SECTION THREE 



2. Transfer to a second bath of waterwax and leave for an hour. 



3. Transfer to a third bath of wax for an hour, or longer. 



4. Cast the block and leave it to cool in the atmosphere or in a 

 refrigerator. Care must be taken not to allow the block to come 

 into contact with water. 



5 . After cutting sections, float them out on water, which dissolves 

 away the wax, and take them up on slides. 



6. Stain, dehydrate and mount immediately in the usual way. 



Notes: 



{a) Fat, if present, should be dissolved out with several changes 

 of acetone, before the tissues are immersed in the wax. 



{b) Blocks should be kept dry and stored in airtight containers 

 as the wax is liable to take up moisture from the atmosphere. 



{c) Sections can be attached to slides by means of Haupt's 

 adhesive (see pages 529-30). 



POLYVINYL ALCOHOL 



A simple method of embedding fat-containing tissues that 

 are incompatible with Carbowax, Waterwax, and other 



water-soluble waxes 



Soliitio7i required: 



Polyvinyl alcohol powder . . . . 20 gm. 



Tap water 80 ml. 



Glycerine . . . . . . . . 20 ml. 



Technique: 



1. Fix pieces of tissue as usual. 



2. Wash well in running water. 



3. Place 80 ml. of tap water in a 250 ml. beaker and heat to 

 about 80-90° C. 



4. Sprinkle the 20 gm. of polyvinyl alcohol powder, a little at 

 a time, with constant stirring, on the surface of the hot water. 



5. Still stirring, raise the temperature to boiling until all the 

 powder has gone into solution, then turn off the heat. 



6. While the solution is still warm, stir in the 20 ml. of 

 glycerine. 



503 



