What is plastic surgery?

    Plastic surgery is a surgical operation which is conducted to correct physical deformities in skin whether congenital or sustained in some accidents. This is done to remove the ugly spots from the face. The ugliness of the skin arising out of burns, cuts or small-pox can be removed by plastic surgery.
Sometimes you must have noticed that the upper lip of a child is slit since birth. With the help of plastic surgery the soit portions of the lips can be so nicely joined that you will not be able to detect the deformity. In the picture shown above you can see a child with his upper lip cut since birth, but it has become normal after plastic surgery.
    Plastic surgery done for beautification is called cosmetic surgery or beauty surgery. With its help the scars caused by small-pox or the wrinkles on the face can be removed. The shape of the breasts can be modified according to one's wish. This is also used for reducing the thickness of the eyelids and the lips. The shape of the chin and the nose can also be corrected by plastic surgery.
This type of surgery was also practised in india thousand of years ago.In ancient times,a criminal's nose used to be chopped off as punishment.In those times,there were plastic surgeons who would form new nose by grafting skin from the cheeks.The modern plastic surgery was started in America in nineteenth century.
Do you know how the plastic surgery is performed?For plastic surgery skin of the surgery size is cut off from a healthy part of the body and grafted on the affected part.For this surgery,only two layers of skin are removed,because these have greater capacity of cell division at the new places.
These days the facilities of plastic surgery are available in government hospitals and private clinics of all the big cities.Hundreds of operations are performed every day in these clinics for enhancement of beauty alone.

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Why does ice float on water?

    It is a matter of common experience that ice floats on water. Howsoever large the size of ice may be, it will not sink. Even icebergs keep on floating in the sea. Do you know why ice floats on water?

    The law of floatation of bodies was given by the Greek scienctist Archimedes. According to this law, whenever a body is placed in water, it is acted upon by two forces-the weight of the body acting downwards and the buoyant force of water acting upwards. If the weight of the body is equal to or less than the upthrust of water, the body floats on water. In other words, if the weight of the body is equal to or less than the weight of the water displaced by it, it will float on water. On the other hand, if the weight of the body is more than the weight of water displaced, the body will sink in water. Hence a body floats when its weight is equal to the weight of water displaced by it. Since the weight of wood is half of the weight of equal volume of water, that is why half of wood is under water, while the other half is above water. Similarly, the weight of cork is one-fifth of the weight of the water displaced by it, so one-fifth of cork is under water while the rest is above water. You can understand the floatation of ice also, on the basis of this law.
    In general, when a liquid changes to solid, it contracts because its molecules come closer to each other in the solid state. As a result of this, the volume of the substance decreases or its density increases. Hence a substance becomes heavier in solid state, than in the liquid state.

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Are ghosts and evil spirits a reality?

 Every race or religion has some degree of faith in the existence of ghosts and evil spirits. Quite frequently, newspapers publish stories throwing light on the existence of ghosts and evil spirits. Some people claim to have even seen them.

    According to the Hindu religion-they are a separate species. After death, man may become a ghost or evil spirit depending upon the quanlity of his deeds in this world. They have no specific form, but they can assume any form. They are not visible to the eyes. They can become visible or invisible anywhere. It is believed that generally they live in the ruins of buildings, burial places, ponds, deserted wells, solitary places and on peepal, banyan trees etc.
    In many races some rituals are performed after the death of a man or woman with a view to ensure that the ghost of the dead does not harass the living ones.
    But the scientists have a different view in this matter. They treat their existence as a figment of imagination. According to scientific facts, this is either an illusion or hallucination of the mind and eyes. In illusion, something does exist, but our mind and eyes take it to be something else. Mirage in a desert is an example of illusion. The thirsty deer sees water pools some distance away in front of it-it tries to reach the water to quench its thirst. But the water seems to recede further away. The deer gets lost and dies. This illusion of fwater in the desert is caused by total internal reflection of light. As a matter of fact, water does not exist there, but due to the total internal reflection of light, the inverted images of trees and plants give an impression of water.
    In hallucination, nothing exists in reality. This is caused by some anxiety or tension in the mind. Some intoxication medicines also cause hallucination. In hallucination, man hears different voices, sees peculiar creatures and sometimes he sees frightening, gigantic faces whom he considers to be ghosts. Under the influence of cocaine, one feels as if some insects are crawling on the skin.
    Scientists have, therefore, concluded that ghosts are an illusion or hallucination of the mind. They don't have a real existence.

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Do ants also have their kingdoms?

    Do you know that the ants have their own world?-they also have cities and live in groups like us. They also have kings and queens and servant ants for doing various jobs. They have armies which are capable of facing the biggest of the big animals.

