SECTION THREE 



Acetic Acid, Glacial 



Recommended for : 

 . Rapid fixation of strongly contracting organisms. 



Technique: 



Fix in the warm acid for a maximum period of fifteen minutes; 

 then remove excess acid by washing in 30-50% alcohol. 



Remarks: 



Acetic acid glacial is rarely used alone : it causes the swelling oi 

 cell constituents, etc., and it is of most value when mixed with such 

 substances as formalin, alcohol, mercuric chloride, etc., to counter- 

 act their shrinking effect. 



Acetone 



Recommended for : 



Rapid fixation of brain tissue for rabies diagnosis (R. D. Lillie, 

 1948). It is also employed for fixing tissue enzymes, particularly 

 phosphatases and lipases. 



Technique: 



Thin slices of tissue are fixed in pure acetone for twelve to 

 twenty-four hours at 0° C. ; they are then dehydrated by immer- 

 sion in two changes of pure acetone for two hours in each at room 

 temperature, and afterwards cleared by immersing for half an hour 

 in each of two changes of benzene before infiltration with paraffin 

 wax. 



Alcohol, Absolute 



Recommended for: 



Glycogen, Amyloid, Fibrin, Hyaline, Haemofuscin, Phos- 

 phatase. 



Technique: 



Fix from two hours to several days according to the nature of 

 the material; dehydrate; clear. 



473 



