My Science School

We take a grip on things by using our muscles to exploit the development of the human thumb. The importance of this thumb is that it can be moved across the palm of the hand to touch the index finger. In contrast the digits of a monkey’s hand are more rigid. This difference explains why a human being can handle an instrument with such precision.

     The mechanism of the hand is operated by way of the wrist, a hinge joint composed of eight small bones (carpals) packed firmly together to give elastic stability. Below the wrist project five small, long bones (metacarpals) which give the palm firmness. Four of the bones have hinge joints and are connected to the thumb allows it to move round and meet the fingers and palm, thus providing a firm grip.

    Possession of such a hand has enabled man to form a society and culture based on the use of tools. It is thought the hand developed from the five-rayed forepaw of an early vertebrate. However, occasionally a child is born with an extra tiny thumb or little finger and some people believe that the forepaw was originally seven-rayed.

    The human thumb has length longer in proportion than that of an ape. About 92% of human being is right handed, but apes tend to use both hands with equal ease.

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Inside the womb of a pregnant woman or animal a placenta is formed, through which the unborn baby is nourished. The baby is connected to the placenta by the umbilical cord, which is joined to the unborn child at the navel.

     The umbilical cord is the baby’s lifeline. Everything the child needs to survive will pass through it- air, blood and nourishment. At most it is no more than an inch wide and, perhaps, only a foot long.

    Once the baby is born the placenta, which serves a purpose only during the pregnancy, will be discarded.

      The umbilical cord will be cut with scissors a few inches away from the newborn baby’s stomach. This is quite painless because the umbilical cord has no nerves. The baby will now breathe on its own.

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The most likely places to catch malaria would be in tropical and sub-tropical countries, especially in the forested parts of Central Africa, Asia, and southern Europe. This is because the female anopheles mosquito, whose bite transmits the diseases, breeds in the warm, stagnant, marshy pools found in those parts.

    Malaria is said to derive its name from the Italian for “evil air”. It causes chills, fever and anaemia, and is sometimes fatal. In India a million people are likely to die from it every year.

     The first effective remedy for it, quinine, was used in the 16th Century. It is an infusion from the bark of the cinchona tree. Modern drugs, too, have greatly reduced the threat of malaria. In particular the use of sprays on the mosquitoes breeding places has been highly effective.

    In 1955 the world Health Organization started a mosquito-eradication programme of benefit to nearly 1,200 million people.

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Dizziness most commonly occurs when a person who has been moving around with speed stops suddenly. The sensitive liquid in the inner ear, which mainly controls balance, continues to move around for a time after the body has stopped. So the surroundings appear to be still in motion. However, it takes only a few seconds, for the fluid, and balance, to settle.

    This sensation, which is also called vertigo, may also occur to someone looking down from a height or on board ship. Here the cause is probably not so much physical as a nervous reaction which affects the fluid in the inner ear.

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The body temperature of a human being is an indication of his physical condition, so that an abnormally high or low temperature is generally a sign that something is wrong.

     The normal temperature is usually given as 36.90 C. (98.40 F.), but as the body temperature varies throughout the day, anything between approximately 36.70 C. (OR 98.10 f.) and 37.20 C. (or 99.00 F.) may be taken as normal.

    For instance, the temperature rises after a large meal, during hot weather and after violent exercise. Your temperature is at its lowest at night when you are asleep.

    Control of body temperature is exercised by a centre in the brain which ensures that a balance exists between heat production and heat loss. A raised temperature is often the sign of bacterial or virus infection. It may be due to heatstroke, to certain types of brain injury or disease or to shock.

     A very high temperature, or fever, may begin with a “rigor” (an attack of shivering and cold), in which the whole body may tremble uncontrollably and the teeth chatter. Although at this stage the skin feels cold and clammy, the temperature within the body is raised. Soon the skin becomes hot and dry, pulse and breathing rate are speeded up and there is a feeling of exhaustion, aching muscles. Headache, thirst and perhaps delirium and loss of the sense of time.

    Finally this stage is succeeded by profuse sweating and a gradual relief of the symptoms.

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Blood congeals when a part of the body is wounded. If it failed to congeal the injured person would die from loss of blood.

