Chapter 3 



Clearing, Infiltrating, 

 and Embedding for 

 the Paraffin Method 



Clearing 



In most technics that require dehydration and infiltration, an inter- 

 mediary step is necessary to hurdle the transition between the two. Be- 

 cause the alcohol used for dehydration ^vill not dissolve or mix with 

 paraffin (exception, tertiary butyl alcohol as noted previously) some 

 fluid miscible with both alcohol and paraffin must be used before infil- 

 tration can take place. 



The hydrocarbons benzene, toluene and xylene are reagents com- 

 monly used for this purpose, but if the tissue contains considerable 

 cartilage, or is fibrous or muscular, thus tending to harden readily, 

 sometimes it is wise to avoid these solutions. Xylene, formerly one of 

 the most widely used reagents, is the worst offender of the three in this 

 connection, and in most cases of clearing for infiltration it should be 

 abandoned in favor of one of the other two. Benzene presents fe^ver 

 hardening problems than either of the others, but because of its low 

 boiling point (80°C) sometimes is difficult for beginners to use. If a 



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