Sentence:  In February , 1959 , during the second admission to The New York Hospital , a biopsy specimen of the left gastrocnemius showed striking increase in the sarcolemmal sheath nuclei and shrunken muscle fibers in several <WSD>sections</WSD> . 
Meaning of the word marked with <WSD> tags:  a very thin slice (of tissue or mineral or other substance) for examination under a microscope