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A microscope slide and a coverslip (cover glass) are all that is needed for an examination of pond water using a slide microscope. For the beginning and intermediate observer any microscope slide and coverslip will work. There are specialized slides which are optically flat or specially treated for tissue adhesion for the professional microscopist. For beginners or teachers prepared slides are a good introduction to the types of things which are studied using a microscope. The Meade #9o4 25 piece prepared slide kit has a good sampling of various types of plant and animal tissues. If you are interested in a particular line of study such as cell reproduction and development or human and animal parasites the Konus prepared slides will help the student or the teacher focus on the subject. If you are buying a microscope for the student for the first time, remember the blank slides, the cover glasses; and some prepared slides for instant observation.

The world of microscopes and the science of microscopy date from the 1600's. Microscopy has fascinated man from the first realization that small objects could be magnified and examined in minute detail. The "homonculus" was thought to be a complete being contained within a human germ cell as early as the 17th century and needed only the time to grow and mature to become a recognizable being. The search for homonculi may have been the earliest inspiration for the development of the modern compound microscope. So where can one go to learn about the development of microscopes and the art and science of microscopy? Fortunately that question is easily answered and resources abound with information from the most basic to the most advanced. A number of major microscope manufacturers sponsor well annotated and well documented web sites and while these may be a little biased in the instruments that are featured the information is nonetheless invaluable. Some of the best include MicroscopyU sponsored by Nikon, the Zeiss site and the Olympus site. So when you decide to enter this fascinating world and invest in a microscope, do some homework, get some basic knowledge and explore the microuniverse around us. Make an informed purchase at a price point you can afford. You may not discover a homonculus or an animolecule, but you are sure to be amazed by what is invisible to the unaided eye.

So your student needs a microscope for high school biology class. If the student is looking at slides they will need a compound light microscope. There are 3 important things to look for. The first is good optics. With optics in microscopes you get what you pay for. A microscope with plastic parts and lots of magnification will be frustrating to the student. The second thing to look for is coarse and fine focus. At higher magnifications the student must have fine focus. The last thing is illumination. A mirror for illumination will not be sufficient for High School work. A light and a condenser to focus the light are essential for viewing the objects on the slides. Notice I did not say high magnification was important. Be wary of microscopes claiming 1500X - this level of magnification is not easily obtained even by the most sophisticated microscopes. 400X is sufficient for high school biology work. A good extra to make their work easier would be a mechanical stage.

One of the characteristics of a microscope eyepiece is the microscopic field of view commonly abbreviated FOV. The size of the FOV is expressed numerically in millimeters and is directly proportional to the combination of the eyepiece and the objective in use. The eyepiece, also referred to as an ocular, has a field stop as part of its design. The FOV is limited by this field stop and is defined as the diameter of the circle of light seen when looking into a microscope. The actual FOV is calculated by dividing the field number (FN) by the objective magnification. An eyepiece with FN=20 used with a 10X objective would have an FOV of 2.0 mm while an eyepiece where FN=26 would have an FOV of 2.6 mm. Widefield oculars have the advantage of showing a larger area of the sample at a given total magnification. Stereoscopic microscopes tend to offer a larger FOV even though their total magnification capabilities are less than compound microscope.

Leukocytes or white blood cells are the key component of the human body's immune system and on the first line of defense to protect the body against pathogens and foreign material. White blood cells are divided into three classes: granulocytes, lymphocyte and monocyte. Granulocytes get their names from the granules found within their cytoplasm. Granulocytes make up at least half of the leukocytes within the human body. They are divided into three sub-classes: neutrophils, eosinophils and basophils. Neutrophils is the most common type of leukocyte within the body producing trillions per day within your bone marrow. These cells are in constant reproduction because their life span is less than a day. Neutrophils are most attracted to foreign material, bacteria and inflammation. Upon siting a foreign invader the neutrophils will engulf it and use enzymes and other chemicals from its granules to kill it. If there is a surplus of neutrophils clustered at a site to kill a foreign invader pus will form. Eosinophils, a less common white blood cell, is attracted to parasites in the skin and lungs. While Basophils is attracted to inflammation and carries histamine. When histamine is "over" produced within the human body it causes allergies. Lymphocytes are the second largest class of white blood cells They are divided into two classes: B and T. B-Cells mature in bone marrow and mature into plasma. B cells are attracted to pathogens and form antibodies. Once a pathogen is sited, B cells clone themselves to produce antibodies to fight off the pathogen. T-Cells mature in the thymus gland. T-cells can detect cells within the body that are carrying viruses and kill them. Monocytes mature into macrophages by floating in the bloodstream and entering tissue. They are the largest, in size, white blood cell within the body. Most organs in the body have their own macrophage. The macrophages found within the lungs for example ingest dust, particles, and bacteria. They are also responsible for clean-up of other white blood cells, such as pus. For more information regarding the leukocytes and the immune system please visit: http://health.discovery.com/