Stains and Staining 91 



use a year after they have been prepared. To avoid these objections, the 

 author much prefers: 



Gray's Double-contrast Stain: 



Staining solution 



Water 100 ml 



Orange II 0.6 g 



Ponceau 2R 0.4 g 



Solution Is Used as Follows: 



1. Accumulate sections, with nuclei stained either in hematoxylin or in 

 celestine blue B, in tap water. 



2. Transfer the slides to the staining solution for 2 min. 



3. Remove each slide individually from the stain, drain, blot, and then 

 dip up and down in absolute alcohol until sufficiently differentiated. The 

 completion of differentiation and the completion of dehydration usually 

 coincide. 



4. Then transfer each slide to xylene and mount in the ordinary manner. 



This stain gives a good range of red-orange and gold shades on most 

 histological sections and is no more difficult to use than a simple solution 

 of eosin. 



Double-contrast stains for sections in which the nuclei have been 

 stained red are not very common, though the following, originally de- 

 signed for use with heavily yolked embryonic material, is really excellent. 



Smith's Picro-Spirit Blue: 



Staining solution 



Absolute alcohol 100 ml 



Picric acid 1 g 



Spirit blue Enough to saturate 



Stain Is Used as Follows: 



1. Take sections of material which have been bulk stained in carmine 

 through the ordinary procedures as far as absolute alcohol. 



2. Transfer them to the staining solution for 2 min and rinse individu- 

 ally in absolute alcohol until sufficiently differentiated. 



3. Then transfer the slides to xylene which stops further differentia- 

 tion. This gives good differentiation of a large number of tissues. On 

 embryonic material it is particularly effective, for the nuclei are red, yolk 

 and yolk granules are yellow-green to green, while yolk-free cytoplasm is 

 a clear blue. 



Complex Staining Techniques for Animal Tissues. Complex staining 

 solutions are those in which a series of stains, mordants, and differentiat- 



