Which reagent is used immediately after fixation when processing tissue in the described schedule?

• A. 65% alcohol
• B. 10% neutral-buffered formalin
• C. Aliphatic hydrocarbon
• D. Paraffin

Answer: (A)

After fixation, the tissue still contains water that must be removed before paraffin can infiltrate. Dehydration with alcohol starts this process, so using an alcohol reagent immediately after fixation is the correct next step. The tissue is typically moved through increasing alcohol concentrations to gradually replace water with alcohol, preparing it for clearing and embedding.

The other steps occur later in the schedule: a fixative (not after fixation) would not be used here, a clearing agent (aliphatic hydrocarbon) comes after dehydration to remove alcohol and make the tissue receptive to paraffin, and paraffin is the embedding medium used after clearing.