Non-coagulant fixatives are described as:

• A. Creating a gel that makes penetration by subsequent solutions difficult
• B. Always preserving morphology better than coagulants
• C. Cross-linking proteins very strongly
• D. Never used for immunohistochemistry

Answer: (A)

Non-coagulant fixatives work by forming covalent cross-links between proteins, effectively locking tissue structures in place without precipitating them into a gel. This cross-linking preserves morphology while maintaining antigenicity, which is why these fixatives are favored when immunohistochemistry is planned. Because they don’t create a gel-like coagulum, they generally allow better penetration of subsequent reagents.

The description that non-coagulant fixatives form a gel that blocks penetration describes coagulative fixatives, not non-coagulants. Therefore, the accurate characterization is that non-coagulant fixatives cross-link proteins very strongly, stabilizing tissue structure without the gel barrier.