92 
PRINCIPLES OP RACTERIOLOGY 
greatly in strength, and each one has to be tried out 
before it can be safely used) : 200 c.c. of 1 per cent solu¬ 
tion of methylene blue in 0.5 per cent solution of sodium 
bicarbonate in distilled water are steamed in Arnold’s 
sterilizer for one hour. 
Upon cooling, 1,000 c.c. of 0.1 per cent aqueous solu¬ 
tion of eosin (water soluble) is added, until a metallic 
scum appears on the surface of the mixture. The pre¬ 
cipitate which has been formed is collected by filtration, 
dried, and a satured solution is made in methyl (wood) 
alcohol. This is filtered and diluted with one-fourth its 
bulk of methyl alcohol. 
To look for malarial organisms, make a preparation 
in the same manner as for the study of blood, the so- 
called preparation for a differential count: clean the pa¬ 
tient’s ear or the tip of a finger with alcohol, dry and 
prick with a needle or a blood lancet; wipe away the 
first drop of blood, collect the next drop on a scrupulously 
clean glass slide; apply another slide, held at angle of 
about 45° so that the edge of the second slide just touches 
the first slide where the drop of blood is; this will 
cause the latter to spread, by capillary attraction, along 
the edge of the second slide; drag it along the first slide, 
holding it firmly against it, and you will get a thin, even 
“blood film.” This is allowed to dry, and the slide 
is then covered with the stain for one to two minutes 
(this does not stain but merely fixes the preparation be¬ 
cause of the methyl alcohol present in the stain). Now 
add a few drops of distilled water to the film covered 
with stain until a distinct metallic luster appears on the 
surface. Leave this on for five to ten minutes. Wash 
in distilled water and dry. 
In such a preparation the red blood cells appear pink 
(if they contain the malarial parasites the latter are seen 
