Why are people dwarf?

Generally most of the people are of normal height, but sometimes we come across people who are exceptionally tall or small. Persons who are exceptionally small are called dwarfs. In circus you must have seen such dwarfs who entertain you.

Do you know why some people lack normal height? The growth of a person depends on many factors. Heredity plays an important role in determining the height of a man or a woman. Children of tall parents will be tall while dwarf parents will have dwarf children. In Africa, tribes such as the Watusi and the Masai have many men 200 cm tall. At the same time, there are Pygmy tribes in Africa, whose people are about 130 cm. These variations are due to heredity only. Disease is also a reason causing dwarfness. There are cases of dwarfness in which head and trunk are normal in size, but arms and legs are short. This is caused by disease of cartilage. A normal body skeleton increases in length during childhood and adolescence because cartilage changes into bone at the growing ends of the bones. Disease of the cartilage prevents arms and legs from growing to a normal size. Dwarfness is often caused by the lack of hormones produced by pituitary gland. The under activity of pituitary gland during childhood does not allow the body to grow in normal manner. This type of dwarfness can be treated by injecting hormones. Too much or too little growth is also determined by some disorder in adrenal, pituitary, thyroid and male and female sex glands (testes and ovaries).

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How far can a kangaroo jump?

Kangaroo is one of the strangest and oldest species of four footed animals on the earth today. They are found in Australia and that is why Australia is often called the "land of the Kangaroos".

A few thousand years ago, there was a kind of kangaroo in existence which was nearly as large as a horse. The kangaroo is the best known of the 'marsupials', which means, "animals with pouches". A full grown kangaroo stands about six feet tall. Its front legs are short while the hind legs are very long. These powerful hind legs enable the kangaroo to take long jumps of 3 to 5 metres at a time. The kangaroo has a long tail of more than one metre. It uses its big tail to rest and to balance itself while jumping. If a hunter or a hunting dog chases a kangaroo, it runs very fast making long jumps. It can cover a distance of 7 to 9 metres just in one jump. When a kangaroo is cornered by hunting dogs, it can seize a dog with its forefeet and kill it with one swing of its hind feet. The female kangaroo has a pouch in its belly in between the hind legs in which it keeps its young ones till they grow up. When a baby kangaroo is born, it is a tiny pink, naked mass of about 2.5 cm in lengh and weight about 1 gram. Not only the infant kangaroo, but even younger kangaroos need the protection of their mothers. A kangaroo lives on the mother milk until it leaves the pouch at the age of 6 to 8 months. A kangaroo lives about 6 to 8 years. Finding the young ones in danger, the mother kangaroo lifts them by mouth and places them inside its pouch. The kangaroo is a meek animal like sheep and goats. Like the hare, it is unable to see an object just in front of it. But its power of smelling and hearing is quite strong.

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How does a prism produce rainbow colours?

The sunlight which seems to be white is composed of seven colours. Issac Newton, father of physics proved it for the first time in 1666. He demonstrated with the help of a glass prism that sunlight comprises violet, indigo, blue, green, yellow, orange and red (VIBGYOR) colours.

The question arises: what is a prism and how does it separate the seven colours of white light?
Prism is made of transparent glass with three faces. Two of them are triangular and remaining one is rectangular, each edge making an angle of 60 degree. If we see an object through a prism, it will look multi-coloured. Whenever a ray of light passes through a prism, it deviates from its path and bends towards the base of the prism. This property of bending of light from its path while passing from one medium to another medium is called 'refraction' of light. As already said, white light is composed of seven colours. While coming out of the prism, these different colours deviate at different angles. These colours constitute what we call the spectrum. The red colour deviates least from its path whereas violet colour deviates maximum. That is why the red colour occupies the uppermost part of the spectrum, while violet the lowermost. Other colours are in between these two. Separation of white light into seven different colours is called the dispersion of light. These are the same seven colours seen in a rainbow. This is how a prism disperses white light into the seven rainbow colours.

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Why do the eyes of some animals shine in the dark?

Have you ever seen a cat sitting in the dark? Though its body is not visible, yet its yellow eyes shine in the darkness. The eyes of tiger, cheetah, leopard, lion etc. also shine in the darkness of the night just like the eyes of a cat. Besides these, there are many other animals whose eyes shine in the dark, but our eyes do not. Do you know why?

The eyes of these animals have a thin layer of some special crystalline substance which reflects the light falling on it. This reflected light is the cause of the shine. In the night, even the smallest amount of light falling on this crystalline surface gets reflected and we see the shining eyes. Animals with such eyes can clearly see things in darkness. They are called nocturnal animals.
Studies mad on cat's eyes have shown that behind their retina, there is a crystalline layer called the 'luminous tapetum', which reflects light. Due to this layer the cat can see clearly in dim light and its eyes shine in the dark when the light is directed on them. There are many animals whose eyes do not shine because their eyes are not gifted with this crystalline layer.
It has been observed that the colour of the shine is different in different animals. It depends upon the number of blood vessels present in their eyes. If the number of blood vessels is large the colour of the shine is red and if the number of blood vessels is less the colour of the shine is white or pale yellow.

