SECTION TWO 



(a) The acidified fuchsin solution is unreliable after it has been 

 kept in stock for a week or so. The reason for this is explained 

 on page 85. However, unacidified concentrated solutions (5 or 

 10%) of the dye remain stable indefinitely. It is recommended, 

 therefore, that a 10% solution of acid fuchsin in distilled water be 

 kept as the stock solution, and dilutions made from this in quanti- 

 ties sufficient for one week's use, as follows: 



Acid fuchsin, 10% aqueous . . 5 ml. 

 Distilled water . . . . . . 91 ml. 



Glacial acetic acid . . . . 4 ml. 



Notes: 



(b) It was found by the authors that the Falg method applied 

 to neurological tissues gave results that were pedagogically 

 equivalent to the Weigert-Pal method, but were obtained in a 

 matter of only a few minutes as compared with a few weeks 

 required for the performance of the latter method. 



(c) It should be noted that tissues to be stained by any of the 

 compound fuchsinic acid techniques (Falg, Trifalgic acid, Falgog, 

 Falgose and basic and standard Faviols, etc.) should be fixed in 

 10% formaldehyde which has not been neutralized with metallic 

 compounds. However, Professor MacConaill has since found 

 that instead of pure formalin solution, acetic acid-formalin or 

 Susa may be used for fixation. If Susa is used care must be taken 

 to remove all the mercuric chloride from the sections before 

 staining. 



(d) If after staining with the acid fuchsin the preparations are 

 immersed in a bath of 2% aqueous acetic acid for five minutes 

 before staining with light green, the subsequent picture is in 

 green and red only, and not in the typical Falg colours. The 

 authors found that this is due to blockage of the amino groups of 

 acid fuchsin through union with the acetate radicals thereby 

 preventing the formation of the falgic acids to which the poly- 

 chrome effects of Falg staining are due. Compounds formed 

 by the union of acid fuchsin and acetic acid have since been 

 isolated in the dry form (see page 85). The highest homologue, 

 nono-fuchsinic acid, will not unite with light green at all. 



(e) The Falg method was developed during the course of an 

 investigation which was originally intended as a continuation of 



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