Which substance is described as an infiltration/embedding agent?

• A. Carbowax
• B. Benzene
• C. Cedarwood oil
• D. Xylene

Answer: (A)

In tissue processing, the substance that infiltrates the tissue and becomes the medium that solidifies to support a section is the embedding/infiltration agent. Carbowax, a polyethylene glycol polymer, is used as such an infiltration/embedding medium. It penetrates the tissue and provides structure for sectioning, often used in place of or with paraffin embedding. The other substances listed are clearing solvents (benzene and xylene) or a clearing agent (cedarwood oil) whose role is to render the tissue transparent and ready for embedding, not to serve as the infiltrating embedding medium. That’s why Carbowax is the correct choice.