THE MICROSCOPELEARNING OBJECTIVE:Identify theparts of the microscope, and determine theirfunctions.Before any attempts are made to view bloodsmears, urinary sediments, bacteria, parasites, etc., it isabsolutely essential that beginners know theinstrument with which they will be spendingconsiderable time—the microscope. The microscopeis a precision instrument used extensively in clinicallaboratories to make visible objects too small to beseen by the unaided eye. Most laboratories areequipped with binocular (two-eyepiece) microscopes,but monocular microscopes are also commonly used.The type of microscope most often used in thelaboratory is referred to as the compound microscope.See figure 7-5. A compound microscope contains asystem of lenses of sufficient magnification andresolving power (ability to show, separate, anddistinguish) so that small elements lying close togetherin a specimen appear larger and distinctly separated. Inthe following sections, the compound microscope’sframework, illumination system, magnificationsystem, and focusing system will be discussed.FRAMEWORKThe framework of the compound microscopeconsists of four parts: the arm, the stage, themechanical stage, and the base (fig. 7-5).ArmThe arm is the structure that supports themagnification and focusing system. It is the handle bywhich the microscope is carried.StageThe stage is the platform on which a specimen isplaced for examination. In the center of the stage is anaperture or hole that allows the passage of light fromthe condenser.7-7EYEPIECESBODY TUBEARMMECHANICAL STAGECOARSE CONTROL KNOBFINE CONTROL KNOBBASEINTERNALLIGHT SOURCECONDENSERIRIS DIAPHRAGMSTAGEOBJECTIVESREVOLVINGNOSEPIECEHM3f0705Figure 7-5.—Compound microscope.
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