    The congealing, or coagulation of the blood, is the first step towards healing a wound. It closes the wound and builds a scaffold for new tissue by means of a chemical process in the plasma, the fluid part of the blood. In this process the platelets (small cellular bodies in the blood) produce thromboplastin. This changes fibronigin, a protein in the blood, into fibrin. Finally a spongy network of fibrin connects the edge of the wound and prevents the loss of any more blood cells. Often, a scab is formed over the wound as a protection.

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We become sea-sick because our balancing organs, the labyrinthine portions of the inner ear, are disturbed by out-of-level movements, by sudden turning movements, or by sudden changes in movements in a straight line, either horizontal or vertical.

       The ear has three semicircular canals, filled with fluid and set on different planes in the ear. When sudden movements occur, each canal is affected differently. As a result, nerves in the canals send conflicting information to the brain, so giddiness is likely to occur.

        Nowadays, seasickness comes under the general heading of motion sickness a name invented by Sir Frederick Banting in 1939, which include the discomfort people feel while travelling in all kinds of vehicles.

    Sea-sickness may vary with individuals from slight uneasiness to complete prostration. The symptoms are pallor, cold sweating, nausea and vomiting. People who have lost their ear labyrinths because of disease do not become seasick. Others become resistant to it. We say they develop their “sea-legs”, but it would appear to be an adjustment of the central nervous system rather than the organs of balance. Some people find it helpful to keep their gaze firmly fixed on a steady object.

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X-Rays are electromagnetic rays of very short wavelength which can penetrate matter through which light rays cannot pass. We call this opaque matter. An X-ray photograph shows a picture of the internal structure of the body allowing doctors to diagnose broken bones and examine the organs of the body. In order to show the position and shape of the stomach and intestine harmless liquid containing barium is swallowed, and other opaque substances may be injected to show the outlines of other organ. Oxygen can also be injected into the brain to make its outline sharper.

        The discovery of X-rays was recorded in January 1896 by Professor Rontgen, Professor Physics at Wurzburg. Chest X-rays led to the early diagnosis of pulmonary tuberculosis and from these beginnings the science of radiography and radiotherapy developed until now countless X-rays installations are in daily use throughout the world. X-rays are used both to diagnosis and to treat deep-seated diseases like cancer. Scientific laboratories use them in experiments while industry uses them in work of investigation. By using high-tension apparatus giving up to 300,000 volts, steel can be examines for faults and hidden weakness can be discovered in aero plane construction.

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Electric shock treatment, or electroconvulsive therapy, is sometimes used with people suffering from mental illness in which severe depression is the main symptom.

      It was first used in 1938 by U. Cerletti and L. Bini in Rome, and was recommended for the treatment of manic-depression and schizophrenia (literally, “splitting of the mind”).

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The brain directs and coordinates movements and reflexes, registers sensations and is the supreme nervous organ by which man acquire knowledge and the power to use and adapt it. It shapes our personalities, and without it we would be more helpless than the tiniest human baby.

       There are three main parts of the brain: the forebrain (or cerebrum), the midbrain and the hindbrain. They have the consistency of soft jelly and are protected by three membranes (meanings), a tough outer envelope called the dura and a water fluid (cerebrospinal fluid) which acts as a support and a cushion. The brain is connected to the spinal cord, and its surface is highly convoluted.

      The cerebrum which forms nearly nine-tenths of the brain is divided into two halves (hemispheres). Generally the left half of the cerebrum controls the right half of the body, and the right half of the cerebrum controls the left half of the body. Some areas are connected with the special senses of man, but there are so-called “silent areas” which scientists believe are connected with memory and the association of ideas. The thalamus, a mass of grey matter which is buried in the cerebrum, is the source of instinctive feelings and emotion.

    The midbrain is concerned with eye-movements, while the hind-brain contains the nerve cells responsible for breathing, heart action, and digestive juices and so on. The cerebellum, a part of the hindbrain, plays an important role in the execution of the more highly skilled movements.

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A sheet of paper consists of vegetable fibers of different sizes, twisted and intertwined with each other and finally squeezed together to make a sheet with a surface smooth enough to write or print on.

        Originally it was discovered that if a mixture of wood pulp and water was spread on a sieve, the water would drain away and leave a deposit which, when dry, could be peeled off as a sheet of paper.

Although the Chinese had been using paper since A.D. 105 it was not introduced into Europe until the 15th century. The raw materials used for modern hand-made paper are cotton and linen rags. Such paper is very expensive to produce.

