122 CYTOLOGICAL TECHNIQUE 



behaves towards mordants very much like the latter dye. Its 

 colour (crimson) does not undergo much change when it links 

 itself to aluminium, the mordant most commonly used. 



One of the best solutions is Mayer's carmalum,^^^ which con- 

 tains carminic acid, potassium alum, and water, with thymol, 

 salicylic acid, or sodium salicylate as disinfectant. It is suitable 

 for use with both sections and whole mounts. It may be used 

 either progressively or regressively. Potassium alum (5 % aqueous) 

 readily extracts any excess of colour. This is a very easy dye to use, 

 since it lends itself to leisurely progressive colouring. The colour 

 is well maintained in both hydrophil and hydrophobe mounting 

 media. 



