Sentence:  <WSD>Microscopic</WSD> studies of the gastrocnemius , pectoralis major , transversus abdominis , biceps brachii , and diaphragm showed atrophy as well as varying degrees of injury ranging from swelling and vacuolization to focal necrosis of the muscle fibers . 
Meaning of the word marked with <WSD> tags:  of or relating to or used in microscopy