660 TECHNIQUE 



3. Dehydrate in 95 per cent, alcohol, clear, and mount. 



Slight differentiation may be obtained by prolonging the wash- 

 ing in water, otherwise the stain is progressive. Much greater 

 differentiation is possible with either eosin method by making the 

 stain very dilute and staining for twenty-four to forty-eight hours. 



Congo Red: 



Congo red 1 grm. 



Distilled water 100 cc. 



A few drops of dilute acetic acid should usually be added to the 

 above ; the bright red color is then exchanged for a dull bluish 

 red, and in this neutralized condition the stain usually gives the 

 highest differentiation. The dye should be used in the same manner 

 as watery eosin (see Method II, above). Congo red gives especially 

 good results when applied to fetal and young tissues. 



Orange G. There are many varieties of orange. The orange G 

 and the aurantia of Griibler will be found satisfactory. As a cyto- 

 plasmic stain the former is preferable. It should be used in the 

 same manner as alcoholic eosin (see Method I, above). 



Fuchsin. Two distinct dyes, the one of acid, the other of basic, 

 properties, pass under this name. Acid fuchsin is a cytoplasmic 

 dye, but when used in acid solution has a slight selective affinity 

 for the nuclei. Basic fuchsin is chiefly useful in bacteriology. It 

 is also used in preparing Weigert's elastic tissue stain. 



DOUBLE STAINING 



Hematein and Eosin: 



1. Stain with one of the hem- 

 atein solutions, preferably Mann's 

 for general use, five minutes. 



2. Wash well in water. 



3. Stain in watery eosin, one 



to ten minutes. Or 3. Dehydrate in 95 per cent. 



alcohol. 



4. Wash quickly in water. 4. Stain in alcoholic eosin, 



one to five minutes. 



5. Dehydrate in absolute al- 5. Dehydrate quickly (one to 

 cohol. five minutes) in absolute alcohol. 



6. Clear and mount. 6. Clear and mount. 



Methyl Blue and Safranin. Methyl blue is a very different 

 dye from methylen blue but is practically identical with water blue 

 (Wasser blau). It is an acid or cytoplasmic stain. 



