Phenyl Methane Dye^ 151 



greatest impetus. Special significance has attached to the HIO4- 

 Schiff technic, in which the use of the Schiff reagent is preceded by 

 oxidation with periodic acid (HIO4), as first proposed by McManus 

 (1946). It is considered that certain polysaccharides (and their 

 derivatives) which contain 1,2-glycol and a-amino-alcohol groups 

 react with the periodic acid (or other oxidant) to produce aldehyde 

 groups, and that the latter react with the Schiff reagent to bring 

 out the violet color. This has enabled histochemists to deter- 

 mine the locations of the compounds in question within the cell. 

 Histochemists are proving much more exacting in their require- 

 ments for a basic fuchsin than were histologists or chemists using 

 the Schiff reagent. As a result of trying to meet their require- 

 ments, the quality of basic fuchsin on the American market has 

 been improving in recent years. 



Early editions of this book contained statements, realized at the 

 time to be largely provisional, to indicate which types of fuchsin 

 are most satisfactory for the various purposes. Data that have 

 been accumulated since 1929, however, seem to show pretty 

 definitely that the exact chemical nature of basic fuchsin itself is 

 of comparatively little importance. Good results for practically 

 any purpose have been obtained with pararosanilin, rosanilin, 

 new fuchsin, and even with the seldom-encountered magenta II; 

 and the dyes have proved equally satisfactory whether in the 

 form of chlorides or acetates, the two most common salts of this 

 dye. From the standpoint of ordinary staining, in fact, it was 

 realized a long while ago that the samples furnished by the stain 

 companies varied very little in their performance. 



In their behavior in the Endo medium and in the Feulgen 

 technic, however, the samples were found to be quite dissimilar, 

 and it was some time before any clue could be obtained as to the 

 cause of their differences. It has finally been concluded, however, 

 that the variations which occur are due to foreign ingredients 

 which are almost always present in these dyes. 



The problem of the Endo medium was solved first. It was 

 learned (Conn and Darrow, 1934) that almost any sample of 

 basic fuchsin will give good results in the Endo medium if the 

 formula of that medium is carefully adjusted so as to avoid either 

 an excess or a deficiency of sulfite in proportion to the fuchsin. 

 Another complication arises from the fact that the 1936 edition of 

 the Standard Methods of Water Analysis (of the American Public 

 Health Association) lists two different formulae for the Endo 

 medium, of which Formula II calls for K2HPO4, while formula I 

 does not. For some reason, not yet explained, it is possible for a 

 particular sample of basic fuchsin to give good results in Formula 

 II while appearing too deeply colored in Formula I; or to be satis- 

 factory in Formula I but not allowing sufficient color restoration 

 by lactose fermenters if Formula II be used. As a result it is 



