656 TECHNIQUE 



stain, Sudan III for fat, the intra vitam staining of nerve tissues 

 with methylen blue, etc. 



Mordants. The successful application of a dye requires that 

 the tissue shall have an affinity for the stain. This affinity may be 

 either natural or artificial, e. g., eosin will color nearly all tissues 

 under any ordinary conditions without the aid of any other reagent ; 

 hematoxylin, on the other hand, stains ordinary tissues but slightly, 

 but its action is much enhanced by first acting upon the tissue with 

 alum or a similar reagent. The alum, in this case, serves as a 

 mordant. 



A mordant should have a strong affinity for both the stain and 

 the tissue. Hence it is that, after a tissue has been once stained by 

 the aid of a mordant, it may be decolorized, partially or completely, 

 by the second application of the same or another mordant of equal 

 strength. 



SINGLE STAINS WITH NUCLEAK DYES 



Hematein. Hematein is the active principle of the dye, hema- 

 toxylin, obtained by extracting logwood. Hematein is derived 

 from solutions of hematoxylin by oxidation, either by chemical 

 reagents or by prolonged exposure to the air. As a dye it must be 

 combined with a mordant, which, most frequently, is some form of 

 alum. The following formulas are recommended : 

 Alum Hematein (Mayer) : 



Alum hematein (Griibler's) 0.2 grm. 



95 per cent, alcohol 5 cc. 



Saturated aqueous solution of ammonium 



alum 100 cc. 



About 10 grm. of alum are required for this solution. The 

 hematein should be first dissolved in the alcohol, with gentle heat 

 if necessary, and afterward added to the warm solution of alum. 

 The fluid is ready for use in two or three days, but will increase in 

 strength for several week^ ; it then requires dilution. 

 Bohmer's Hematoxylin : 



Hematoxylin 0.5 grm. 



Absolute alcohol 5 cc. 



Saturated aqueous solution of potassium 



alum 100 cc. 



The ingredients should be mixed as above and allowed to stand 

 for eight to ten days in an open bottle. Filter. Kipening will 

 continue for some weeks, and the dye will require dilution from 

 time to time with a saturated solution of potassium alum. 



