Sentence:  After drying the sections under the fan , <WSD>fixing</WSD> in acetone , and drying at 37 ` as in the indirect method , the sections were treated with conjugated * * f or * * f ( undiluted unless mentioned otherwise ) for 5 - 30 minutes . 
Meaning of the word marked with <WSD> tags:  kill, preserve, and harden (tissue) in order to prepare for microscopic study