cleaned in nonorganic detergents and rinsed well with distilled water. The etched
surface of the hemacytometer should be rinsed in water and blotted dry with lens paper
to avoid marring or further etching of the lines on the surfaces. A method of cleaning
small bore tubes and pipets (such as Wintrobe sedimentation rate tubes) is to attach a
capillary pipet, by a rubber hose, to a water type suction pump. Attach the tube to the
flat end of the pipet and hold the tube under water. Blood is drawn from the tube as
water is drawn in. When the tube is clean, invert the tube, remove the residual water by
suction, and allow to dry. Occasionally, the tube should be cleaned with dilute sodium
hypochlorite (household bleach) to remove deposits of residual blood.
Section III. LABORATORY EQUIPMENT
a. Introduction. A modern microscope for use in the hematology laboratory is
equipped with an illuminator system, a substage condenser system, an objective
system, a projector (eyepiece or ocular system), an iris diaphragm, nicol prisms, a
tubular barrel (monocular or binocular bodies), and a mechanical stage (see figure 2-5).
A compound microscope uses a combination of lenses, the objective lens (lens closer to
the object) and the ocular lens (lens closer to the eye) to project the image to the retina
of the eye. The objective lens acts much like a small projection lens which projects an
enlarged primary image near the top of the tubular barrel. This image, formed in air, is
known as an "aerial image". This object is viewed through the projector or eyepiece that
acts like a magnifier except that it magnifies an aerial object instead of an actual object.
The final image projected on the retina of the eye is called a "virtual image" because the
light rays appear to come from the image. The rays are actually created by an increase
in magnification by the lens system.
(1) Magnification in a microscope is limited to the useful magnification that
can be achieved, that is, the ability to obtain fine detail of the object being examined.
This ability to render visible the fine detail is the resolving power of the microscope. The
resolving power of a microscope is dependent on the numerical aperture (N.A.) of the
objective lens and condenser lens. Therefore, proper adjustment of these lenses is
essential in order to obtain useful magnification.
(2) Microscopes in general use in medical laboratories are provided with
three objectives with focal lengths of 1.9 mm, 4 mm, and 16 mm, respectively.
Microscopes are usually provided with 5X and 10X (most common) oculars. Multiplying
the power of the ocular by the power of the objective gives the degree of magnification
of the object under observation. The degree of magnification is expressed in diameters
(refers to an increase in diameter). The ocular magnification, the millimeter length of
the objective, its magnification power, and the total apparent increase obtained using
oculars and objectives of the powers shown are given: