PROPHYLAXIS OF MALARIA. 
19 
trouble in securing a reliable stain, and, in time of active field opera¬ 
tions, if it were desired to issue the powder, it could be prepared in 
large amounts at the various department laboratories and issued in 
sealed glass tubes, each tube containing enough powder for a definite 
amount of staining solution, and with the powder could be sent 
enough of the proper methylic alcohol to make up the amount of solu¬ 
tion indicated. 
The powder used in preparing the staining solution is obtained as 
follows: In a flask add 0.5 gram of c. p. sodium bicarbonate to 100 
c. c. of distilled water; dissolve thoroughly, and slowly add, while 
shaking, 1 gram of Grubler's methylene blue; heat for one hour in 
an Arnold sterilizer after the steam is up, and then cool the solution. 
A considerable amount of the methvlene blue will remain undis- 
solved, but this should be allowed to remain in the solution. 
Make a solution of Grubler's yellow aqueous eosin by adding 1 
gram of eosin to 1,000 grams of distilled water. Add this slowly, 
while stirring, to the cooled methylene blue solution which has been 
poured into a white dish or bowl. The eosin solution is added until 
a well-marked precipitate appears and the surface of the mixture is 
covered with a greenish metallic scum. Test repeatedly, while add¬ 
ing the eosin solution, by placing a drop of the mixture upon a piece 
of white filter paper. When sufficient of the eosin solution has been 
added a well-marked pink halo should surround the small amount of 
blue precipitate left upon the paper. Now allow the mixture to stand 
for 15 minutes and then filter through one small filter paper; the 
precipitate is saved, dried in a hot-air oven at 60° C., the greenish 
mass thus obtained powdered, and stored in an air-tight bottle. Large 
amounts of the powder may be prepared by increasing the amounts 
of the reagents given, in proper ratio. 
The staining solution .—The solution used in staining the blood 
smears is prepared by taking 0.3 gram of the powder and adding it 
to 100 c. c. of pure methylic alcohol (this must be Merck’s reagent 
alcohol) filter, and add enough alcohol to bring the entire amount to 
the original 100 c. c. Let stand for an hour or two before using. 
Method of use .—Add a few drops of the staining solution to the 
blood smear and let stand for from three to five minutes. This fixes 
the specimen. Then add enough distilled water to cause a slight 
greenish metallic scum to form upon the surface of the solution; let 
stand for five minutes, wash in running distilled water, and examine 
when dry. The exact time for staining, after the addition of the 
distilled water, varies somewhat with different specimens of blood, 
but a little experience will soon enable one to judge the right time. 
The final washing with distilled water is very important, as by it 
the precipitate formed during the staining process is removed and 
the differentiation of the staining of the cytoplasm of the erythrocyte 
