Hanging drop preparation used for?

Trichomonas vaginalis REF: Koss' diagnostic cytology and its histopathologic bases: Volume 1 - Page 274, American journal of obstetrics and gynecology: Volume 77 "The best way to recognize Trichomonas is the hanging drop technique in which a drop of vaginal secretion is placed on a side and is examined under the microscope" The recognition of Trichomonas is based on the motility of the protozoa and the mobility of the undulating membrane. Two methods were used in control studies: the hanging-drop technique, and the routine cytological smears