Sentence:  After drying the <WSD>sections</WSD> under the fan , fixing 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:  a very thin slice (of tissue or mineral or other substance) for examination under a microscope