Page 237 - Zoo Animal Learning and Training

Chapter 12 Laboratory Skills 221

condenser controls the amount of light refracted off of threading an objective in wrongly can ruin the entire
the mirrors inside the condenser. The iris directs the scope!
light into small or large areas. “Park” the microscope by turning the light source to
The light source control and power switch are on the its lowest setting, turn the power button off, point the
base. Depending on the manufacturer, these controls lowest objective toward the stage, lower the stage to its
are either on the side of the base itself, along the back of lowest position, and replace the cover over the micro-
the scope, or on the side of the arm of the base. The light scope. This may seem like a huge inconvenience but it is
source control knob or rheostat is used to make the light the best procedure for maintaining the microscope. If
brighter or softer. The power switch is of course to turn the microscope is in constant use during the day, the
the scope on and off. The light source located directly shutdown procedure can be done as one of the last
below the condenser houses the light bulb. These do things for the day. A very neglected scope can sometimes
burn out after a while and can be changed out by either be brought back to usefulness by a professional clean.
sliding the entire top of the light source away from the There are companies that travel to clean and fix micro-
scope or turning it upside down and accessing it from scopes. If you happen to have a college or university with
the bottom of the scope. Microscope light bulbs should a biology department in your area call them to find out
not be touched with bare fingers. The grease from our who they use and see if you can arrange for them to stop
hands will make the bulb get too hot and it results in it by the practice to clean your scope. It will save the clinic
burning out faster. Use a Kem Wipe or paper towel to money in the long run as a replacement scope can run
remove and replace the bulb. Before replacing the bulb up to $2000.
on a scope that won’t light up, check the power cord! It
has a habit of becoming loosened from the back of the
scope. This is especially true if the scope is slid back and Learning Exercise
forth on the countertop.
The microscope is often abused because no one takes Practice working with the microscope. If the school
the time to care and maintain it properly. If lucky enough has prepared slides, use one to find, focus, and
to find a manufacturer’s user manual read the instruc- move the slide. When scanning a slide you look at
tions for cleaning and maintenance of the microscope. the entire area under the coverslip. Practice this as
If not available, the following is routine care for the well because some people get motion sickness
microscope after each use. If taken care of well, this when they first start moving the slide.
piece of equipment will work forever. If not, it tends to
get filthy dirty and will no longer be useable.
The best possible care is to do a quick clean after each
use of the microscope. The sample slide is removed and Centrifuge
disposed of properly, usually in a sharps container. The
oculars are cleaned using a piece of lens paper with a Centrifuges (see Figure 4.24) are used to separate undis-
small drop of lens cleaner applied to one end of the solved solids from liquids, resulting in sample material
paper. Wipe the oculars off with the wet paper; if you that can be analyzed. Samples centrifuged in the labora-
have personnel that wears eyebrow pencil and mascara tory are clotted blood to obtain serum; unclotted blood
this is very important. The objectives are cleaned using to obtain plasma; urine to obtain sediment; and fecal
the other end of the same lens paper with another small solutions to obtain parasite ova.
drop of lens cleaner applied. Let both the oculars and There are four rules governing the use of every
objective air dry. If the 100× objective was used, the oil centrifuge.
should be removed after each use again with lens paper.
First wipe the 100× objective off and then apply a drop of 1. Always balance the centrifuge before turning it on.
lens cleaner to the lens paper and clean thoroughly. It An unbalanced centrifuge will “walk” itself off of the
never hurts to apply the same care to the 40× objective, counter. It will make a horrible racket and can break
as it is long enough to be dragged through the immersion or crack the test tubes, which will spin the sample all
oil by accident. over the inside of the centrifuge. In short, it makes a
If either objective has sat in oil for a while it may need terrible mess and can actually damage the
a deeper cleaning. This cleaning is accomplished using centrifuge.
lens paper and a small amount of alcohol, or xylene sub- 2. Always lock the lid especially on the hematocrit
stitute as needed. Immersion oil tends to become thick centrifuge. There are two lids: one to hold the
and somewhat crusty if left to dry on an objective lens. hematocrit tubes in place and one to cover the
The objectives can be turned out of the ring, but care spinning disc. Modern day centrifuges lock
must be taken when threading them back into place. automatically when they are started and unlock
The fittings are copper and bend easily so forcing or when the timer goes off. You can stop centrifuges