "used" blood returning from coursing through the body, during which trip it has given up its oxygen to body cells in exchange for cell wastes. It now needs freshening and it flows from the atrium through a valve into the right ventricle. The valve, the tricuspid, is there to prevent blood from being pushed back into the atrium when the ventricle contracts. The contraction of the ventricle pushes the bluish "used" blood into the pulmonary artery toward the lungs. 

Thus the right side of the heart is a pump devoted to moving blood toward the lungs for oxygenation. When the blood, freshened in the lungs, returns through the pulmonary veins to the heart it enters the left atrium. From here it goes, through the mitral valve, to the left ventricle. And it is the contraction of the left ventricle that sends a surge of fresh blood into the aorta, the great artery which comes out of the heart and from which branches run to all parts of the body. Valves to prevent backward flow of blood are also located where the aorta and pulmonary artery emerge from the heart.

 THE HEARTBEAT 

The beat of the heart-on the average, 72 times a minute--starts in a knot of tissue called the sinoatrial node located in the atria. The node contains nerve cells and fibers and muscle cells and is called the heart's pacemaker because it gives rise to the impulse, or spark that starts a wave of contraction. The wave spreads over the muscle of the atria and, upon reaching another node near the junction of atria and ventricles, produces an impulse which leads to contraction of the ventricles. 

As already noted, the heart does not lie entirely on the left side, de- spite a popular notion to that effect. Rather it is near the midline with about one third of its bulk on the right and two thirds on the left. The flatter base of the heart faces backward, and the sharper apex faces out and downward. It is the apex that reaches to the left, and because it pulses with each beat; the heart appears to be centered at that spot rather than stretching toward it. 

Blood and circulatory system

 THE CIRCULATORY SYSTEM \ ALL LIVING cells of the body must have a supply of fuel, water, and oxy- gen brought to them and must have their waste products removed. This is the function of the remarkable circulatory system, consisting of the heart and a vast network of blood vessels. In recent years, much knowledge has been acquired about the functioning of the human heart and circulatory system and about factors critical for the health and welfare of the system. There have been significant developments in the area of prevention of disturbances, and there are many measures which you can take quite readily.

THE HEART weighing less than a pound when full grown and only a little larger than your fist, the human heart ranks as perhaps the world's most fantastic machine. Despite its small size, it beats an average of 72 times a minute, 100,000 times a day, nearly 40 million times a year. Each day it pumps the equivalent of some 5,500 quarts of blood weighing 6 tons through more than 60,000 miles of the circulatory system. The work done by the heart is comparable to the effort you would have to expend to lift a ten- pound weight three feet off the ground twice a minute for the whole of your life. A hollow organ, the heart perches in the front part of the chest, under the breastbone in the center, with its apex pointed to the left. It has a muscular wall, the myocardium, which is surrounded by a fiber like bag, the' pericardium, and is lined by a strong, thin membrane, the endo  heart is actually ,I double pump,  our chambers two at the top called atria and two at the bottom called ventricles.

Major Muscles and muslce power

Since muscle fibers exert pull when they contract, they use energy. The energy comes from food supplied to them through the blood. A muscle works by converting chemical energy into mechanical energy. Actually, only about one fourth of the chemical energy is converted properly into mechanical energy; the remaining three fourths is lost as heat, raising the temperature of anyone doing strenuous work. This efficiency of 25 percent is similar to that of an automobile engine, which also loses much of its energy as heat. There have been calculations which suggest that the maximum energy output for man is about 6 horsepower and that as much as 0.5 horse- power output can be sustained almost indefinitely.

SOME MAJOR MUSCLES Skeletal muscles are of many shapes and sizes suited to their particular jobs-and they have many jobs. The sternomastoid muscles, which are on either side of the head, serve two purposes. When you nod your head, it is because both of the sternomastoid muscles contract simultaneously. You turn your head to one side or the other depending upon which of the two you contract. Among muscles at the shoulder are the trapezius, which shrugs the shoulder when it contracts, and the pectoralis major, which spreads over the chest and attaches to the humerus and helps sweep the arm across the chest. On the forearm are muscles that divide into tendons extending down to the fingertips; they help move the fingers.

