Appendix B: Some Standard Reagents and Their Uses 189 



stance of epithelial cells and of connective tissue. As a stain, 

 a saturated aqueous solution of picric acid (stain for 24 to 36 

 hours) followed, after thorough washing in water, by a dilute 

 alcoholic solution of acid fuchsin gives excellent results. 



V. DECALCIFYING FLUIDS 



84. Chromic Acid. Chromic acid diluted to 1 per cent, or in 

 combination with other fluids is frequently used for decalcifica- 

 tion. Chromic acid, 1 gram ; water, 200 c.c. ; nitric acid, 2 c.c., is a 

 mixture widely used. It decalcifies well but acts more slowly 

 than the 10 per cent, nitric acid mixture. Bone should first be 

 hardened in Muller's fluid (8). 



85. Nitric Acid. A 10 per cent, solution of nitric acid in 70 

 per cent, alcohol may be used. If nitric acid is used for young 

 or foetal bones, it is advisable to use only 1 part of the acid to 99 

 parts of the alcohol. After washing out in 70 per cent, alcohol, 

 the decalcified bone may be kept in 95 per cent, alcohol. 



86. Phloroglucin Method. This is a rapid method. Young 

 bones may be decalcified in half an hour and old and hard ones 

 in a few hours. Teeth require a somewhat longer time. Phloro- 

 glucin itself does not decalcify, but protects the tissue from the 

 action of the strong nitric acid. One gram of phloroglucin is 

 dissolved in 10 c.c. of pure non-fuming nitric acid with the aid 

 of gentle heat. Ten c.c. of nitric acid in 100 c.c. of water is added 

 to the mixture. 



87. Picric Acid. A solution kept fully saturated is useful for 

 delicate bones. It stains and decalcifies the tissue at the same 

 time. Wash in 70 per cent, alcohol. 



88. Von Ebner's Fluid.- 



Alcohol, 95 per cent 500.0 c.c. 



Water 100.0 c.c. 



Sodium chloride 2.5 grams 



Hydrochloric acid 5.5 c.c. 



This is an excellent fluid for bone because in it the ground 

 substance of the bone does not swell up. Sections are best 

 examined in a 10 per cent, solution of sodium chloride. 