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What causes people to faint?

We often see that people faint on hearing some sad news or on getting frightened suddenly. They get drenched in their sweat and their bodies become cold. Their faces turn pale. Physical consciousness diminishes. Unconsciousness can be caused not only by a shocking news or terrible fear, but by many other factors also. People may faint because of confinement in a close and poorly ventilated room,

or because of hunger, fatigue, severe pain, emotional shock or for many other reasons. Now the question arises: why do people become unconscious?
In order to know the reasons for fainting, it is essential to know what consciousness is. For the normal functioning of the brain, it is essential that there should be proper circulation of activities remain normal. The normal functioning of the brain is in fact consciousness. If there is some obstruction in the supply of blood to the brain, the common physical processes get disturbed. Whatever may be the cause of fainting, man will become unconscious when normal supply of blood to the brain is disrupted. Hence we see that unconsciousness is due to the insufficient supply of blood to the brain.
The state of unconsciousness can be prevented by some measures. If somebody feels that he is about to faint, he should immediately lie down. If that is not possible, he should bend downwards and enclose his head in between the knees. Both these measures enhance the blood supply to the brain and as soon as the brain starts receiving proper quantity of blood, the chances of one's becoming unconscious reduce.
If somebody has become unconscious, he should be laid down and his clothes should be loosened. His head should be kept a little lower, while the legs should be raised a little high. This will increase the blood supply to his brain and he will regain consciousness. Once he is conscious, he should be given tea or coffee. If somebody has fainted because of head injury or heat stroke, he should be taken to the hospital immediately.

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What happens to our body in sleep?

Sleep is as important to the body as food, water or air. After a whole day's toil, both brain and body get tired. Sleep is necessary to restore energy and freshness to the tired organs and tissues of our body. It restores our vitality and refreshes us again.

Do you know how sleep comes to us and what happens to our body during sleep? According to scientific facts, there is a very complex area in the brain called "sleep centre". Calcium ions present in the blood, control this centre. When an optimum quantity of calcium is received by the "sleep centre", we get sleep. It has been observed from experiments on animals that they start sleeping when calcium is injected directly into the sleep centre. But if calcium is injected into the blood stream, this does not happen. So it seems that the sleep centre must first be "sensitized" by certain chemical substances, produced when we are tired, before it would react to calcium and put us to sleep. During sleep, the sleep, the sleep centre does two things. Firstly, it blocks off the brain so that we have no will-power or consciousness and secondly, it blocks all nerves leading from the brain so that our internal organs and limbs fall asleep.
In sleep, our body does many types of movements. A man on an average changes his sides 20 to 40 times during sleep in one night. Blood circulation continues during sleep. Heart beat slows down a little bit. The digestive system works normally. Liver and kidneys perform their functions. The effect of sound, liht, heat, smell etc. in sleep are the same on every sleeping person. During sleep, the body temperature is lowered by about one degree centigrade. During sleep the body cells are quietly engaged in getting rid of waste materials that have accumulated during the active part of the day.
How many hours a healthy person should sleep? The number of hours needed varies with individuals. the average adult needs from 7 to 9 hours of sleep. Boys and girls of 15 years of age need about 10 hours sleep each night. It is wise to form the habit of going to bed at the same time each night. If you have trouble in getting sleep. you should not take sleeping pills unless prescribed by the physician or medical practitioner.

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How long can man survive without food?

Like air and water, food is also essential for all living beings. From the smallest insects to the biggest animals-all need food for their survival. So much so that even plants and trees can not live for long without food. Most of us feel upset if we skip just one meal, and if we try to go without food for 12 hours we would really be uncomfortable.

Energy required for doing work is obtained from food. Cells and tissues damaged in working are repaired by it. It is very much needed for the growth and development of the body. In short, food is very essential for the proper functioning of the body.
Now the question arises how long can we survive without food? There are some animals which can store food in their bodies and live on it for a long time. It has been observed that the smaller and the more active is the animal, more rapidly it consumes its stored food. Warm blooded animals use up their stores of food in the body more quickly. A dog can survive without food for 20 days at the most. However, the bug is such a wonderful creature that it can survive without food for one full year.
But man cannot store food in his stomach. If he misses one meal, his condition is bad. Food is required to maintain the flow of blood. All the constituents of blood are obtained from food. The moment, the blood lacks nutritional materials, a signal, via blood, goes to the hunger centre of the brain and we start feeling hungry.
There are few examples of persons who survived for a very long time without food. Angus Warviern of Scotland survived without taking any food for 382 days i.e. from June 1965 to July 1966. During this period, he took only coffee, tea, water and soda water. One south African woman survived for 102 days on water and soda water only. Stefan Taylor of New Zealand remained alive for 40 days in 1970 on a daily intake of one tumbler of water only. These are some uncommon examples. Such people are endowed with exceptional power. Common man can at the most survive without food for a week.

