STAINS AND STAINING 23 



solve separately 0.8 Gm. of ammonium oxalate in 80 ml. of distilled 

 water. When both solutions are complete, add the oxalate solution to 

 the dye solution. 



The proportions used here are those given by Lillie. 



The use of this solution in staining bacterial films is described on page 100 

 and its use for the staining of nuclei is identical with the method outlined 

 for Ziehl above. 



Plasma or Contrast Stains 



Wholemounts are almost invariably stained in one color only since sufficient 

 nuclear stain usually remains dispersed throughout the plasma to provide 

 adequate visibility. The cytoplasm of sections, however, is usually stained a 

 contrasting color, both to render the nuclei more apparent and to emphasize 

 the general structure. Sometimes two or more colors may be employed. Single 

 contrasts are usually perfectly adequate, and the following may be recom- 

 mended: 



EosiN Y: 



Make up as a 0.5 per cent solution in distilled water. 



Ethyl Eosin: 



Make up as a 0.5 per cent solution in 95 per cent alcohol. 



Both these eosins give very much the same shade and are the conventional 

 contrast to hematoxylin- or celestin blue B-stained sections. The choice 

 between water and alcohol is a matter of individual preference. 



Another popular contrast stain is: 



Fast Green FCF: 



Make up as a 0.1 per cent solution in 90 per cent alcohol. 



This is sometimes used as a contrast for hematoxylin, for which purpose it 

 is not as satisfactory as the eosins, but it is very widely employed as a contrast 

 stain to red nuclei stained either with safranin or carmine. 



Double Contrast Stains 



It is no more trouble to use a single solution which will stain different 

 tissues various shades than it is to use a simple solution. Two solutions can 

 be confidently recommended. The first of these is: 



VAN Gibson's Stain: 

 Staining solution 

 To 100 ml. of a saturated solution of picric acid in water, add 0.05 Gm. 

 of acid fuchsin. 



STAIN IS USED AS FOLLOWS: 



1. Collect sections, with the nuclei stained blue, in tap water. 



2. Stain them from 2 to 5 minutes in the staining solution. 



