An adjusting device for adjusting a projecting direction of a view comprises the following components. The device effectively mixes the confluent streams with electrokinetic flow, and to a lesser degree, with pressure driven flow. Control of the peripheral device is subject to the apparatus. Such varying of the velocity allows for reducing the total forces applied to the pneumatic carrier during passage through the system. The cuvette of the digester is divided into sections by transverse walls, which are provided with communication openings in the lower part thereof.