To preserve tissues for further examination, what is the usual ratio of tissue to fixative used, by weight?

• A. 1 to 1
• B. 1 to 5
• C. 1 to 10
• D. 1 to 50

Answer: (C)

Achieving proper fixation hinges on allowing enough fixative to diffuse through the tissue. The usual practice is to have the tissue immersed in fixative at a 1-to-10 ratio by weight, meaning 1 part tissue and 10 parts fixative. This balance provides sufficient fixative to penetrate and preserve cellular details without leaving too little fixative to complete fixation. Using less fixative relative to tissue can lead to incomplete fixation and degradation, while using far more fixative can slow penetration and cause over-fixation artifacts. For routine processing, 1:10 is the standard approach, and if tissues are larger, they’re typically cut into smaller pieces to maintain effective fixation.