AGf~ICULTURAL RESEARCH, PUSA.

CHAPTER III
THE USE OF rrIlE MICROSCOPE IN
BACTERIOLOGY
MICROSCOPY is of primary importance in bacteriology,
and a suitable microscope and a knowledge of its use
are essential to those cngaged in bacteriological work.
To obtain satisfactory results, the microscope should
be used under the best possible conditions, and the
worker must know also the limitations of the instrument.
The component parts of the microscope are as
follows :-
'rhe eye-piece fits into a graduated draw-tube, which
in turn slides ill the body-tube. The lower end of the
tube is furnished with a revolving nose-piece (preferably
"triple "), into which are screwed the objectives. '1'he
tube and objectives are moved up and down by means
of a rack and pinion termed the coarse adJustment,
while the fine movements necessary for accurate
focussing are performed 'with the fine [u{jllslmcllt. The
tube and adjustments are supported by an -upright
which is connected to the foot by means of a hinged
joint. Attached to the upright neal' the joint is a
platform called the stage, 011 which is plaeed the microscopical
preparation to be examined. In the centre
of the stage is an aperture through which the object
can be illuminated from below. A mechanical stage
may be Httcd either to the stand or the fixed stage, so
that the preparation can be moved about horizontally,
thus ensuring steady and controlled movcment.
Below the stage !s the substage, which shoulcl be
furnished with a means of raising or lowcring-usually
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