    More than two thousand kinds of ants have been studied so far. The biggest ant is found in Africa. It is three inches in length. Ants live in groups. Their groups are both large and small. These groups are found everywhere.
    Every class of ants has a separate army which attacks the ants of other classes. Strong ants drive out the weak ants from their holes and capture them. They even capture their eggs and when ants come out from these eggs, they use them as their slaves. Millions and millions of ants of one category live like one country. They have a king and a queen and various other functionaries. The king looks after the administration, while the queen takes various types of work from the slave ants. The slave ants are engaged in service for their whole life time. The male and the female ants contract marriage also. The farmer ant manages food for other ants.
    Some classes of ants are very cruel. There is a class of ants found in central Africa, south America and south Asia, which is non-vegetarian. These ants come out in groups of millions in search of their prey and if some animal falls in their trap, they eat away all the flesh of that animal.

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How does the owl see at night?

    There are all kinds of birds in the world and owl is one of them. what is peculiar about this bird is that it can see more clearly in the night than in the day. Its ears are also very sensitive. At night if there is a slighteset movement from any of its prey, it can detect and catch it very easily.

Its legs have four claws with curved nails which specially facilitate it to seize its prey. Mice are its favourite food.

    Owls are found almost in every part of the world. In some countries they are treated as inauspicious birds, while in some others they are regarded as symbols of wealth and wisdom. It is a bird that really comes to life at night and its whole body is especially suited to nocturnal activity. The birds having clearer vision in the night are called nocturnal birds. On the other hand the birds which can see clearly in day time are called diurnal.

    You must be very curious to know how this bird can see so clearly at night.

    To understand this, it is essential to know how we see the things. Light scattered by every object is focused on to the screen of the eyes by the lenses inside the eyes. This screen of the eyes is called the retina. An inverted image of the object is formed on the retina which is carried to the brain by optic nerve. This is erected by the brain and we see the object. The owl's eyes have four special features, due to which it can see more clearly in the night. Firstly, the distance between the lens of its eye and the retina is more than the distance in the case of our eyes. Due to this, the image formed on the retina is bigger in size. A special organ of its eyes named 'pecten' assists in focusing the lens i.e. in adjusting it for various distances. Secondly, the number of 'rods' and 'cones' (special cells) in the retina is very large-almost 10,000 per sq mm compared to 2000 per sq mm in our eyes. Thus, the owl can see five times more than us. Thirdly, its eyes have a red coloured material, chemically a prote,which makes its eyes more sensitive to light. Fourthly, the pupils of its eyes can dilate more, thus allowing even the smallest amount of light to enter the eyes. Due to these four factors, the owl can see more clearly in the night.

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How does the tongue tell us the taste?

Man has five senses of perception-eyes, nose, ears, skin and tongue. The tongue tells the taste.

    The tongue is located inside the mouth. It is narrow in the front side, while broader in the rear. It is an important muscle in the body. It is red in colour. If you examine it minutely, you will see granular lumps on its upper surface.
They are called taste buds. These taste buds are composed of cells. There are hair-like fibres coming out of their upper ends.

    These taste buds are of four kinds, telling us four main tastes-sweet, bitter, sour and salty. The front portion of the tongue is sensitive for sweet and salty tastes, the back portion is for the bitter and the edges of the tongue are for the sour taste. The central portion is not sensitive for any taste because it does not have taste buds.

    The taste of food is known only when it is in liquid state. A portion of the food is dissolved in saliva which activates the taste buds. A chemical reaction produced by the food material generates nerve impulses. These impulses reach the 'taste centre' in the brain which ultimately gives the feeling of the taste. In addition to the tongue, other senses also help in the perception of the taste of food. The smell is also a part of the taste and felt by the nose. It is why one does not enjoy the total taste of food when one suffers from cold or influenza.

    The number of taste buds on the tongue of an adult is more than on that of a child. The tongue of an adult has about 3000 taste buds. However, with the advancement in age, the taste buds start losing vitality and finally become almost inactive. The number of taste buds is reduced to just 400 in the case of a seventy year old man.

    Due to constipation or indigestion, some impurities deposit on the tongue and they prevent the food particles from reaching the taste buds. Hence the taste of the food seems to be changed. Body fever and hot food also deactivate the taste buds and thus the food does not give its real taste.

    In the case of winecocoa and fruit juices, it is the smell which helps in the realisation of the real taste. When these liquids are taken into the mouth, the tongue expeiences the taste while their smell enters the nose and through the 'smell nerves' it reaches the brain. In this way he total pleasure of the taste is derived.

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