Palko's Medical Laboratory Procedures 3rd Edition by Danielle Wilken, Phyllis Cox

Exercise 57

Melissa performs some blood cell differential counts under the oil-immersion objective of the laboratory’s binocular microscope. She has to leave the microscope, and while she is gone, Susan (a coworker) views urines under the l0X and 40X objectives. When Melissa tries to resume her blood-cell differential work, she finds that she cannot bring one of the oculars into focus. What is the problem? How can it be solved?