Some industrial processes produce dusts. These processes include drilling, polishing, crushing and sawing. Industrial dusts are often much smaller than the ordinary dust in the air. This means that they can avoid being trapped by the mucus in the air passages. Therefore these dusts can get into the lungs. This can cause serious diseases such as silicosis or pneumoconiosis of coal miners. It is because of diseases such as these that there are strict regulations about the conditions under which men and women work in industry. These regulations are being brought up to date all the time as our knowledge of industrial diseases grows.
Lung cancer kills more men today than any other type of cancer. The disease starts quietly and you may feel nothing at first. Often, by the time lung cancer is discovered, it is too late to treat it. People with this disease may suffer great pain before it finally kills them. Lung cancer is much more common in smokers than in non-smokers.
In this disease, cells in the lungs or in the air passages suddenly stop behaving normally. Instead they start to multiply rapidly. They form a lump or tumour. Doctors call this a carcinoma. The lump grows slowly at first and gradually blocks some of the air passages. It slowly invades the healthy parts of the lungs. One of the most dangerous things about lung cancer is that it starts quietly and secretly. The victim often feels nothing at first. Later a cough may start. Then breathing becomes more difficult. The cancerous lump is often widespread by the time it is discovered. By then it may be too late to save the patient.
No one knows yet exactly why the lung cells suddenly become cancerous. However, there are some clues. Lung cancer is rare in people who do not smoke.
In spring and summer when the sun shines most of the day a large number of people have freckles. They are caused by the sunshine. It stirs a brownish pigment which normally lies in the deep layers of the skin and the pigment comes to the surface where it can be seen.
The skin is not just a thin jacket to cover the body. It is a complex organ with many functions. It has oil glands and sweat glandsand very small roots from which hairs grow. It has blood vessels and nerves. Its thickness may be from one-sixth to one-fiftieth of an inch.
The outer layer of the skin, called the epidermis, is a thin tissue of cells constantly coming off. The cells grow in the lower layer called the dermis. In the dermis there is a brown pigment.
The sunshine brings a spot of the pigment from the dermis to the epidermis where it can be seen as a freckle. Freckles disappear when old cells of the epidermis come off, and new cells which have grown in the dermis take their place.
Tags: Skin Care
The most important part of the nervous system of a human being, is what may be called the new brain. It is so large, and has grown out so far in all directions, that the whole part of the old nervous system is under it. Ordinarily when we talk about a man’s brain it is entirely of this new brain that we are thinking. The proper name for it is cerebrum.
The first glance at the cerebrum shows that it is a double organ. It has a right half and a left half. These two are alike, though it seems that in right-handed people the left half, and in left-handed people the right half is slightly larger.
If we separate slightly the two halves of the cerebrum and look down between them, we see a mass of white nervous tissue running across from one side to the other. This is a bridge between the two halves of the brain by which they are made to work and act as one. When we look at the surface of the brain we see at once that it is very much folded. The folds vary in depth and length but on the whole they form a definite pattern which is the same on both sides of the brain, and its main lines are the same in all human beings.
The surface of the brain is the all-important part. The brain in the animal world increased until it has reached the size it is in the human head. This means that there has been a great deal of room required to house the brain.
Therefore the skull has also become bigger. But the brain has grown more quickly than the skull, and the surface has been deeply tucked away here and there. There is as much or perhaps, more, of the surface of the brain tucked away than shows on the outside. The higher the type of brain, the more its surface is folded. As animals have become more and more intelligent, the surface of the brain has become more folded.
When we cut through the cerebrum of any of the higher animals, we find that it consists of an outside layer which is grey and an inside layer which is white. This grey layer is often called the mantle. It is the real brain, and it is the most wonderful thing of which we have any knowledge. It owes its grey colour and all its meaning and wonder to the fact that it is principally made up not of nerve-fibres, but of nerve-cells. The rest of the brain is made up of nerve-fibres or nerves which give the inner layer a white colour. The grey mantle contains comparatively few nerve-fibres which connect its different parts.
