LIPIDS AND CHOLESTEROL 41 



containing 1% acetic acid until a deep brick-red color and a 

 consistency of milk is obtained. Stir well during the addition. 

 Hold the mixture at 37° for 2 hr. to evaporate the acetone or let 

 stand in a warm room overnight. Filter off sediment through coarse 

 paper. 

 1 % Gelatin Solution. 



PROCEDURE 



1. Transfer frozen sections from water to 1% gelatin soln. for 

 2-3 min. 



2. Stain for 30 min. at 37° with the suspension. 



3. Wash sections in 1 % gelatin soln. for 2-3 min. 



4. Wash well in water. 



5. Counterstain, if desired, and mount in glycerin jelly or Karo 

 syrup. 



Schultz Cholesterol Test 



SPECIAL REAGENTS 



2.5% Iron Alum (NH4)2S04.Fe2(S04).-5.24H20. 



Concentrated Sulj uric-Glacial Acetic Acid Mixture. Add the sul- 

 furic acid slowly to an equal volume of glacial acetic acid, stirring 

 and cooling the while. (Only the purest acids are suitable and 

 the sulfuric must contain at least 98% sulfuric acid. The reagent 

 is hydroscopic and must be protected from atmospheric moisture.) 



PROCEDURE 



1. Place formalin-fixed frozen sections in the iron alum solution 

 for 3 days at 37°. 



2. Rinse in distilled water, mount on slides and blot with filter 

 paper. 



3. Add a few drops of the acid mixture and cover with a cover- 

 glass. 



Result. A positive test for cholesterol, or its esters, is indicated 

 by the appearance of a blue-green color which reaches its maximum 

 intensity within a few min. Within 30 min. the sections acquire a 

 brown discoloration. The appearance of large numbers of bubbles 

 results from impure acids. 



