CHAPTER XV 

 H^MATEIN (HEMATOXYLIN) STAINS 



277. Introduction. Hcematoxylin is a dye extracted from log- 

 wood. It is a substance that oxidises very readily, thus becoming 

 converted into hcvmatein, or, as often happens, into other more 

 highly oxidised products. It appears to be now thoroughly well 

 established (see Nietzki, Chemie der organischen Fdrbstoffe, 

 Berlin, Springer, 1889, pp. 215—217, and Mayer, Mitth. Zool. 

 Stat. Neapel, x, 1891, p. 170) that the colouring agent in solutions 

 of logwood or lijematoxylin is not the haematoxylin itself, but 

 hsematein formed in them (or, in some cases, one of the higher 

 oxidation products). 



Ha^matein is an acid body, a " colour acid " (§§ 233, 237). 

 Substantively employed, it is a very weak plasma stain. But 

 combined with appropriate mordants it becomes basic, and can 

 be made to give a powerful nuclear stain, or at the same time a 

 nuclear and a selective plasma stain. The mordants employed in 

 histology are aluminium, chromium, iron, copper, and (rarely) 

 vanadium and molybdenum. Aluminium and iron salts are the 

 mordants most employed, the former furnishing lakes used for pro- 

 gressive staining of material in bulk, the latter forming in most 

 cases in the tissues a lake that requires differentiation, and is 

 only applicable to the staining of sections. 



The presence of a sufficient amount of hsematein in staining 

 solutions was formerly brought about by allowing solutions of 

 haematoxylin to oxidate spontaneously by exposure to air. The 

 change thus brought about in the solutions is known as " ripen- 

 ing," and until it has taken place the solutions are not fit to use 

 for staining. 



It was discovered by Mayer and Unna independently (see 

 Mayer in Mitth. Zool. Stat. Neapel, x, 1891, pp. 170—186 ; Unna 

 in Zeit. wiss. Mik., viii, 1892, p. 483) that nothing is easier than 

 to bring about this change artificially ; all that is necessary being, 

 for instance, to add to a solution of haematoxylin containing alum 

 a little neutralised solution of peroxide of hydrogen or other 

 powerful oxidising agent.* The solution becomes almost instan- 

 taneously dark blue, " ripe " and fit for staining. Other methods 



* Reintroduced (Zeit. iviss. Mik., xxix, 1912, p. 69) by Piazza, 

 who adds to Boehmer's solution about 20 per cent., to Delafield's about 

 7 per cent., to Ehrlich's about 12 per cent, of peroxide of hydrogen. 



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