HARDENING AND FIXING REAGENTS. 



by suspending the tissue in a bottle containing some solution 

 or crystals of Osmic Acid. 



Tissues containing Fat are blackened by Osmic Acid, tee 

 Specific Stains. 



(viii.a) FLEMMING'S FIXING SOLUTION. 



Osmic acid (1 p. c. solution), 80 cc. ; Chromic Acid (10 p. c. 

 solution), 15 cc. ; Glacial Acetic Acid, 10 cc. ; Distilled Water, 

 05 cc. 



This and the following solution are used solely as fixing 

 agents. Tissues are placed in either for about twelve hours ; 

 they are then thoroughly washed in Water and hardened in 

 Alcohol of gradually increasing strength (see Alcohol]. 



Especially useful for fixing tissues undergoing cell division 

 (mitosis). This fluid need not be used in the dark. 



Sections should be stained with Safranine, Hsematoxylin, or 

 Gentian Violet. 



(viiU) POL'S SOLUTION. 



Osmic Acid (1 p. c. solution), 4 cc. ; Chromic Acid (10 p. c. 

 solution), 5 cc. ; Glacial Acetic Acid, 10 cc. ; Distilled Water, 

 181 cc. 



Used for the same purpose as the preceding. 



Flemming's and Fol's solutions represent the maximum and 

 minimum strength of Chrom-Osmic mixtures for fixing pur- 

 poses ; various intermediate strengths are also employed. 



(ix.) PICRIC ACID. 



A saturated aqueous solution ( 1 in 75), or 1 p. c. solution in 70 

 p. c. Alcohol, are used for fixing and hardening. The action 

 is rapid, taking from 1 to 24 hours. 



After hardening, the tissue is washed in 70 p. c. Alcohol 



