SECTION TWO 



Sprinkle the PVA on the surface of the mixed liquids, then stir 

 for a few minutes with a glass rod. Heat, with constant stirring, 

 to 75°-8o° C. until the PVA has dissolved completely and the 

 solution is clear. 



Note: PVx\-fixative should keep for several months without 

 deterioration. 



B. 



Weigh out the dry components of the stain and place them in 

 a test tube. Add the acetic acid to the mixture in the test tube 

 and agitate. Allow the tube to stand for fifteen to twenty minutes, 

 then rinse it out with several lots of distilled water taken from 

 the 100 ml. already measured out. Pour the rinsings into a 250 ml. 

 flask and finally add the remainder of the distilled water. Shake 

 well. 



C. 90% alcohol . . . . . . 100 ml. 



Glacial acetic acid . . . . . . 0-5 ml. 



Technique: 



Note: Fresh specimens, faeces or other materials suspected of 

 containing protozoa are mixed with PVA-fixative. Immediately 

 or months later, permanently stained films can be prepared from 

 the preserved material. Microscope slide preparations are made 

 as follows: 



1. A drop of stool or other material (sigmoidoscocopic aspirates, 

 culture sediments, etc.) is placed on a slide and mixed with three 

 drops of PVA-fixative. 



2. Spread the mixture with an applicator stick (do not make 

 smears as in the case of blood) over about one-third of the area 

 of the slide. 



3. Allow the preparation to dry thoroughly overnight at room 

 temperature, or for at least three hours at 37° C. in the incubator. 



453 



