306 HISTOLOGICAL TECHNIQUE. 



The above method for staining with hematoxylin and eosin is 

 highly recommended for general routine work. 

 2. Neutral Carmine. — 



The solution is allowed to remain exposed to the air until the 

 odor of ammonia is no longer perceptible. It is then filtered into 

 a bottle, where it is kept till needed. 



Neutral carmine gives a diffuse stain, resembling that of eosin, 

 but rather clearer in character. It is employed in a greatly diluted 

 form, according to the following directions : 



One drop of the neutral carmine is mixed with about 20 cc. of 

 distilled water. A trace of acetic acid is then added by dipping a 

 platinum needle into the acid and stirring the diluted dye with the 

 acidulated needle. A piece of filter-paper is then placed upon the 

 bottom of the dish, and the sections to be stained are transferred 

 from distilled water to the dye and distributed upon the paper in 

 such a way that they do not lie over each other. The dye acts 

 very slowly, twenty-four hours being none too long for good results. 

 If the staining be hastened by using a stronger solution, it suffers 

 in sharpness. After staining, the sections are thoroughly washed 

 in distilled water, and may then be subjected to a nuclear dye, such 

 as hematoxylin. The proper aeidulation of the diluted dye is of 

 importance for the success of this method. If the solution is not 

 sufficiently neutralized, the sections will not be stained ; if it is too 

 acid, precipitation of the carmine will take place. 



3. Alum-carmine. — 



The alum is dissolved in the water with the aid of heat, the 

 carmine then added, and the mixture kept at the boiling-point for 

 about half an hour. It is then allowed to cool and filtered into the 

 stock-bottle. Two or three drops of deliquesced carbolic acid may 

 be added to prevent the development of fungi. 



Sections are stained in the undiluted, but filtered, dye for at least 



