WdU'Y-Solublc nV/.v Enihcddiiig (Uid Scctioiiing 81 



Infihraiion and Embedding: carbowax \-i hours, 50-56°C; agitate 

 occasionally. 



Prepare the carbowax ahead ot time by placing the mixture in a 

 beaker and allo\\ ing it to melt in an oven. If it is melted rapidly over a 

 flame, a block formed from it \\'\\\ not cut well. The mixture will 

 keep for an indefinite time in the oven. 



Embed by placing the tissue in a second batch of carbow^ax in a small 

 container or paper box in the refrigerator luitil it is hard, approximately 

 30 minutes. Blocks solidified at room temperature will not section as 

 well as those made in the refrigerator. Do not chill blocks in water — it 

 dissolves carbowax. When completely hard, the blocks may be removed 

 from the refrigerator and will turn opaque as they ^varm to room tem- 

 perature. This is of no disadvantage, but keep them in polyethylene or 

 cellophane bags or containers if storing them for some time. They must 

 not pick up water, even from the atmosphere. 



Sectioning: A cool dry room is recommended. The edges of the block 

 must be parallel in order to obtain ribbons. Wade (1952) suggests that 

 if the sections do not adhere, if they break up on handling or do not 

 ribbon at all, try exposing the block to air for a day or t^vo. For immedi- 

 ate tise, try paintmg a 25% solution of beeswax in chloroform on the 

 upper and lower surfaces of the block. Make the layer uniform and 

 allow it to become dull dry. Such surfaces should help the sections ad- 

 here to each other. Plain water may do as well in some cases. 



Hale [1952) found that variable and high humidity produces erratic 

 results, because with the absorption of ^^■ater on the surfaces of the 

 block sectioning becomes impossible. He found that at 24-25 °C sections 

 ceased to ribbon at 40% humidity; at 17-18^C humidity had no effect. 

 He, therefore, concluded that, as the temperature drops, greater hu- 

 midity is permissible. At higher temperatures, a higher percentage of 

 hard w^ax may be used, btit care must be taken that the block does not 

 become too brittle for good sectioning. 



Motmting Sections: AV^ater mounting dissolves carbowax, and ^vill 

 restilt in distorted sections and surface tension problems when trying to 

 affix sections to slides. \'ariotis solutions for this problem follow. 



Blank and McCarthy (1950) Method 



potassium dichromate 0.2 gm. 



gelatine 0.2 gm. 



distilled water 1000.0 ml. 



Boil for 5 minutes. Eilter. 