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What is Regeneration?

Would it not be wonderful if people who lost an arm or a leg or even a finger in an accident could simply grow another one in its place? But in reality it does not happen in case of human beings. However, you will be surprised to know that there are some living beings in which a new limb

develops at the point from where the original limb has been lost. Development of a new part in place of a lost part is known as regeneration. Some creatures have the unique ability to regenerate their body parts. If small arm of a starfish is cut off or destroyed, it is regenerated. The hydra is also endowed with this wonderful capability of regeneration.
The ability of regeneration is different in different creatures. Living beings with complicated structures have lesser ability of regeneration. Man and other mammals have complex constitution. That's why they have lesser ability of regeneration. Because of lesser ability of regeneration, once our legs or hands are cut, they are not regenerated. Though in our body also, some type of regeneration takes place. For example, if the skin in any part of the body is burnt or cut, new skin comes up there again. Regrowing of wings of birds is another example of regeneration.
In some species new tissues grow from the surface of the wound and replace lost or damaged tissues. Sometimes, the tissues that an organism regenerates, are different from original tissues. The regenerated structure may be smaller than the original.

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How is the Rainbow formed?

During the rainy season you might have observed a bow shaped multicoloured strip in the sky. This is called rainbow. This strip has seven colours-red at the top and violet at the bottom. Other colours lie in between these two. How is the rainbow formed?
The sunlight which appears to be white is actually composed of seven colours. These seven colours are-Violet, indigo, blue, green, yellow, orange and red. The wavelength-wise distribution of these colours is called spectrum. After the rains, the atmosphere is full of small water-drops. When the white light coming from the sun enters these drops, its seven colours are separated. These rain-drops work like prisms. As the prism separates the seven colours of white light, these drops also sweparate the different colours. The separation of seven colours of the sunlight is called dispersion. These colours after being totally reflected from the back side of the rain drops come out as separate colours. When the rays of these colours reach our eyes, they give us the appearance of the rainbow. The rainbow is circular because the sun is also circular. Sometimes a second rainbow can also be seen. This is called secondary rainbow. This is fainter in comparison to the first one and the sequence of its colours is reversed i.e. violet colour occupies the upper most position while the red is the lower most. This rainbow is formed due to those rays which have been reflected twice inside the water drops. The rainbow is generally seen only when the sun is at our back and the cluster of water drops are in front of our eyes, i.e. when we stand in between the sun and the cluster of water drops. It is essential for the formation of the rainbow that the sun is shining after the rain. It is also essential that the sun, our eyes and the centre of the rainbow lie on the same straight line. To remember the order of colours in the spectrum, we should remember the word VIBGYOR. Each letter of this word represents one colour i.e. V for violet, I for indigo, B for blue, G for green, Y for yellow, O for orange and R for red.

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Why does the dog go mad?

 Dog is regarded as a faithful friend of man. But when it goes mad it is most dangerous. Biting by a mad dog leads to death if not treated properly. When a dog suffers from a disease called 'rabies', it goes mad. This disease is caused by a virus which is carried by the air or some wild animals and enters the dog's body through some cut or wound in its skin.
The virus is bullet shaped having a diameter of about 70 millimicron and a length of about 210 millimicron. It moves from the saliva-infected wound through sensory nerves to the central nervous system, multiply there and destroy brain cells. These viruses start showing their effect in 4 to 6 weeks' time. During this period the dog becomes lazy, suffers from fever and has no interest in food. When these viruses affect the brain, the dog gets excited. It growls and barks. saliva froths from the mouth. During this period, the dog can bite anybody. This is the stage when the dog is said to be mad. After such symptoms appear in the dog, it is likely to die within 3 to 5 days. When a mad dog bites a man, the viruses present in its saliva enter the man's body through the wound caused by the biting. Initially the victim experiences mental weakness and uneasiness followed by fever. Anxieties invade him. He suffers from lack of sleep and feels frightened. The muscles in the throat get slackened and he faces difficulties in swallowing food or drinking any liquid. He is afraid of water. That is why this disease is also called 'hydrophobia' which means 'fear of water'. The signs of this disease appear in the victim in one to three months from the time of dog-bite. If the dog has bitten at an upper part like the neck, mouth or head, it may take less time for the symptoms to develop. In cases of dog-bites, the affected portions should be immediately cleaned and arrangements made to start giving anti-rabies injections to the victim within three days of the bite. The dog should be watched for the next five days. If the dog does not die in that period, it should not be treated as a mad dog, and the treatment should be stopped since a mad dog must die within five days. A few years before, a daily injection of vaccine was given for 14 days or longer depending on the severity of rabies infection. In the early 1970s a new vaccine was tested. Now a days 7 to 10 injections are given, in case of a mad dog bite, to persons depending on the location of bite and number of bites on the body. The virus of rabies also attacks foxes, jackals, cats and rats. But they rarely transmit these viruses to human beings, because they have least contact with us.

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