88 The Preparation of Microscope Slides 



ing, stain a test slide. If the cytoplasm is colored, mix in a few more drops 

 of acid and test again; continue until the critical point is reached. Usually 

 about 1.8 ml of acid is required. 



Method for Sections 



1. Accumulate slides in water. 



2. Place in stain from 1 to 5 min. The time is not critical since over- 

 staining cannot occur. 



3. Rinse in water, dehydrate, clear, and mount in balsam. 



Safranin. Safranin nuclear staining in English-speaking countries is 

 usually confined to botanical specimens, though its use in European 

 countries is widespread for histological purposes. Safranin is not easy 

 to use and is a very slow stain. Undoubtedly the best method is: 



Note: Dissolve the dye in the methyl cellosolve. Then add the alcohol. 

 Dissolve the sodium acetate in the formaldehyde and water and add these 

 to the dye solution. 



Differentiating solution 



Identical with that used with Regaud's hematoxylin (see page 81). 



Method for Plant Sections 



1. Accumulate slides in 70% alcohol. 



2. Stain for 1 to 3 days. 



3. Differentiate until nuclei and xylem are sharply defined. 



Stain Is Used on Animal Tissues as Follows: 



1. Accumulate the sections in water. 



2. Transfer the sections to stain and let them remain there from 24 to 

 48 hr (or even longer) until the nuclei are darkly stained. 



3. Dip the slide up and down in the differentiating solution until the 

 unwanted stain has been removed from the cytoplasm. 



4. Wash it in running water to remove the picric acid. 



5. Mount the section in the usual manner. 



