UNNA'S H JIM ATE IN STAIN. 115 



which may be at any moment converted into a totally ripe 

 one by the process given in the last . 



This result maybe attained by simply adding a reducing 

 agent to the solution. Various reducing agents are available 

 for this purpose (see the original paper) ; the most convenient 

 method is the simple addition of a little sulphur. The fol- 

 lowing formula is recommended : 



Haematoxylin ..... 1 



Alum 10 



Alcohol 100 



Water 200 



Sublimed sulphur .... 2 



If the sulphur be added to the haematoxylin solution only 

 when the latter has become somewhat strongly blue, i. e. 

 after two or three days' time, the stage of oxidation attained 

 by the solution will be fixed by the sulphur. The solution 

 in this state may be used for staining. It will not give so 

 energetic a stain as the solutions totally ripened with peroxide 

 of hydrogen, and the stain will be somewhat more diffuse, but 

 washing out with acids will not be necessary. If an energetic 

 and more purely nuclear stain be desired, the solution should 

 be treated with neutralised peroxide of hydrogen, as described 

 in the last ; sections should be stained in it at once, and 

 quickly brought into glacial acetic acid (where they should 

 only remain for a moment), or into HC1 alcohol, for washing 

 out. 



177. General Remarks. We have the coal-tar colours for 

 staining sections, and we have carmine and cochineal for 

 staining in the mass. What, then, do we want haematoxylin 

 for? The answer is that we sometimes want it for staining 

 in the mass on account of the faculty it has of readily staining 

 tissues that have been treated with chromic and osmic mix- 

 tures. This it does in general better than any carmine or 

 cochineal. We want it also for some special purposes, such 

 as staining the Nebenkern and achromatic figure of nuclei, 

 and for nerve researches and other special histological 

 objects. 



None of the old solutions of haamatoxylin are perfectly 

 stable ; only one or two are fairly so. 



