Microscope Usage Observing Tips

Written by microscopes

Monday, 03 September 2007

Microscope Usage & Observing Tips

Sometimes the worker may have faithfully carried out all the directions heretofore given and been assured that his lenses possess the above named qualities as they ought, yet be unable to obtain the desired results. He may be working with a water mount and his dry objective become "immersed" in some water which has worked to the top of the cover glass. His objective may be dirty from a previous "immersion," or it may have some other dirt upon the front lens. The field may be covered with specks which revolve when the ocular is turned. The field may be dim or hazy, due to dirt on the back of the objective or a film on the inner surfaces of the lenses of the ocular, or because of moisture settling on the lenses because they have just been brought from a cold into a warm room. He may see great streaks on his field, which are due to his own eye lashes, or he may see small, slowly moving bodies floating across the field. With the exception of this last, the ailment has only to be mentioned to suggest the remedy. The muscae volitantes, as these last named bodies are called, are little specks or shreds in the vitreous humor of the eye which cannot be removed, but which can easily be disregarded.

In water mounts and fresh balsam mounts one is apt to find air bubbles. To be sure, that the object is an air bubble, focus up with central light. The bright spot in the center will become clearer while the edge will become darker. With oblique light the bright spot will be thrown to one side. In studying water, blood or any fluid, always cover the drop with a cover glass. The objectives are corrected for rays passing through media with parallel surfaces. If such a mount is not kept horizontal, currents will be set up, due to gravitation, and they will be seen with a magnified velocity seemingly running up hill.

The fact that the microscope reverses every movement and magnifies it may be mentioned again.

Beside any movement due to currents there is sometimes a peculiar indefinite to and fro movement of particles from one position to another. This is called Brownian movement.

In studying sections a true idea of the structure of the tissue can only be obtained by moving the slide about to bring different parts into the optical axis and by focusing with the fine adjustment to bring different levels, or optical planes, successively into view. Where serial sections are used each section must be studied in relation to its neighbors.

Sometimes sections which are freshly mounted in balsam appear cloudy and indistinct. This is because of failure to thoroughly dehydrate the specimen before putting it into the balsam.