The microscope

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Even the ancients had known that curved mirrors and hollow glass spheres filled with water had a magnifying effect. In the opening decades of the seventeenth century men began to experiment with lenses in order to increase this magnification as far as possible. In this, they were inspired by the great success of other lensed instrument, the telescope, first put to astronomical use by Galileo in 1609.

Gradually, enlarging instruments, or microscopes(from Greek words meaning " to view the small") came into use. For the first time the science of biology was broadened and extended by device that carried the human sense of vision beyond the limit. It enables naturalists to describe small creatures with detail that would have been impossible without it, and it enabled anatomists to find structures that could not otherwise have been seen

The first man, who made and used microscope was Anton von Leeuwenhoek. He was not a professional scientist. In fact, he was a janitor in the city hall in Delft, Holland. He made more than 200 different microscopes, most of which had only one carefully polished lens. With his homemade lenses, he explored all sorts of things and discovered a world never before seen by the eyes of man. He examined milk, water, insects, the thin tail of a tadpole, and many other objects. His discoveries of bacteria, blood capillaries, blood cells and sperm cells made him famous. In 1675 he wrote the description of the microscopic animals that live in water. Leeuwenhoek's microscopes were simple. But his great patience and keen powers of observation brought to light many new facts about living things.

THE MODERN MICROSCOPE.

The microscope of today is far more complicated than those of Leeuwenhoek's time. They are called compound microscopes because they contain more than one lens. At the top there is an eyepiece which has two lenses in it. Then there is a long tube with more lenses at the bottom. These are called objectives. You can choose different magnifying powers by swinging different objectives into position. The usual high school microscope has a choice of two powers. With the low power, you can magnify an object about 100 times. The high power objective with the usual eyepiece can enlarge up to 500 times.

If you wish to examine an object under the microscope you must pass a beam of high light through it. As the light passes through the lenses, it is bent in such a way that a magnifying image appears. For this reason, anything you wish to see must be very thin. If it is too thick, the light will not go through it. Most microscopes have a mirror at the base. This can be moved in any direction. It reflects light up through the object and the lenses. The object, mounted on a piece of glass, is placed on a flat platform called the stage. Then the microscope is adjusted by moving the tube up and down. This places the objective at the correct height above the object. Unless you focus carefully in this way, you can not get a clear picture.

THE ELECTRON MICROSCOPE. There is a limit to the magnifying power of the compound microscope. The very best of them can enlarge an object up to 4000 times. In recent years a new type of microscope has been invented that does not use light. Instead, beams of electrons are passed through the object and a picture is made on film. The electron microscope can give us an image 25,000 times larger than the object. This development illustrates an important principle of science: when a new instrument is invented, it may speed up discoveries in the laboratory. Already, the electron microscope has made it possible to see things never dreamed of by Leeuwenhoek. We may be sure that in the future it will continue to reveal many new secrets of nature.

"Biology and Human Progress” by L. Eisman, Ch.Tanzer.

THE CELL

The unit of protoplasmic organization is the cell. The word "cell" is not a very good choice in this connection, but it has significance in the history of biology. The name was given by Robert Hooke, one of the first scientists having used a newly developed biological tool, the microscope, to the tiny divisions that he saw in thin slices of cork. The cork slice, through the microscope, appeared to be made up of many small compartments, arranged in rows, and reminded him of the tiers of monks' cells in English monasteries. He therefore called each compartment a cell and the name has survived, although it does not accurately convey the picture of a living unit. What Hooke actually saw in the nonliving wall which had once surrounded the living protoplasm, was not the protoplasm itself. His microscopic studies of some other materials, such as feathers, fish scales, molds, snow crystals and fabrics, brought him closer to the sight of living cells but not close enough to see the living substance.

Observations of the classical microscopists and those of their successors on individual cells as parts of organisms, both plant and animal, led to one of the greatest and for the time most useful of biological generalizations, the cell theory. This concept was first brought to general attention in 1838.

It was a natural outcome of the many observations that had been made during the early part of the nineteenth and the preceding centuries. Briefly, it states that all organisms are composed of cells or of a single cell and that all cells, and hence all organisms, arise from division of pre-existing cells. This theory was to biology, at the state of development, what Dalton's atomic theory was to chemistry.

