THE DIAGNOSIS OF PROTOZOAN DISEASES 137 
Fixing the blood films. 1. By heat. (@) Open flame. Pass : 
the slide, specimen-side up, slowly through the flame of a Bun- 
sen burner until it is decidedly too hot for the hand to bear. At 
this temperature, which probably varies from 110° to 150°C., 
fixation is complete in from 1 to 2 minutes. Overheated slides 
can usually be seen to change color in the flame, after which 
the red cells stain yellow with eosin. A little practice will en- 
able one to tell when fixation is complete without overheating. 
(6) Ovens. Slides may be placed in an oven provided with 
a thermometer and exposed to a temperature of from 110° to 
150°C. from 5 to 10 minutes. 
2. By alcohol. Fix in from 95% to 97% alcohol from 
10 to 30 minutes. If left too long in alcohol they do not stain 
so well. For staining malarial parasites, fixation by alcohol 
is preferable. 
Method of using Nocht-Romanowsky’s stain. Put the stain 
in a Petri dish, place in it two or three toothpicks, matches 
with heads removed, or pieces- of small glass rod to support 
the slides, and place them, specimen-side down, in the stain 
upon this support. This allows any precipitate to settle away 
from rather than upon the slides. Allow the stain to act 1 or 
2hours. They will not overstain in 24 hours. Wash in water, 
and when dry they are ready to examine without a cover glass. 
Immersion oil can be applied directly to the films without injury. 
