STAINING, PRACTICAL AND THEORETICAL 

 Br Br 



+ 2 



1— COONa 



-N(CH3)2 



+ 



ci- 



Eosin 

 (i niol) 



Methylene blue 

 (2 mols) 



N(CH3)2 



N(CH3)2 



+ 



N(CH3)2 



N(CH3)2 



+ 2NaCl 



Eosin-methylene blue {Jenner) 

 (i mol) 



with the organic portion of the other dye, which is negatively 

 charged : 



The precipitated Jenner stain is insoluble in water. It is dried 

 and dissolved in alcohoL Out of contact with tissues or other 

 stainable material the dye-ions remain united as one molecule, 

 but as soon as the solution is applied to tissues dissociation takes 

 place, but not completely, and we have a proportion of un- 

 dissociated compound-dye molecules which impart shades of 

 purple and violet to certain tissue elements. We also have a 

 proportion of the component dye-ions which stain different 

 elements present in the tissues. Accordingly, the positively 

 charged methylene blue ion is attracted to the acidic tissue 

 elements. The negatively charged eosin ions are attracted to the 

 basic tissue elements. It would appear that this is a case of 

 competition between an acid dye-ion and acidic tissue elements 



32 



