The study cells, their origin, structure, function, and involvement in disease (using a microscope). Ear cytology is commonly performed to determine if an infection is present, and what type of infection it is, so that the appropriate treatment can be selected. This is done by using a cotton-tipped swab to collect a sample from the ear canal, which is then applied to a slide, stained, and examined under the microscope. Cytology can also be performed by using a needle to aspirate cells from a mass or lesion, then examining them on a slide. Often, these slides are sent to a pathologist, a board certified specialist in this area of veterinary medicine, to describe and suggest a diagnosis.