STAINS AND STAINING 19 



alum, and then the potassium iodate added; this oxidizes it instantly, taking 

 the place of the long ripening process of other hematoxylin solutions. The 

 glycerin is added last. The -stain may be used either for sections or whole- 

 mounts, and the method differs slightly in each case. 



METHOD FOR SECTIONS: 



1. Accumulate the sections in water. 



2. Transfer them to undiluted stain until the nuclei (or, in plant tissues, 

 xylem) is sufficiently stained. This takes 5 to 10 minutes for a plant sec- 

 tion but may take several hours for animal tissues. 



3. Then wash each slide in distilled water until no more color comes away. 



4. Differentiate the sections in the differentiating solution until the nuclei 

 are darkly stained, while the plasma is only lightly stained. In plant tis- 

 sues it is possible to remove the stain from everything except the xylem. 



5. Transfer the sections to alkaline tap water until bright blue. 



METHOD FOR WHOLE OBJECTS: 



1. Accumulate the objects in water. 



2. Transfer the objects to one part of stain plus 10 parts of distilled water 

 for 3 to 10 minutes. 



3. Wash them in distilled water until no more color comes away. 



4. Differentiate each object in the differentiating solution until the whole 

 object appears a fairly pale pink. Remember, in judging the amount of 

 differentiation required, that the object will appear very much more darkly 

 stained after it has been blued. 



5. Transfer the objects to tap water until blue throughout. 



Indirect Carmine Nuclear Stains 



Both of the carmine formulae given below can be used as direct stains if they 

 are diluted several hundred times with an alum solution. It is not safe to dilute 

 them with distilled water, for there is a risk of the carmine precipitating out, 

 particularly within the cavities of whole animals from which it is almost 

 impossible to remove it subsequently. The best known of all the carmine 

 nuclear stains is: 



Grenacher's Alcoholic Borax Carmine: 

 Staining solution 



Boil together 10 Gm. of borax and 8 Gm. of carmine in 250 ml. of water 

 for about 30 minutes. Cool overnight and filter. Evaporate the filtrate to 

 dryness and then store this powder, labeled as "Borax Carmine Powder." 

 This powder may be dissolved in any strength alcohol from 30 per cent 

 to 70 per cent; in all cases a saturated solution should be employed. 

 This is the original method of making up the solution and is undoubt- 

 edly the best. 



