MEDICAL AND BIOLOGICAL STAINING TECHNIQUES 



Allen's Fixative (B.15) 



Recommended for : 



Chromosomes; plant tissues, particularly buds. 



Technique: 



Fix tissues from four to sixteen hours then immerse in frequent 

 changes of 70% alcohol over a period of forty-eight hours or until 

 the yellow coloration due to picric acid ceases to come out. 



Remarks: 



The solution deteriorates very rapidly and it is, therefore, essen- 

 tial that this fixative should be prepared only when it is required 

 for immediate use. 



Bouin's Fluid 



Recommended for : 



Embryological specimens, for elementary bodies, Purkinje cells, 

 Argentaffin reaction, and for animal tissues in general. 



Formula: 



Picric acid, saturated aqueous . . 75 ml. 



Formalin . . . . . . . . 25 ml. 



Glacial acetic acid . . . . • • 5 ml. 



Technique: 



Fix from eighteen hours to two days; then wash in 50% fol- 

 lowed by 70% alcohol until most of the yellow coloration, due to 

 picric acid, is extracted. Alternatively the picric acid can be 

 washed out with the alcohols after the tissues have been embedded 

 and sectioned. 



It is not essential that all the picric acid, which serves as a 



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