Microscope Activities, 35: Posture at the Microscope
EXPERIMENT 35: Posture at the Microscope
To become aware of the need for correct posture when using a microscope, especially for extended time periods, so as to avoid back and neck pain.
Observations through the microscope often involve a considerable expenditure of time, especially when making drawings of microscopic specimens, or when constant, uninterrupted observation is required for working out life histories of micro-organisms. For this reason, it is imperative that the microscope user be comfortable when using the microscope. The configuration of the microscope partly determines the positioning of the use; that is, whether the instrument being used is an upright, vertical monocular or binocular microscope, or an inclined monocular or binocular microscope. The selection of a chair and workbench height are other considerations in establishing correct posture when using a microscope.
Posture When Using an Upright, Vertical Microscope While Standing
The worst possible position when using an upright, vertical microscope— or any microscope, for that matter—is standing! Figure 35-1 illustrates a student using an upright, vertical monocular microscope while standing. Here, the microscope is being used at a demonstration table that is too high to use in a sitting position. The upright, vertical monocular microscope in use on such a high bench requires the student user to remain standing, but to be bent over, resulting in strain in the lower back. The student is attempting to relieve the strain by using his right hand to push against the table, and supporting his head with his left hand, with elbow on the table—a kind of tripod position. This may be fine for a brief observation, but is totally unacceptable for extended use; standing use of the microscope should be avoided!
Posture When Using an Upright, Vertical Microscope While Sitting
All microscope use should be done from a sitting position; however, the table height, design of the chair, and height and design of the microscope all factor into comfort. For the most part, ordinary tables and desks of 30-32 inch height are employed for microscope work, accompanied by ordinary chairs of fixed height; Figure 35-2 illustrates a common example.
Here, at least the young man’s back is straight, but as the upright, vertical monocular microscope is still too high, he has inclined the microscope for comfortable use; daylight is being used as the light source. This seated position is fine, as long as the micro slide specimens are permanent preparations; if fresh liquid mounts are used the microscope stage will have to remain horizontal, and the student will have to add a seat cushion or two to his chair to allow him to look into the microscope, and still be comfortable.
Note that the microscope being used here is the “Continental”, or “6 inch” (160 mm) tube length. The older “English” or “10 inch” (250 mm) tube length cannot be used on an ordinary table or desk, unless it is inclined to an almost horizontal position. The Reverend Dallinger, who revised and largely rewrote Carpenter’s The Microscope, made a microscope stand for himself to use such a 10 inch microscope that was about the height of a foot stool so that he could use his microscope while seated in an ordinary chair! As for the use of daylight as a light source, that too is fine for general use, as long as it is from a window that faces North—which is a general guideline for artists as well, working in the Northern Hemisphere; sunlight must never be used to illuminate microscope specimens because of the danger of eye damage or permanent blindness.
Many schools have tables much lower than 30- 32 inches for the use of very young students, and these are often scalloped so that four students may be seated on fixed-height stools, and all use a single chalet-type light source in the middle of the table; many science and biology classrooms have similar table/stool arrangements.
A very useful microscope bench for individual use whose design goes back to at least 1914 is illustrated in Figure 35-3. The unique feature of this work table, originally designed for chemical microscopy, is the semi-circular cut-out; this work table is used with a stool adjustable in height and provided with a swivel seat. The advantage of this indentation or cut-out portion is that it allows the user, sitting well up into the cut-out, secure support for their arms, and enables them to sit up straighter, resulting in far less fatigue during long observation and manipulations. Furthermore, the compound microscope may be placed to one side of the cut-out, so that the other side may be used as a preparation area, or for a stereomicroscope. A shelf was later placed at the rear of the work table. Rows of long tables with these semicircular cut-outs, all facing windows, were used in the chemical microscopy classes at Cornell University for many decades; these tables had a height of 27 3/8 inches. Figure 35-4 illustrates a professional use design of this microscope table together with dimensions which Fisher Scientifics’ Contempra Furniture Division made until just a few years ago.
Posture When Using an Inclined Microscope While Sitting
Modern professional-grade microscopes are generally designed to be modular; that is, their “infinity” design allows for the stacking of various specialized modules, such as vertical illuminators (for polished metals, ores, materials, composites, and other opaque specimens), Bertrand lens units (for polarizing microscopes), epi-fluorescence units (for ultra-violet excitation), and infrared units (for obtaining IR spectra). Just adding two such modules to the basic microscope makes for a very tall microscope assembly whose eyepieces end up being 21 inches or more above the table; on an ordinary table of 30–32 inch height, this results in the eyepieces being more than 5 feet above the floor! To use these kinds of microscopes, very tall, fully-adjustable laboratory seats are required to accommodate all users. Some manufacturers try to alleviate the situation by providing specialized tiltable binocular heads whose inclination may be varied from about 30° to 90°. At Hooke College of Applied Sciences, where such elaborate professional microscopes with fixed-incline eyepieces ~21 inches above the table top are used, both the tables and the chairs are fully adjustable for height.
Student-grade microscopes used in most schools are of a more modest, conventional height; however, this can cause just as many problems. Figure 35-5 illustrates an inclined monocular Motic microscope as used in the first two Microscopy Workshops offered to middle and high school teachers of science. In this particular illustrated case, the adjustable chair has been lowered to minimum height, yet this average-size student has to bend into an awkward, uncomfortable position that is certain to result in severe back and neck pain. This is a very common occurrence in many schools, and is compounded if fixed-height stools are being used. The solution to this problem, although an easy fix, is seldom utilized; all that is needed is to take the time to raise the microscope using boards or boxes or books, as illustrated in Figure 35-6.
The student—who, you will have noticed, is left-eye dominant—is now in a comfortable, upright position, and prepared to make microscopical observations for extended periods of time without fatigue. A few microscope manufacturers of such inclined instruments design the microscope’s carrying/storage case in such a way that it can be used as an elevating platform. One glance around the classroom will quickly indicate which students require chair height adjustment, or elevation of the entire instrument.
The classroom teacher needs also to be aware of the special needs of handicapped students who are wheelchair bound. The bottom of the bench top should, ideally, pass over the arm rests of the wheelchair. When taller microscopes are in use, it may be necessary to fashion a workbench top that spans the wheelchair arm rests.
Whatever the situation, the point is that the table top, chair height, and any additional microscope platform needed, all need to be arranged so that the microscope user is sitting straight up and in a comfortable position for extended viewing.
Following the procedures outlined in the Discussion section, arrange your table, chair, and microscope in such a way that you are sitting upright, without stretch or strain, and that you feel comfortable. Look around the classroom, and make certain that each student is in a similar optimally comfortable position.