184 Animal Micrology 



used in saturated aqueous solution. The solution does not keep 

 very well. 



60. Orcein (Unna's method for elastic fibers). 



Orcein (Griibler's) 1 gram 



Hydrochloric acid 1 c.c. 



Absolute alcohol 100 c.c. 



Sections are stained in a watch-glass or porcelain dish. The 

 dish is warmed over a flame or in an oven until the stain 

 becomes thick through the evaporation of the alcohol. Rinse the 

 stained sections thoroughly in alcohol, clear in xylol and mount 

 in balsam. Elastic fibers should appear dark brown. 



61. Paracarmine (Mayer's). 



Carminic acid 1 .0 gram 



Aluminium chloride 0.5 gram 



Calcium chloride . 4.0 grams 



Alcohol, 70 per cent 100.0 c.c. 



Paracarmine is an excellent stain for large objects. It does 

 not overstain ordinarily. The stained tissue is washed in 70 per 

 cent, alcohol. In case overstaining occurs add 2.5 per cent gla- 

 cial acetic acid or 0.5 per cent, aluminium chloride to the alcohol 

 used for washing. Objects to be stained should not have an 

 alkaline reaction nor contain limy materials. 



62. Picric Acid. Picric acid is widely used as a contrast stain 

 with carmine, hematoxylin, etc. It is best manipulated as a stain 

 by adding a little to each of the alcohols used in dehydrating, 

 after application of the nuclear stain. However, if acid alcohol 

 is to be used, the picric acid should be used only in the grades 

 above the acid alcohol. It may be employed in staining entire 

 objects as well as sections. See also remarks on washing under 2 1 . 



63. Picro-Carmine. This is a very useful double stain. Tissues 

 stained in it should never be washed in water or a low percentage 

 of alcohol because these extract the yellow color very rapidly. 

 If the tissues are to be mounted in glycerin or glycerin jelly, 

 transfer them to the mounting fluid without washing; if they are 

 to be mounted in balsam, to prevent the extraction of the stain, 

 picric acid should be added to each of the alcohols through which 

 the material will pass. Picro-carmine solutions are likely to dis- 

 solve off sections which have been affixed by means of albumen 



