36 PRACTICAL HISTOLOGY. 



Garbini divides hardening reagents into the two following classes, 

 according as the tissues after hardening stain readily or do not 

 stain readily with carmine : 



Tissues stain readily after 

 hardening in 



Vapour of osmic acid. 



Corrosive sublimate. 



Picric acid and solutions contain- 



. in .& it; -. 

 Nitric acid. 



Silver nitrate (weak solution). 

 Alcohol. 



( Chromic acid and its compounds. 



Tissues stain with dim- | Osmic acid in solution. 



culty after hardening \ Silver nitrate (strong solution). 



in | Chloride of gold. 



L Perch loride of iron. 



Alcohol, picric acid and its compounds, and nitric acid, coagulate 

 the albumen of the tissues. Chromic acid, or solutions containing 

 it, or its salts form chemical compounds with substances in the 

 tissues. Osmic acid, mercuric chloride, and gold are decomposed 

 when they come in contact with the tissues, and are deposited in 

 the tissues as an inorganic precipitate. 



VII. DECALCIFYING FLUIDS. 



General Directions. Use small parts of the tissue or organ, and 

 a large quantity of the decalcifying solution. Renew the latter 

 often. In all cases harden the tissue thoroughly, e.(/., in alcohol 

 or Miiller's fluid, before it is decalcified. After decalcification every 

 trace of the decalcifying fluid must be thoroughly removed by pro- 

 longed washing (for a day or two) in water or other fluid. The 

 tissue is then finally hardened in alcohol. 



1. Chromic Acid. .1 to .5 per cent. 



2. Chromic and Nitric Acid Fluid. 



Chromic acid ..... i gram. 

 Water ...... 200 cc. 



Nitric acid . . . . . 2 ,, 



3. Chromic Acid and Hydrochloric Acid Fluid (Bayerl's Fluid}. 



Chromic acid ..... I part. 

 HC1 . . . . i 



Water . . . . 100 parts. 



This is specially good for young bones and for ossifying bone, 

 but it is solely for decalcifying. 



4. Saturated Solution of Picric Acid. The solution must be 



