(12)
Films prepared in this way should be allowed to dry in the air and then
fixed by immersion in absolute alcohol for ten minutes.
Siaining the
specimen.
It is better for the beginner to get accustomed to one stain than to
attempt many different methods, and the best stain for our present purposes
is that recommended by Romanowsky. This is a triple stain consisting of a
combination of a particular kind of eosin and medicinal methylene blue. A
modification of it called Leishman's stain can now be obtained in the form
of compressed tabloids * which are very convenient to use. Each tabloid
should be dissolved in 10 cubic centimetres of pure methyl alcohol, and the
stain is then ready. If this stain is used, previous fixation of the blood film is
unnecessary. After the film has dried in the air it is covered with a few drops
of the stain. A few seconds afterwards, and while the stain is still liquid, an
equal quantity of distilled water is added to the stain, and the slide is moved
about so as thoroughly to mix the water with the stain. This mixture is
allowed to remain on the film for from ten to twenty minutes, and is then
washed off with a stream of distilled water. The slide is then allowed to
dry in the air. It is not necessary to cover the film with a cover glass;
the oil for the oil-immersion lens may be placed directly on the film of
blood.
When it is desired to send specimens of blood for examination in a
laboratory dry films taken in the manner just described must be sent, but
they need not be fixed or stained ; each slide should be wrapped in a piece of
clean paper on which the particulars of the case are written.
Microscopic
examination.
When the making and preparing of blood specimens has been sufficiently
practised one will take up the task of microscopic examination. For this
purpose a good microscope provided with a one-twelfth inch oil-immersion
objective is necessary. We must commence our examinations not with
specimens of blood from patients in hospital but with specimens of ordinary
normal blood because "It is impossible to make reliable examinations of the
blood for malarial parasites without first being familiar with the ordinary
appearances of normal blood and the more common pathological changes."
* From Messrs. Burroughs, Wellcome & Co., London, and from many chemists in
India.
Lectures on the malarial fevers, by W. S. Thayer, M.D., Professor of Medicine in
the Johns Hopkins University.