Which statement describes additive fixatives?

• A. They chemically link or add themselves to tissue and change it
• B. They simply fix by dehydration
• C. They do not interact with tissue
• D. They only fix in cryoprotection

Answer: (A)

Additive fixatives preserve tissue by chemically bonding to tissue components, effectively adding to and cross-linking proteins and other macromolecules. This chemical modification stabilizes structure by forming covalent or ionic links, not merely by removing water. Classic examples are aldehyde fixatives like formaldehyde and glutaraldehyde, which create cross-links that lock tissues in place and preserve architecture, though they can alter antigen sites and affect downstream staining. This bonding-related mechanism distinguishes additive fixatives from dehydration-based processes or freezing methods, which don’t rely on forming new chemical bonds with the tissue.