     Machine-made paper is processed in paper mills from esparto grass, wood and straw, and is much cheaper. The materials for both types of paper-making have to be put through the same basic procedure of repeated washing and bleaching to get rid of impurities.

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Pollution is a problem because man, in an increasingly populated and industrialized world, is upsetting the environment in which he lives. Many scientists maintain that one of man’s greatest errors has been to equate growth with advancement. Now “growth” industries are being looked on with suspicion in case their side effects damage the environment and disrupt the relationship of different forms of life.

       The growing population makes increasing demands on the world’s fixed supply of air, water and land. This rise in population is accompanied by the desire of more and more people for a better standard of living. Thus still greater demands for electricity, water and good result in an ever increasing amount of waste material to be disposed of.

    The problem has been causing increasing concern to living things and their environment. Many believe that man is not solving these problems quickly enough and that his selfish pursuit of possessions takes him past the point of no return before he fully appreciates the damage. It would then be too late to reverse the process.

    Ecologists say we are so determined to possess a new car or washing machine, or to obtain a greater yield from our crops by the use of fertilizers, that we ignore the fact that life depends on a lot of micro-organisms working efficiently.

     For example, if new chemicals were released into the environment, a combination of them might well poison one or more of the different type of bacteria in soil and water, which are essential to keep nitrogen being circulated from the air into organic material, and being cycled back into the air again. If this should happen on a world-wide scale, the air would become unbreathable.

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Fertilizers are used on farms to increase crop yields by ensuring that soils contain the chemical elements required by growing plants. These chemical elements include oxygen, carbon, hydrogen, nitrogen, phosphorus, potassium, sulphur, calcium, magnesium, and iron. If soils are lacking in any of these, the deficiency can be made good by the right fertilizer.

     Until the 119th century, farmers relied mainly on the application of natural fertilizers put “goodness” back into the land. They used manure from the stock-yards and, in the case of coastal areas, seaweed from the shore. Lime was also applied to prevent acidity. This method of soil rejuvenation went a long way to maintain the presence of chemical elements. But it often did little to improve soils already lacking in certain chemicals.

      Nowadays soils are analyzed to find out deficiencies which can be made up by the application of the appropriate chemical fertilizers. Of course, the chemicals alone do not guarantee a successful crop. The continued application of the natural fertilizers, such as manure and humans (decayed vegetables matter) is also essential.

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The night vision of Owls is 100 times as keen as that of human beings, because their eyes are especially adapted for seeing in the dark. But most are almost colorblind and the pictures they receive are slightly blurred. This is because their eyes contain more rod-shaped receptor cells than cone-shaped ones.

        Operating in bright light, cone cells sharpen details and react to colour. Rod cells gather light and owls have 10times as many of these as do human beings. Each cell contains “visual purple”, a substance capable of transforming the slightest glimmer of light into a sight impression.

   Owls have exceptionally large eyes and can control the amount of light entering by expanding or contracting the pupil. Each pupil can act independently of the other so that owls can see objects in the shadows and in bright light at the same time. Owls’ eyes are so large that they are supported by thin, bony, and tubular structures called sclerotic rings. Because of this the eyes are almost immovable and nature has compensated for this by giving owls extremely flexible necks, which enable them to turn their heads through an arc of 270 degrees.

     These birds have excellent binocular vision as their eyes are in the front of their heads. This gives them a tremendous advantage in swooping on small lively prey, because distance judgment depends on binocular vision. To add to their advantages at night, the owls have outstanding hearing, keener than that of any other carnivorous bird.

    But owls can also see well in the daytime. Although most species hunt by night, others are active at dusk or in full daylight.

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    An atoll or coral reef begins to form when tiny marine animals called coral polyps attach themselves to rocks on the sea bed. the reef, which eventually takes the shape of a ring or horseshoe enclosing a lagoon, is made up of the lime-based skeletons of in-numerable polyps.

    After building skeletons round themselves, coral polyps produce new polyps, which in turn surround themselves with skeletons. The young polyps remain attached to the parents so that succeeding generations combine to produce a great mass of coral.

    Atolls occur only in shallow water where the temperature is over 65 f (18.3 C). They are found in the West Indies, the Indian Ocean, along the coast of Brazil and, notably, in the pacific. North-east of Australia huge reefs have formed and some atolls may stretch 40 miles in diameter and more than a thousand feet in depth.

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