What happens to tissue with extended sitting in melted paraffin?

• A. It shrinks and hardens
• B. It swells and softens
• C. It expands
• D. It dissolves

Answer: (A)

When tissue is left in melted paraffin for an extended time, it tends to shrink and become hard. The heat of the paraffin (around 60°C) drives out remaining moisture and allows the paraffin to infiltrate into tissue spaces. As the tissue cools and the wax solidifies around it, the spaces become filled with wax and the tissue contracts slightly, leading to shrinkage. The combination of wax replacement for water and the solidification of the wax also makes the tissue more rigid or brittle. This is not a situation where the tissue would swell or soften, and paraffin does not dissolve tissue; it rather consolidates and dries the sample, producing a hard, shrunken block.