|
Setting Up the Light Microscope.
Setting Up the Light Microscope
When an object is to be examined, the microscope is placed near a window, or, if at night, near a lamp of some sort from which light may be picked up by the mirror and reflected up through the object. The tube is inclined at a convenient angle and the mirror is manipulated until the light is reflected upon the slide where it may be seen. The eye is then applied to the eyepiece and the illumination examined. It will probably be imperfect or unevenly distributed, in which case the mirror must be adjusted until the entire field is illuminated. Now remove the eyepiece from the tube (if this is so arranged that it may be done without unscrewing it) and examine the little spot of light which appears upon the rear lens of the objective. If this spot is not in the exact center of the lens, shift the mirror until it is, for this is the position for the best illumination. The secret of securing this condition lies in picking up the light in the center of the mirror. If artificial light is used, move the illuminator until the image of the bulb or other ilium inant is in the exact center of the mirror, then direct the light upwards through the stage opening into the microscope. Now lower the tube, focus upward until sharp focus is secured and the examination may proceed. Many objects may be examined in a dry state simply by placing them on a slide for viewing. Others, such as the minute organisms found in pond water, may be examined only in their natural state, for as yet no method has been discovered or invented for mounting many of them. Other subjects require preparation for mounting, either by washing, slicing, decoloring, softening, staining or any one or combination of several processes. Indeed, the preparation of the collected material is just as fascinating as the examination of the prepared slides, and the student should take pains at the very start to learn the correct ways of preparing material for examination. This preparation by the student is not only desirable, but really necessary if he wishes to learn something of the wonders of nature. Dealers' lists contain large numbers of slides ready made, but for the student to purchase a slide containing the foot of a fly is foolish and extravagant. If he lives in some inaccessible place and has no idea what a slide is he might buy one to show what is to be aimed at in preparation, but for no other reason. Certain very rare slides may be purchased but there are so many thousands of subjects waiting to be taken home and mounted that he could fill his days for a year and do no more than scratch the surface. Methods of preparation and mounting will be described later in the text. The student may begin at once his work of collecting a library of microscopic material.
Related Items:
|
Microscope Technique 
