A device for exposing sample bodies to a fluid. The sample bodies have an active surface section that defines a measuring plane. The device includes a container, a sample body holder, and an agitating element. The container, which extends along a longitudinal axis, has an inlet, an outlet, a closed side wall, which extends along the longitudinal axis, and first and second end faces that extend transverse to the longitudinal axis. The sample body holder extends transverse to the longitudinal axis and holds at least one sample body so that its measuring plane extends perpendicular to the longitudinal axis in a first sample plane its active surface section faces away from the first end face. The agitating element driven in a rotating manner in a plane perpendicular to the longitudinal axis and is arranged on the side facing away from the first end face of the first sample plane.