CHAPTER XIII. 



H.EMATEIN (H^MATOXYLIN) STAINS. 



237. Introduction. Hssmatoxylin is a dye extracted from 

 logwood. It is a substance that oxidises very readily, thus 

 becoming converted into Kasmatein, or, as often happens, into 

 other more highly oxidised products. It appears to be now 

 thoroughly well established (see NIEIZKI, Chemie der organ- 

 ischen Farbstoffe, Berlin, Springer, 1889, pp. 215 21 7, and 

 MAYER, Mitth. Zool. IS tat. Neapel, x, 1891, p. 170) that the 

 colouring agent in solutions of logwood or hsematoxylin is not 

 the hsematoxylin itself, but haematein formed in them (or, in 

 some cases, one of the higher oxidation products). 



Hasmatein is an acid body, a " colour acid ; ' ( 203, 205). 

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

 combined with appropriate mordants it becomes basophilous, 

 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, chrome, iron, 

 copper, and (rarely) vanadium and molybdenum. Aluminium 

 and iron are the mordants most employed, the former fur- 

 nishing lakes used for progressive 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 hssmatein in stain- 

 ing solutions was formerly brought about by allowing solu- 

 tions of hsematoxylin to oxidate spontaneously by exposure 

 to air. The change thus brought about in the solutions is 

 known as " ripening/' and until it has taken place the solu- 

 tions 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 



