Surgeons using a split beam" operating microscope to remove a brain tumour. The microscope is wrapped in plastic to maintain sterile conditions, & allows the surgeons a view of the same illuminated field: it is also fitted with a video camera so that students may follow the course of the operation. The surgeon at left is using an ultrasound probe to liquify and remove the tumour. Ultrasonic vibrations emulsify the growth, allowing it to be sucked away. Furthermore, tissue is removed from its centre, causing the growth to collapse in on itself, and allowing any remaining tumour matter to be more easily teased away from surrounding healthy tissue."