FIXING AND HARDENING REAGENTS. 



35 



day, and once or twice afterwards, and on each occasion alter the 

 position of the tissues. If the fluid becomes turbid, change it at 

 once (p. 30). 



Label each bottle carefully, and place it in a cool place. Keep 

 all chromic acid and solutions containing it or its salts in the 

 dark. 



Tissues hardened in alcohol and picric acid must not be placed 

 in water, but directly into the various strengths of alcohol, 

 beginning with 50 per cent, and rising to 95 per cent. Wash 

 out by means of alcohol as much of the picric acid as 

 possible. 



For other tissues, hardened in chromium salts (p. 30), the excess 

 of these salts may be removed from them by washing in water (for 

 certain special purposes this is omitted), and they are then transferred 

 first to weak spirit, in which they may remain a few days, and then 

 to the stronger alcohols (p. 28). To avoid the deposits which occur 

 in chromic acid preparations when they are placed in alcohol, keep 

 them in the dark. If kept in the dark, as Hans Virchow has 

 shown, there is no deposit formed when a tissue hardened in 

 chromic acid or Miiller's fluid is placed in spirit. Kept in this 

 way, I find that the alcohol remains quite clear and no deposit 

 forms. 



Scheme for the, Hardening of Tissues (Garbini). 

 Fresh Object. 



Picric acid or Chromic acid or 



Sublimate. 



solution con- 

 taining it. 



Alcohol 



its com 



>ounds. 



Osmic acid. 



Running water. 



Running water. Distilled water. 



Alcohol (50 p.c.) Alcohol (50 p. c.) Cyanide of Potassiu in. 

 in dark. (iodated). 



Alcohol (70 p.c.) Alcohol (70 p.c.) Alcohol (50 p.c.). 

 in dark. (iodated). 



I I 



Alcohol (70 p. c. ). 



