Infiltration and Embedding in Paraffin Wax 39 



of bad quality, and drop the pieces into a bottle of melted [)araffin 

 in the oven. Do not apply extra heat; the temperature should not 

 exceed 53 to 54°C. When the old paraffin has amalgamated with the 

 new wax, make at least one change into new casting wax and cast 

 into blocks. 



REINFILTRATION 



Poorly infiltrated tissues can sometimes be salvaged by reinfiltra- 

 tion. This should not be attempted if there has been excessive 

 collapse of cells, a frequent result of poor infiltration. Cut the pieces 

 out of the paraffin block, trim away excess paraffin, and drop the 

 pieces into anhydrous dioxan, normal butyl or tertiary butyl alcohol, 

 xylene or chloroform. After 24 hr. at 35 °C. transfer to the 53 to 54° 

 oven and continue progressive infiltration. A vacuum oven may be 

 used for such salvage operations. 



Cast blocks should be stored under conditions that minimize 

 damage to the tissues and to the texture of the paraffin. I rim the 

 edges of the cast block so that both surfaces are flat. Store in a stout 

 manila en\elope or small cardboard box bearing adequate identifica- 

 tion data. If several blocks are stored in one container, use thin card- 

 board separators. Box containers should be stacked so that the blocks 

 lie flat. Stout enxelopes support the blocks well enough to permit 

 filing the envelopes in the vertical position in a filing cabinet. Storage 

 temperatures should be low enough to prevent bending of paraffin 

 blocks. 



