3

films are fixed by immersion from ten minutes to half an hour in absolute
alcohol. For this and for staining purposes the glass stain-pots shown in Fig. 3

[NLS note: a graphic appears here - see image of 75022381.tif]

Fig. 3.

will be found very useful. A large number of slides can be fixed in one of these pots
at the same time; but before placing each slide in the alcohol, a number by which
it will be known should be written upon it with Indian ink or a "glass pencil."

      For staining blood films we have usually employed either alcoholic hæma-
tin or Romanowsky's stain, and other stains than these are seldom necessary.

      The alcoholic hæmatin stain possesses the advantages of being very
easily worked, of being permanent, and of showing up the pigment in malaria
parasites better than Romanowsky's stain. With a little practice, however,
very beautiful results can be obtained by Romanowsky's method, and as, in a
slide stained by this method, it is almost impossible to overlook even the smallest
ring forms, it is to be recommended even for routine work.

      The alcoholic hæmatin stain is made as follows :*—

      The fixed and dried films are left in this solution for from ten to twenty
minutes or longer, until the blood film has a faint brown hue. They are then
washed in water, allowed to dry in the air, and examined with the oil-immer-
sion lens without applying a cover-glass. The parasites show clearly against
the grey brown colour of the red cells.

      Romanowsky's stain is made as follows :—

      Stock solution, A :—

      Grind up the methylene blue in a pestle and mortar and add it gradually to
the water. When the solution has been made, add the sodium carbonate.

      * Reports to the Malaria Committee of the Royal Society, 3rd Series, Stephens and Christophers
"The Malarial Fevers of British Central Africa."

B 2