BLOOD CELLS

Blood cells are of three kinds: red blood cells (erythrocytes), white blood cells (leukocytes and lymphocytes), and blood platelets.

Red blood cells are approximately round, disk-shaped with high edges. They measure approximately 1/3,000 of an inch in diameter. The healthy male has about 5 million red blood cells per cubic mil­limeter of blood. A healthy woman has about 10% fewer.

Hemoglobin is the key element in the red blood cell. It is a com­plex protein that requires iron for its formation. Oxygen picked up in the lungs during the circulation of the blood combines loosely with hemoglobin. Then, in every part of the body where it is needed for cell metabolism, oxygen is released by the hemoglobin, which picks up carbon dioxide on the return journey to the heart and lungs.

Red blood cells are destroyed and replaced at a rate of about 1 % a day. These cells are formed in the bone marrow, particularly in the spine and hip bones, the ribs and breast-bone. They are de­stroyed largely in the spleen.

White blood cells are about 1.5 to 2 times as large as red blood cells, which outnumber them by at least 500 to 1. The average number of white blood cells in the healthy adult is around 7,000 per cubic millimeter. In the presence of infection this number may go as high as 40,000. A great increase in the white blood count is al­most always a sign of infection.

White blood cells play the role of scavenger. Most of them en­gulf and devour bacteria and other particles of foreign matter in the blood stream. Hence they prevent and fight infection and aid in wound repair. Pus is made up largely of dead white blood cells.

The names of various different kinds of white blood cells are long and complicated: for example, polymorphonuclear eosinophil. Because they devour bacteria, they are also called phagocytes. White blood cells are made in the bone marrow, the lymph nodes, and other places in the body.

Blood platelets are about 1/3 as large as red blood cells. They are concerned with blood clotting.

(polymorphonuclear eosinophil - полиморфно-ядерный эозинофил)

THE EFFECTS OF LIGHT ON THE HUMAN BODY

Life having been evolved under the influence of sunlight is beyond question. Many animals, including man, have developed a variety of responding to spectral characteristics of solar radiations. On summer coming millions of people living in the north will take the opportunity of darkening the shade of their skin, even at the risk of being painfully burned.

Tanning and synthesizing vitamin D are only the best –known consequences of effects of sunlight on human body. After being filtered by the atmosphere and the layer of ozone the solar radiation that reaches the Earth surface consists mainly of ultraviolet (290-380 nm), the visible spectrum (380-770nm) and the near infrared (770- 1000) nm), owing to removing all ultraviolet radiation with wavelength shorter than 290 nm.

Sunlight’s acting directly on the cells of the skin is well- known. The most familiar pathological response is sunburn and the chief protective response is tanning. In addition to causing sunburn and tanning, sunlight initiates photochemical and photosensitization reaction followed by forming intermediates and damaging the tissues in the body.

Now let us discuss the indirect effects of light on human beings. Changing the level of concentration of cortistol_, one of the principal hormones, is an example of such effect.

The level of cortistol is at a maximum in the morning hours, soon after walking, and drops to a minimum in the evening. Another effect is concerned with lung diseases. The coal miners being given certain doses of ultraviolet light every day is based on the theory of the radiation providing protection against lung disease.

UNDERSEA MUSEUMS

Throughout the US there are many campgrounds that the Department of the Interior of the federal government has estab­lished at places of historic or scenic interest. Those at Yellowstone Park, the Grand Canyon, or the battlefield at Gettysburg, Pennsyl­vania are examples. These camping places have become more and more crowded during the last few years as an increasing number of families take their vacations by car. Until recently, however, no one had thought of using the resources of the underwater areas off the coasts as recreation areas. Now since scuba diving has be­come so popular, four undersea areas have been set aside as re­treats for swimmers and divers who want to get away from the crowds found in most vacation areas.

The explorations of the French oceanographer Jacques Cousteau and his son Philippe brought to world attention the ships and planes that were wrecked off Truk Island in Micronesia in World War II. In 1972 the US government declared this area a national monument. Since then, many adventurous scuba divers have been able to explore the hulks of some seventy sunken ships in a park that is both eerie and fascinating.

