STAINING 743 



Application of the Hematein Stains. All of the above solutions 

 arc used in a similar manner. Sections, either free or attached to the 

 slide, are taken from water and immersed in the dye for three to five 

 minutes; they are then thoroughly washed in water. The stained sec- 

 tions are at first of a reddish-purple color, but soon become a deep 

 blue from the slight alkalinity of the tap water used for washing. If 

 necessary this alkalinity may be increased by the addition of one or two 

 drops of ammonia to 500 c.c. of the water used for washing. 



Hematoxylin solutions require air and sunlight for ripening. After 

 ripening is complete the solution should be kept tightly stoppered. The 

 solutions should be filtered before using. Ehrlich's hematoxylin is prob- 

 ably the best nuclear dye for general routine work. Better differentia- 

 tion is usually obtained if the sections are over-stained (5 to 10 minutes) 

 and then, after thorough washing, partially decolorized in a 1 per cent, 

 solution of hydrochloric acid in 70 per cent, alcohol (a few seconds 

 is usually sufficient), washed, and the color restored in an ammoniacal 

 solution (1 per cent, aqueous solution of ammonium hydroxid). The 

 sections must again be thoroughly washed, and the best differentiation 

 is secured if the sections are now placed in very dilute watery eosin for 

 ten to twelve hours. 



Methylene Blue. This dye is a derivative of thionin, and may be 

 similarly used. For staining fresh tissues the dye is used in 2 per cent, 

 aqueous solution. Its preparations are not very permanent. The chief 

 uses of this dye are in combination with eosin as a stain for blood; as 

 a stain for nerve cells according to the method of Nissl; and as applied 

 to living organs as a specific stain for nerve tissues after the method of 

 Ehrlieh. These methods will be described below. 



Methyl Green. This dye is preferable to methylene blue as a stain 

 for fresh tissues. It is used in 2 per cent, aqueous solution and applied 

 as a progressive stain. It also enters into the composition of Ehrlich's 

 triacid mixture. It is strongly basic. 



Carmin. This valuable dye is derived from the cochineal bug, and 

 is used either as a progressive or a regressive stain. For the former, 

 picro-carmin or alum carmin are recommended; for the latter, borax 

 carmin is preferable. 



Borax Carmin : 



Borax 4 grm. 



Distilled water (boiling) 100 c.c.; cool, filter, and add 



Carmin 3 grm. ; when dissolved, add 



70 per cent, alcohol 100 c.c. 



