CHAPTER XIII. 



HJilMATEIN (HiEMATOXYLIN) STAINS. 



237. Introduction. — Hsematoxylin is a dye extracted from 

 logwood. It is a substance that oxidises vei-y readily^ thus 

 becoming" converted into hsematein, or, as often happens, into 

 other more highly oxidised products. It appears to be now 

 thoi'oughly well established (see Nietzki, Chemie der organ- 

 ischen Fdrbstoffe, Berlin, Springer, 1889, pp. 215 — 217, and 

 Matbe, Mitth. Zool. Stat. Neapel, x, 1891, p. 170) that the 

 colouring agent in solutions of logwood or hasmatoxyliu is not 

 the hsematoxylin itself, but h^matein formed in them (or, in 

 some cases, one of the higher oxidation products). 



Hffimatein 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 hsematein 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 Mayek and Unna independently (see 

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

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



