746 HISTOLOGIC TECHNIG 



ation 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 c.c. 



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 differen- 

 tiation. 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 Gr 

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

 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. 



It is recommended that euparal be used as a mounting medium 

 with this group of stains. The tissue may be mounted directly from 90 

 per cent, alcohol. 



DOUBLE STAINING 



Hematein and Eosin : 



1. Stain with one of the hem- 

 atein solutions, preferably Mann's 

 or Ehrlich'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. 



