NUCLEAR STAINS. 23 



undergo a change technically called " ripening," after which 

 the staining is much more precise. 



The ripening process appears to depend upon conversion of 

 part of the Hsematoxylin into Hsematein by absorption of 

 oxygen from the air in presence of traces of free Ammonia. 

 By dissolving Heematoxylin crystals in Proof Spirit with -J- of 

 their weight of Ammonium Carbonate, and exposing to the 

 air in a shallow dish, the " ripening " process will be more 

 complete in 24 hours than after 3 months' exposure in the 

 usual way. 



As solutions, even when made from the same formula, 

 differ widely in their staining power according to the ripen- 

 ing which the Heematoxylin has undergone, no very definite 

 directions as to dilution and time of immersion can be given. 

 As a rough guide, it may be stated that a well-ripened 

 Ehrlich's solution, diluted 1 to 4 of Distilled Water, and 

 Delafield's diluted 1 to 10, will stain well in about 20 

 minutes. 



Accidental overstaining may be remedied by immersing the 

 sections in 70 p. c. Alcohol, to which -jV r ^ P er cent, of 

 strong Hydrochloric Acid has been added. When the over- 

 staining is very deep, J p. c. Acid may be used to save time, 

 but requires caution. The sections are subsequently washed 

 in a dilute aqueous solution of Bicarbonate of Sodium ( 1 grain 

 in 2 ounces). 



(i.) BOHMER'S H-ffiMATOXYLIN. 



(a) Haematoxylin, 1 grm. ; Absolute Alcohol, 10 cc. 



(b) Alum (Ammonia), 10 grms. ; Distilled Water, 200 cc. 

 Mix the two solutions, and after a week filter. 



This is probably the earliest formula, as Hsematoxylin 

 staining was introduced by Bb'hmer. 



