8 NORMAL HISTOLOGY. 



Carmine. This is a red stain, and is employed in 

 the same manner as haematoxylin, and is useful 

 where we do not wish as great body of color in the 

 specimen as the haematoxylin imparts. It may be 

 prepared by dissolving two grms. of commercial 

 carmine in a few drops of strong ammonia, and 

 adding 100 c. c. of water. It should be allowed to 

 stand in an open vessel until the excess of ammonia 

 evaporates. As a rule, old carmine solutions stain 

 better than those recently prepared. To prevent the 

 formation of moulds, a few bits of gum camphor are 

 placed in the bottle. 



Pier o-Car mine. With this staining fluid we obtain 

 a double stain. Some of the elements are stained 

 yellow by the picric acid, others nuclei are stained 

 red by the carmine. The following formula of 

 Weigert gives excellent results : Soak i grm. of car- 

 mine in 4 c. c. of strong ammonia for twenty-four 

 hours in a closed vessel ; then add 100 c. c. of a 

 saturated solution of picric acid in water, and allow 

 to stand for twenty-four hours. Filter, and add hy- 

 dric acetate to the filtrate, drop by drop, until a 

 slight precipitate remains even after stirring. Allow 

 this fluid to stand for twenty-four hours, when a 

 precipitate will form which cannot be wholly re- 

 moved by filtering; add ammonia, drop by drop, at 

 intervals of twenty-four hours, until a clear fluid is 

 obtained. If the fluid stains too yellow, add a few 

 drops of hydric acetate ; if too red, a few drops of 

 ammonia. 



