SECTION ONE 



and pyronin Y or G (molecular weight 303), are in competition 

 with each other, their differential staining of the two types of 

 nucleic acids (see Kurnick's method, page 297) might conceivably 

 be influenced by the differences between the molecular weight of 

 these two dyes. Pyronin can be replaced by toluidine blue 

 Korson (1951) for staining RNA. Toluidine blue is a basic dye 

 whose molecular weight (306) is very close to that of pyronin Y. 

 It might prove worth while to try other basic dyes of around the 

 same molecular weight as pyronin Y, in place of the latter for 

 RNA. 



Acid fuchsin, as stated elsewhere in this book, is an amphoteric 

 dye. In practice, however, it behaves as an acid dye when applied 

 to tissues. It unites with tissue elements that are basic in reaction. 

 It does, however, behave as a base towards other acid dyes. It 

 also behaves as an acid towards basic dyes. 



Basic dyes are usually employed for staining mitochondria. 

 Examples of such dyes are janus green, amethyst violet, janus 

 black, janus blue, methylene blue, pinacynaol, toluidine blue. 



There appears to be a possibility, therefore, that when acid 

 fuchsin stains mitochondria it is acting as a basic dye through 

 its amino (basic) groups uniting with acidic groups (probably 

 phosphate) of mitochondria. On the other hand, perhaps the 

 acid fuchsin is acting as an acid dye and is not reacting with the 

 same chemical groups, of mitochondria, as are the basic dyes 

 mentioned above. Osmic acid, of course, stains mitochondria; in 

 this case presumably through the lipid moiety of the latter, so 

 that the staining reaction would not be the same. 



In general, sulphonated (acid) dyes appear to hold on to tissues 

 stained by them and are not completely removed by ordinary 

 solvents. Mention is made elsewhere in this book of competition 

 between pairs and trios of sulphonated acid dyes for certain 

 tissue elements. One of the dyes in such staining procedures will 

 replace the other in certain tissue elements. With few exceptions 

 it is the sulphonated dye with the lower molecular weight that 

 replaces the one with the higher molecular weight. Acid fuchsin 

 (molecular weight 586), for instance, captures certain tissue ele- 

 ments previously stained by light green (molecular weight 793). 

 Orange G (molecular weight 452) will replace acid fuchsin as well 

 as light green. Many more examples could be quoted but space 

 does not permit. But removal of one sulphonated dye by another 



