66 DEHYDRATION 



into water which must permeate the pieces. It is then transferred to a 

 mixture of water and methylal in equal parts, then pure methylal, then 

 methylal dehydrated in anhydrous sodium carbonate ; after these 

 baths the pieces are placed in equal parts of methylal and paraffin oil. 

 The dish is warmed up on a water bath, and then transferred to soft 

 melted paraffin, and then finally into the hard paraffin. One hour 

 for each stage is the time given by Dufrenoy, It is claimed that this 

 method does not harden tissues, and its solvent power on cell granules 

 is negligible. Methylal is rather expensive. We have had no success 

 with this method. 



