STAINING REAGENTS. 75 



Safranin is specially used as a nuclear stain, and very largely for 

 the study of mitosis. It is specially useful for tissues hardened in 

 Flemming's mixture. 



Safranin ..... I gram. 



Absolute alcohol .... 100 cc. 



Water ...... 200 ,, 



It may also be used as a much stronger alcoholic solution, 5 per 

 cent, in 70 per cent, alcohol. There are several varieties of this 

 dye, and some of them are of little value as dyes. Therefore it is 

 important to obtain a good sample. That sold as safranin-O can 

 usually be relied upon, and is to be obtained from Dr. George 

 ( Iriibler, Leipzig. 



In using this dye, the sections are, as a rule, left for several 

 hours in the solution even twenty-four hours or longer and ;uv. 

 then placed in ordinary alcohol or acid alcohol (p. 65) containing 

 .5 per cent, hydrochloric acid to remove the surplus stain. If this 

 be properly done, the nuclei the chromatin of the nuclei only are 

 stained. Sections may be mounted in balsam. 



Application. 



(1.) Stain sections in i per cent, watery solution of safranin 



(1-24 hours). 



(2.) Wash rapidly in water. 

 (3.) Wash in absolute alcohol or acid alcohol. 

 (4.) Absolute alcohol, oil, balsam. 



Sometimes it is useful to use it in aniline-water, after Ehrlich's 

 method (p. 73). 



As shown by Martinotti, it colours black or dark-purple elastic 

 fibres hardened in 0.2 per cent, chromic acid (Lesson X.). 



(E.) Brown Aniline Colours. 



Bismarck Brown or Phenylene Brown. This is but slightly 

 soluble in water, but it forms a good ground-stain in contrast to 

 htematoxylin, and is useful for staining plasma cells and the cells of 

 the cerebrum. It preserves its colour when mounted in Farrant's 

 solution or balsam. 



((/.) Boil Bismarck brown with 100 of water ( = 3-4 per cent.). 

 Filter and add one-third its volume of absolute alcohol. 



(/>.) Or use a concentrated alcoholic solution in 40 per cent, 

 alcohol ( = 2-2 i per cent.). 



Application." 



(1.) Stain (5 minutes). 



(2.) Wash out in strong spirit. 



(3.) Alcohol, oil, balsam. 



It does not tend to over-stain. It is a nuclear stain, and the nuclei 



