Sectioning 55 



2. Sections jail to form ribbons, usually due to hardness of paraffin. 



a. Use softer paraffin (lower melting point). 



b. Blow on knife to warm it or dip it in warm water. 



c. Cut thinner sections. 



d. Place table lamp near knife and block to warm it. 



e. Resharpen knife. 



/. Lessen tilt of knife, and clean edge. 



g. Dip block in softer paraffin and retrim so a layer of this paraffin 

 surrounds orioinal block. 



3. Sections are wrinkled or compressed. 



a. Resharpen knife; a dull knife compresses badly. 



b. Paraffin too soft; reimbed in harder paraffin. 



c. Cool block and knife. 



d. Increase tilt of knife. 



e. Clean edge of knife with finger or xylene, remove any paraffin 

 collected there. 



/. Tissue is not completely infiltrated,* or too much crystallization 



is present. 

 g. Soak tissue block in water,f |-1 hour or overnight if necessary. 



4. Ribbons are split or scratched longitudinally. 



a. Nick in knife; move to another part of edge or resharpen it. 

 /;. Knife dirty or gritty along edge. 



c. Dirt or hard particles in tissue or in paraffin, crystals from fixing 

 solution not adeqtiately removed. Filter paraffin, decalcify or 

 desilicify tissue. 



d. Decrease tilt of knife. 



e. Tissue too hard; soak in water. f 



5. Tissue crumbles or jails out of paraffin. 



a. Poor infiltration;* reimbed. 



b. Not completely dehydrated. 



c. Not completely dealcoholized. 



d. Too long in paraffin bath or too hot while there; soak in water.f 



e. Clearino fluid made tisstie too l^rittle- soak in wMter. 



o 



* Most conditions of poor infiltration are due to traces of water or alcohol. This will 

 have to be corrected by first removing such paraffin as is present. Soak the block in toluene 

 for 2 or 3 hours (or more); change twice, then place in absolute alcohol for 1 or more 

 hours. This should remove all traces of water. Clear again in toluene (check against milkv 

 appearance); re-infiltrate and embed. 



f When soaking in water is recommended, the cut face of the tissue is exposed to tap 

 ^\ater for I/2-I hour, or overnight for stubborn cases and when time is of no concern. The 

 author has foimd this treatment completelv satisfactorv, but some technicians advocate the 

 addition of glycerol (1 part to 9 parts water) or 60% ethyl alcohol {Leudruiii, 1944). The 

 fluid works in through the cut tissue surface and softens tough parts. Exception: Do not 

 soak nervous system tissue at any time and lymph nodes and fatty tissue only briefly. 



