A fan includes a plurality of blade portions arranged spaced apart from each other in a circumferential direction, each blade portion having a blade surface including a pressure surface disposed on a rotational direction side of the fan and a suction surface disposed on a back side of said pressure surface. Thus, the pH of a solution can be adjusted easily and accurately, by precisely controlling a constant current, a constant voltage, and current and voltage application times, thereby enabling useful application in various biological assays such as cell lysis. While the tool is inside the blood vessel, the position of the tool is determined.