24 



Accessory Metal Staining Solutions 



Decimal Divisions Used in Chapter 



AMS 10 SOLUTIONS USED BEFORE STAINING ("ACCELERATORS" AND 

 "MORDANTS") 

 100 General observations 



11 Formaldehyde mixtures 

 11.1 Formulas 



12 Alcohol mixtures 

 12.1 Formulas 



13 Other mixtures 

 13.1 Formulas 



AMS 20 SOLUTIONS USED AFTER STAINING 

 200 General observations 



21 Developers 

 21.1 Formulas 



22 Toning solutions 

 22.1 Formulas 



23 Differentiating solutions 

 23.1 Formulas 



24 Fixing solutions 

 24.1 Formulas 



AMS 10 Solutions Used Before Staining 



AMS 10.0 GENERAL OBSERVATIONS 



As Chapter 18 has been devoted to fixative formulas, it appears necessary to justify 

 the retention in this place of formulas used to fix materials before metal staining tech- 

 niques. Formulas are retained in this section only when they are not considered by the 

 author to be adapted to any other purpose. Fixatives developed for use prior to silver 

 staining which would appear to have applications outside this specific field are given in 

 Chapter 18. It is impossible, moreover, to distinguish in many of the formulas given in 

 this chapter among those intended to fix the tissues, those designed to serve as mor- 

 dants, and those supjiosed to exercise some physical effect so as to render more apparent 

 some structure in the material after it has been metal-stained. Solutions of uranium, 

 cobalt, and the like, might be considered chemical mordants which would render ma- 

 terials subsequently stained more clearly apparent: the reverse is the case. These ma- 

 terials are used mostly as inhibitors which, by preventing the absorption of various 

 metal-stains upon the nervous elements of nervous structures, permit the demonstration 

 of their supi)orting or connective tissues. The exact role jilayed by pyridine, so fre- 

 quently an ingredient of this group of solutions, is again doubtful; it has been suggested 

 that it may cause no more tlian the differential shrinking of certain structures, particu- 

 larly neurofibrillae, with the result that they become mechanically differentiated. It is 

 recognized that the division into aqueous and alcoholic solutions is untenable on 

 scientific grounds, but it is retained on grounds of convenience. 



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