Which statement about Bouin's fixative is true?

• A. It is the routine fixative
• B. It is used as best secondary fixative for cytoplasmic staining
• C. It makes lipids insoluble
• D. It Dehydrates tissue

Answer: (B)

Bouin's fixative is a specialized fixative whose composition gives excellent preservation of tissue detail, especially in the cytoplasm, when used after an initial fixation. It’s a mixture of picric acid, formaldehyde, and acetic acid. The acetic acid component helps swell and preserve cytoplasmic elements, while the picric acid promotes strong cytoplasmic contrast. Because of this, Bouin's is often used as a secondary fixative to improve cytoplasmic staining quality after a primary fixative has done the initial cross-linking. It is not the routine fixative (formalin-fixed tissues are more typical for routine processing), and it does not dehydrate tissue by itself—the dehydration steps occur during processing with graded alcohols. It also does not preserve lipids well; lipids are not a strong point of Bouin's fixation, and in practice lipids are often removed or not well preserved with this fixative. For these reasons, the statement about Bouin's being the best secondary fixative for cytoplasmic staining reflects its practical role in enhancing cytoplasmic detail.