The Microscope
The microscope is an invaluable tool to a biologist. Why, you might ask? Microscopes, of course, are tools that magnify minute objects that could not otherwise be seen or well defined to the naked eye. There are a few different types of microscopes. The major types are the electron microscope, (1.e. the scanning electron microscope or the transmission electron microscope.) the scanning probe microscope (which generates images based on touch-sensitive contour) and the scanning acoustic microsope (which uses sound vibrations.1)However, the most common type of microscope is the optical microscope. These microscopes use light concentrated through lenses to magnify an object. The two types of optical microscopes are the dissection and the compound. The latter is the one I have learned to use today.
The compound: a brief history
In 1595 in Middleburg, Holland lenses were placed at either end of a simple middle tube. Thus, the compound microscope was born. Who actually created it is a debatable mystery. It is accredited to Zacharias Janssen. However, when this first microscope was invented Zacharias was very young and for this reason it is thought that his father, Hans, actually invented the compound microscope. Both were eyeglass makers by trade and it wasn't long before Zacharias began production on the microscope.
This primitive form of the microscope was later improved upon by Robert Hooke, a Brittish scientist and inventor. Through a slightly more powerful microscope, Hooke viewed the microscopic structure of a cork and, thus, coined the term "cells" describing the porous pockets in the cork. This was published in "Micrographia" in 1665. This publication inspired a vast improvement on microscopes and the discovery of microscopic organisms living in water. These were made by Anton Van Leeunwenhoek only 9 years later!
Leeunwenhoek first dealt with magnification when improving on magnifying glasses that were used in the dry goods store that he worked in. After producing the finest lenses of his time, he put them to work in building microscopes. These became known as the first practical microscopes. With them he not only saw microscopic life in water, but also blood corpuscles in circulation and bacteria.
Since then the compound microscope has made leaps and bounds, but the principle is the same, one that we have used for 400 years.
The compound microscope, practically speaking
There are many parts of the microscope to become familiar with in order to operate it. The eyepiece and body tube are, naturally, what you look through to observe an object. The stage is where the specimen sits. The specimen in viewe through the opening on the stage called the aperture. It is held in place by the stage clips. The course focus is just that. It moves the stage at great intervals. The fine focus is more exact. The light source will illuminate the specimen. The diaphragm is for adjusting the amount of light that comes to the specimen. The stage controls or x and y knobs move the stage horizontally to center the specimen. The nosepiece holds the objective lenses and makes them rotatable. The objective lenes determine how much magnification will be used for a viewing a specimen. With a clear knowledge of these one can begin to observe microscopic specimens
Using the microscope simulator I was able to learn to use all of these properly. I also learned how to adjust the oculars (eyepiece for viewing) so that the specimen could be properly observed. W
hen observing a specimen at varying magnifications there are naturally going to be some modifications of focus and lighting. It seems to me that the larger an object is magnified, the more light it needs. This is taken care of by opening, more, the diaphragm. The reverse is true for less magnified object. The image to the right shows a cheek smear sample at 40x magnification. The iris diaphragm is opened just about half way. For an object maginified 100x the diaphragm on the virtual microscope is fully open. From there you can fine tune the focus with, of course, the fine focus to get the best view of a specimen that you can.
hen observing a specimen at varying magnifications there are naturally going to be some modifications of focus and lighting. It seems to me that the larger an object is magnified, the more light it needs. This is taken care of by opening, more, the diaphragm. The reverse is true for less magnified object. The image to the right shows a cheek smear sample at 40x magnification. The iris diaphragm is opened just about half way. For an object maginified 100x the diaphragm on the virtual microscope is fully open. From there you can fine tune the focus with, of course, the fine focus to get the best view of a specimen that you can.If only: the online plight
Studying human biology online has it's obvious drawbacks. The first one I have encountered was that I won't be using a real microscope to often, if ever, for this course. It was, still, a very valuable lesson to be learned. I am glad that I now know how to use the compound microscope and have indulged my historical fancy with a brief lesson in where the microscope came from. An invaluable tool, to be certain, I cannot wait until my studies bring me to the microscope and the rush of discovery.
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