Abstract: For an endoscopic resection or examination of a body cavity or joint where a physiological liquid is pumped at one location to a joint from a feed conduit connected to a feed pump and withdrawn at another location from the joint through a suction conduit connected to a suction pump, this suction pump is operated at a rate corresponding to a generally constant low rate of flow in the suction conduit and the feed pump is operated in accordance with the pressure detected in the joint to maintain the pressure above a predetermined desired level. Furthermore when a tool carrying one end of an auxiliary suction conduit is inserted into the joint so that periodically this conduit can be connected to the pump so that liquid can be withdrawn from the joint through this auxiliary conduit, the method comprises the step of automatically increasing the suction-pump rate when the auxiliary conduit is connected to the suction pump to a predetermined relatively high rate.