 Among the big muscles of the lower extremity are the gluteal muscles on the buttocks, which, with their contraction, move you from sitting to standing position and are involved in walking; the sartorius, in the thigh, the longest muscle in the body, which pulls the thigh into cross-legged position; the quadriceps in the thigh used [or balance during standing and for kicking; and the gastrocnemius and solt'us in the calf which enable you to stand on tiptoe and provide from the ground for walking, running, dancing. Along each side of the spinal column maintain an erect posture, to bend the body, and to help turn it to one side or the other. Inside the body is the major muscle for breathing, the diaphragm, which is attached through tendons to the spinal column, ribs, and lower tip of the breastbone. The contraction of the diaphragm helps fill the lungs with air. And the diaphragm, incidentally, is also used in laughing, sneezing, and coughing. Its spasmodic contractions occasionally produce hiccupping. 

Bone joints, ligaments and Bursas

JOINTS, LIGAMENTS, AND BURSAS Joints and ligaments connect bones to each other. At the ends of bones are smooth, gliding joint surfaces which make possible easy, painless movement. A joint consists of a fibrous sheath attached to the smooth ends of the bones. Nature also provides, for the ends of those bones that take part in body movements, a special material, cartilage, which has a resiliency and smoothness that enable fingers, arms, and legs to move many thousands of times daily without making us conscious of their activities. To bind bones together and strengthen the joints, there is a special type of tough "binding cord" called tendon. Tendons are so firmly attached to the bones that only an exceptional strain will tear them away.

A final element in the smooth, effective movement of joints is the bursa. This is a sac or bag with smooth surfaces which contains a small amount of lubricating material. Everyday care of the joints, ligaments and bursas is important. An injured joint, torn ligament, or inflamed bursa-as anyone who has ever suffered one knows-can interfere seriously with enjoyment of life and may ~en be incapacitating. It's essential that you work with, not against, nature so you impose no extra stress on joints, ligaments, and bursas. For one thing, that means maintenance of normal weight; gross over- weight overloads the joints of knees and feet every time you stand or walk.

Good posture also is important for keeping joints in good condition, distributing weight as nature engineered the body to handle it. And good physical condition, which helps to assure good muscle tone, helps to avoid undue strain. We suggest that, in connection with proper care of joints, ligaments, and bursas, you read sections of this book dealing with posture and exercise (page 80) and weight reduction (page 59) if you are over- weight. Everyone should know the proper technique for lifting objects -by bending the knees and bringing into play the leg muscles to help with the lifting rather than relying entirely upon the muscles of the back.

There are many injuries and diseases that can affect the bones, joints, ligaments, and bursas. These are discussed later in this book-e.g., arthritis and rheumatism, fractures, backaches, bursitis, bone diseases. 

How Human recovering with its own strengths - How to save the capacity?

During World War II, a marine lieutenant on Okinawa received four shell fragments that ripped through the whole left side of his brain, leaving him paralyzed on one side of his body, unable to read, write, talk, or even understand what was said to him. Two years later, he was in college, his paralysis largely overcome, and his ability to read, write, and talk restored. If necessary, the stomach can be removed completely-and has been to save the lives of cancer patients-with part of the large intestine transposed to become a kind of new stomach.

Eighty percent or more of the small intestine-the organ that normally does most of the work of digesting food-can be dispensed with. More than three quarters of the liver can be removed. One kidney, if necessary, can support life. So can one lung. Virtually every organ can be removed from the pelvic area, and life can go on. In fact, a super-radical operation has prolonged life in otherwise hopeless cases when cancer of the vulva, uterus, ovaries, vagina, bladder, or rectum has spread to adjacent organs. The operation involves removal of all organs, nerves, and blood vessels in the pelvic region; nothing is left there. The body has been known to survive extremes of hunger, thirst, temperature.

A South Barre, Massachusetts, seaman lived after floating on a raft at sea for 83 days without food and, during the last 12 days, without water. At Memorial Hospital, New York, a 100-pound woman survived a fever of 114 degrees, possibly the highest on record. At the other extreme, a young Chicago woman survived a body temperature of 60.8 degrees. On a November day some years ago, a young woman in Newcastle, England, gave birth to a child. The previous May she had been struck on the head by a log falling from a truck and had lost consciousness. She had remained unconscious for 169 days. For seven days, too, she had been in a state approaching hibernation when, as part of treatment, cooling had brought her temperature down to well below normal. 