More recently, the US government has established Buck Is­land Reef National Monument just off St. Croix in the Virgin Is­lands, and has set up underwater markers to identify the coral. The government has even put up picture markers giving the names and habits of the fish.

The first subsurface park in the continental United States was established at Key Largo, Florida. It covers some seventy-five square miles, and gives the diver his only chance to see living coral in North American waters. Since then more than three million people have enjoyed the many types of coral on the reef and the varieties of fish that go swimming by.

Another undersea museum has recently been set aside at Big Sur, California. It adjoins a park area along the shore.

Since the appearance of scuba in 1943, adventurers under the sea have shown that they can venture almost anywhere. Perhaps in the future the sea will have become nearly the only place where man can retire to find the solitude he once found in the vast empty areas of the land.

(scuba - сокр. self-contained underwater breathing apparatus)

Water.

Part I. The properties of Water.

Water really is a substance number 1 in our life. H₂O! One atom of oxygen plus two atoms of hydrogen. Probably one of the first chemical formulas you ever learn. It is difficult to imagine life without water. That is why people attribute magic properties to water and call it the "water of life" or life-giving water.

Water is the great fraud. There are 3 phases of water: ice, liquid and gas. It boils at 100°C and freezes at 0°C. There are many admixtures in the water and they change its properties. Water molecular is polar.

There are 3 isotopes of hydrogen: protium (H₂O), deuterium (D₂0). tritium (T₂O). They could be mixed together. For example an atom of protium and an atom of deuterium (HDO). There are also 3 isotopes of oxygen: oxygen-16, oxygen-17. oxygen-18. Taking into account these varieties of oxygen and hydrogen there are 12 kinds of water. These waters have different densities and different freezing and boiling points. Deuterium is also called the heavy water and it is used in nuclear reactors for moderating neutrons which cause uranium fission.

Water is the greatest chemist in the world. No natural process takes place without it - be it the formation of a new mineral or a highly complicated biochemical reaction taking place in the organism of a plant and an animal. For instance in photosynthesis, in transport (osmosis and osmotic pressure), in reproduction. There is no rock on the earth that can resist the destructive action of the water.

(deuterium - дейтерий, тяжелый водород; protium - протий, легкий, обычный водород )

Part II. The Water cycle.

The Earth's supply of water is stable and is used over and over again. Most of the water (98%) is present in oceans, lakes and streams. Of the remaining 2 %, some frozen in the polar ice and glaciers; some is found in the soil, some is in the atmosphere as water vapor and some is in the bodies of living organisms.

Sunshine evaporates water from the oceans, lakes and streams, from the moist soil surface and from the bodies of living organisms, drawing the water back up into the atmosphere, from which it falls again as rain. Evaporation exceeds precipitation over the oceans, resulting in a net movement of water vapor, carried by wind, from the ocean to the land. Over 90% of the water lost on the land is by plant transpiration (evaporation of water from the soil plus transpiration from plants is called evapotranspiration). This constant movement of water from the earth into the atmosphere and back again is known as the water cycle. The water cycle is driven by solar energy.

Part III. The Water pollution.

The volume of both industrial and domestic waste has increased dramatically over the 50 years. Water pollution from industry can occur intentionally, when factories discharge their effluents directly into rivers, lakes, oceans, or when accidents cause leakage of toxic waste into the water supply. Dioxin presents in bleached paper products such as disposable diapers, toilet paper and coffee filters. Another pollutant waste of water is oil. Some of it comes from accidents, some from deliberate washing of tanks at sea and some from industrial effluents. Oil coasts the feathers of the sea birds and the scales of fish. It also reduces the level of oxygen dissolved in the water. Acid rain is another important cause of water pollution. It destructs the aquatic life and it is influence on fish and other living organisms. They become toxic. Another cause is thermal pollution. Industries which used water for cooling increase the temperature of nearby rivers and lakes by 5-10 degrees. In addition, together with domestic sewage and artificial fertilizers, it promotes overgrowth of bacteria and algae by eutraphication and disrupts the aquatic ecosystem.