Abstract: A pipetting device serves to hold and actuate a detachably mounted syringe having a syringe body and a piston. The device is provided with means for adjusting the volumetric capacity of the syringe. The device comprises two racks and a pinion which is in mesh with both said racks and operable to move them in mutually opposite directions. The racks are connected to respective sliders, one of which is connected to a rod for actuating the piston of the syringe. A single actuating lever is provided for actuating the piston and is connected to the sliders by an actuating mechanism, which comprises a positively actuated transverse slider, which constitutes a stop member and in response to an automatic resetting of the actuating lever to its initial position is moved from the path of one of said sliders into the path of the other.