She recovered in time to give birth without complications to a husky 8-pound son. But capable as the body is of demonstrating remarkable powers in emergencies, it is obviously the better part of wisdom to avoid the need. The purpose of this section is to consider the various systems of the body, to provide what we hope will be practical, useful insights into how they are organized and their functioning, how nature has provided for their protection, and what you can do to add to the protection. Total health represents the summation of the health and efficient functioning of the individual parts of the body. If lungs, heart, liver, kidneys, skin, and other organs and tissues work at maximum efficiency-and if, to this, is added a healthy mind free of excess nervous tension, anxiety, or depression-then the basis for full enjoyment of the body and of life is complete. The complex and wonderful human mind will be covered in the next section. The body, as you will see in this section, is no less complex and wonderful. 

Job related Health problems -stress-frustration-mental health

If your job brings you sufficient income but leaves you frustrated, bored, or otherwise unhappy, vocational guidance agencies may help solve the problem. 

It could be worthwhile, too, for you to have a frank talk with your physician who, knowing the importance of job satisfaction as a factor in good preventive medicine, may himself be able to help with some guidance or refer you to a psychologist or psychiatrist for help in discovering whether you should try to adjust yourself to your present job-whether there are things you can do to make a satisfying adjustment or find another.

A good job, too, should be as safe as modern technology and your own alertness, ingenuity, and awareness of potential hazards can make it. 

If you are frequently ill or have had accidents at work, it may be that you do not observe proper precautions, or it may be the result of poor conditions in your place of employment. After reading this chapter, you may be able to decide better which it is. If it is the latter-poor work conditions you can bring the fact to the attention of your employers, either directly (perhaps through a suggestion box) or through your foreman, supervisor, or union.

If this fails to produce improvement, the matter should be reported to the proper authorities, such as the department of labor in your state or the local or state health department. The fact is that while much has been done to improve occup.ulon.il safety in this country, in any year on-the-job accidents kill 10, 00,000 partially or completely disable 2,200,000 of the nation's 12 million workers. Another 5 million suffer lesser work injuries toll in pain and suffering, job-related accidents ,  $1.5 billion in lost wages and deprive industry of  $millions. This record is an improvement over residents killed nearly twice as many people in a work force half the size of todays, but it leaves much to be desired. 

Smoking studies and research on lung cancer and cardio problems

A United States study found death rates for men aged 45 to 64 to be 6.6 times as high for smokers; in the age group 65 to 84, 11.4 times as high. For women smokers, it is, overall, 4.9 times as high as for nonsmokers and 7.4 times as high for the heavier smokers.

Smoking: American heart Association authorities stated that 100,000 preventable deaths each year are associated with cigarette  as published by the National Cancer Institute, "Smoking in the Death Rates of One Million Men and Women," the conclusions were reached: In the 45 to 54 year age group, deaths from coronary heart disease are 2.8 times as high for men as high for women smoking a pack or more of cigarettes or nonsmokers. 

The greater the number of cigarettes smoked, the inhalation, and the earlier the age when smoking starts, better the death rate. And autopsies of people dying from diseases him coronary heart disease show more plaques, or roughened, on which clots can develop and much more extensive atherosele - the coronary arteries of smokers than nonsmokers.

Many studies show that smokers have larger amounts of cholesterol in the blood than nonsmokers. Other studies indicate that smoking prevent clotting of blood, which increases risk of clot formation in the coronary arteries. Smoking also increases the work load of the heart, forcing it to pump more blood more rapidly because the carbon monoxide from smoke reduces the oxygen-carrying capacity of the blood and impairs the elasticity and gas-exchange capacity of the lungs. 

There is evidence, too, of an association between cigarette smoking and strokes, which annually kill 200,000 Americans. An American Cancer society study found that stroke death rates are 74 percent higher among women and 38 percent higher among men who smoke cigarettes than among nonsmokers.