STAINING, PRACTICAL AND THEORETICAL 



iv. Leave the preparation to stand until the red colour has 

 disappeared and no further precipitate is formed. This 

 usually takes about four days, during which time the 

 preparation should be checked at intervals by shaking the 

 liquid then placing a drop on filter paper. The red colour 

 of the fuchsin gradually decreases in intensity, while the 

 precipitate in the middle of the filter paper spots will be 

 observed in increasing density. 



V. Collect the precipitate by filtration, and discard the liquid, 

 which is often violet in colour. 



vi. Wash the precipitate, on the filter, with distilled water; 

 then drain and dry. 



vii. Make a saturated solution of the precipitate in 75% 

 alcohol. This stock solution can be kept in the light and 

 at room temperature and it will remain stable for at least 

 a year. 



E. Gomori's paraldehyde fuchsin (staining solution) 



Solution D . . . . . . 5 ml. 



Alcohol, 70% . . . . . . 25 ml. 



Acetic acid, 50% aqueous . . 0-4 ml. 



F. Picro indigocarmine 



Technique: 



1. Dewax the sections and take them down to water through 

 the usual graded alcohols. 



2. Oxidize in Gomori's fluid (solution A) for 20 to 30 seconds. 



3. Rinse quickly in tap water. 



4. Bleach in solution B (sodium metabisulphite). 



5. Wash in running tap water for 30 seconds, 



6. Stain the nuclei with haemalum for one minute. 



7. Wash in running tap water for one minute. 



8. Stain in paraldehyde fuchsin (solution E) for two minutes. 



9. Rinse quickly in tap water. 



10. Stain in picro indigocarmine for 20 seconds. 



1 1 . Rinse in tap water. 



12. Dehydrate through the usual graded alcohols. 



13. Clear in xylol. 



14. Mount in D.P.X., Clearmount, Cristalite, or other syn- 

 thetic neutral resinous media. 



Results: 



Elastic fibres, mast cells, matrix of cartilage: intense purplish 

 red. Acidophilic cytoplasm and muscle fibres: green. Basophilic 

 cytoplasm: grey. Chromatin: black or brown. Collagenous 

 fibres: blue. 



344 



