i8 
MAMMALIAN ANATOMY 
6. Place upon the stage the slide upon which the preparation 
to be studied has been mounted (see p.19 ) with this preparation 
itself over the center of the aperture of the stage. 
7. Focus with the low power. Before doing this, lower the 
microscope tube, if necessary, by means of the coarse adjustment, 
until the lower end of the objective is about an eighth of an inch 
above the slide, watching the process carefully to see that the 
objective does not come in contact with the slide. Never lower 
the coarse adjustment while looking through the tube. Then, 
looking through the tube, with both eyes open, slowly raise the 
tube by means of the coarse adjustment until the outlines and 
details of the object can be sharply seen, the indication that the 
microscope is in focus. The focus may now be sharpened, and 
different levels of the object may be brought out by use of the 
fine adjustment. Never try to see what is not in focus. 
8. If a certain region is to be studied with greater detail, 
change from the low to the high power. In case the 
microscope you are using is parfocal, the following method 
should be used: 
With the low power objective in place, focus the microscope 
upon the object to be studied. Looking through the microscope, 
move the slide so as to bring into the middle of the field the detail 
which is to be studied under high power. Without changing the 
adjustments, turn the revolving nosepiece so as to bring the high- 
power objective into line with the microscope tube. A slight 
turning of the fine adjustment should now suffice to bring the 
object sharply into focus. In most microscopes the change from 
low to high power involves a slight downward focusing with the 
fine adjustment, but you should determine which direction is 
necessary with each instrument that you use by cautious experi¬ 
ment, while looking through the tube to see when the focus is 
sharp. Never use the coarse adjustment with the high power, 
but if the microscope gets out of focus turn back to the low power 
and start over again with the coarse adjustment. 
9. Remember that the microscope is an aid to vision, and if 
used properly with both eyes open and used alternately, and with 
frequent resting for a moment by looking off at some distant object, 
the microscope will never injure the eyesight. 