Several layers of cells are found in any part of the grey mantle. The cells differ in different parts of the brain. When examined, corresponding parts of the brain in a large number of animals of quite different kinds show the same arrangement of cells. If a microscope slide containing a large number of cells shaped liked pyramids and arranged in a certain way were shown to an expert, he would rec¬ognize them as belonging to that part of the brain which controls the movements of muscles, though he might not be able to state what kind of animal it was taken from. The whole of the surface of the brain has been mapped out. In the brain we find centers for the motion of muscles, for feeling, sight, hearing, taste, smell, etc. In the lower kind of animals, the whole brain practically consists of these various centers. They make the brain. But as the brain gets bigger it is not the centres that get bigger, but they become gradually separated from one another by the growth of new parts of the brain between the old centres. The process goes on and on, until at last in mankind — and only in mankind — it has reached the stage at which vari¬ous special centers have become mere patches that lie here and there on the surface of man’s huge brain. These newer areas often called the silent areas play a very important part in the functioning of the brain. The nerve-fibres from them run in every direction. They run in definite groups and by definite ways to the other centers of the brain. They are the associate fibers. They associate one part of the brain with another.
If we compare the spinal cord of a dog with that of a man, there is not much difference between them. If we compare the cerebrum of a dog with that of a man, we find that the difference consists mainly in association of fibers and cells.
The grey mantle in the case of a man is much thicker. It is the greater number of association cells that makes it thicker. Generally, we may say that the difference between a high brain and a low brain is: that in the special centers the grey mantle is thicker in the high brain because there are a great many association cells in it, and that in the high brain the special centers are forced apart by the growth between them of new parts of the brain which bring all parts of the brain into connection with one another.
What function is performed by sweat? Why does the organism give it off in such large quantities? It is the mechanism by which a human organism protects itself against overheating. Evaporation uses large amounts of heat, 600 calories per litre of sweat. If all this heat were given oil by a human body, its temperature would fall by approximately ten degrees. Unfortunately, our body expends only a small proportion of its heat on evaporation and, therefore, sweating cannot ensure cooling of the body, but can only protect it against overheating. Normal body temperature, about 37°C (in the armpit), is only maintained due to the evaporation of water from the lungs and skin, even when the temperature of the ambient air is as high as 40 or 50°C.
Sweating is not always beneficial. When humidity is high, sweat evaporates very slowly. It collects in large drops and flows over the body surface bringing no relief as there is no cooling without evaporation. For this reason heat is easier to tolerate in dry deserts than in damp tropical forests.
Is it harmful to sweat a lot? Loss of three to five litres of water, whatever the cause, brings about intolerable thirst, but this is not fatal if it is compensated sufficiently quickly. There was a well-known case in France in 1821 when a man doomed himself to death by stubbornly refusing to drink anything. The struggle between life and death continued for 17 days. The man could have been saved had he been given sufficient water to drink, even as late as the fifteenth day of his amazing fast.
Where does the water contained in sweat come from? Where does man store the liquid he has drunk? Sweat glands draw water from the blood. As long as sweating is not excessive, the blood does not become thicker and no decrease occurs in its volume. But as soon as the water content of the blood begins to drop, the same amount of water flows into the blood vessels from the stores. (The chief sites of water storage are the subcutaneous tissue, muscles and other organs.) Conversely, the water consumed by man is absorbed by the blood from the intestines; the corresponding amount of water is immediately transported to the stores.
The amount of water which can be stored in the body is limited, especially in birds and flying insects. It is scarcely enough to ensure the vital functions of the organism for a day or two, even in cool weather. But there must always be a reserve of water in the organism. The most original method for storing water has been invented by bees. A bee family, consisting of one thousand adult insects and a great number of larvae, cannot exist without water. What happens to the young when non-flying weather occurs? The bees have found a way out. If you open a hive you can see large worker bees hanging motionlessly on the combs. They are living reservoirs of water. The bee water-carriers pour the excess water into the crops of the worker bees till they become too heavy to fly or crawl. After a day or two of non-flying weather their abdomens return to size and the reservoirs become empty.