5. Wash, for one minute in— 
Water ----- 50 c.c. 
Pot. permanganate, 1 % solution 2 drops. 
6. Wash in water five minutes. 
7. Stain with Romanowsky. 
For Breinl’s method, which is more complicated, 
vide Annals of Tropical Medicine and Parasitology , 
Vol. I, No. 3. 
To Measure Objects 
Method /.—It is necessary to have (a) a scale 
which is put into the eyepiece, and ( b ) a slide with a 
millimetre (divided into hundredths) scale ruled on it. 
Unscrew the top of the eyepiece and place scale {a) 
inside, place the top on, and by holding the eyepiece 
up to the eye see if the scale is in focus; if not, shift the 
diaphragm on which it rests up or down until it is so. 
Now focus scale ( h ) placed on the stage. Both scales will 
now be seen at the same time. Proceed then to find 
out how many divisions of the stage scale ( b ) one 
hundred, or fifty (or any smaller number) divisions 
of the eyepiece scale {a) cover. Let us suppose we 
find that forty divisions of the scale ( a) cover eight 
divisions, i.e . 9 tui> mm., i.e ., 80/*. Therefore one 
division of the scale (a) is equal to 2^. Then knowing 
this—leaving the eyepiece scale in position and removing 
the stage micrometer—let us now measure a blood cell, 
and let us suppose we find it covers (using the same 
lens and eyepiece as before) three divisions. As we know 
that one division measures 2/^, the blood cell measures 
6 ^. Having once determined the value of the eye¬ 
piece scale for each combination of lenses and a definite 
tube length (16a mm.), we require scale ( h ) no longer. 
We simply place the scale (a) in the eyepiece, determine 
