If a ribbon splits while cutting paraffin sections, the trouble is most likely due to

• A. Nicks in the blade edge
• B. Dull knife edge
• C. Improper embedding medium
• D. Excess moisture in paraffin

Answer: (A)

Ribbons splitting during microtomy points to a disruption along the cutting edge of the blade. A nick in the blade edge creates a small irregularity that acts as a weak point, so as the tissue is advanced and sheared, the section can fracture at that damaged spot, producing a split ribbon. A dull knife tends to cause tearing or chatter rather than cleanly splitting the ribbon. Improper embedding medium would affect support and section integrity in other ways (crumbling or poor adherence), and excess moisture in paraffin tends to cause sections to be sticky or warp rather than produce a split ribbon. Check the blade for nicks and replace or hone as needed to restore a smooth edge.