With the subject invention, a pump may be formed that generally includes a reservoir formed to accommodate at least one fluid dose, and a fluid-collecting chamber in communication with the reservoir. The fluid-collecting chamber is located such that fluid from the reservoir is fed thereinto, preferably gravitationally. A piston is disposed to reversibly slide within at least a dose-control portion of the fluid-collecting chamber, and the piston is configured such that upon sliding within the dose-control portion, the piston seals or substantially seals the dose-control portion from other portions of the fluid collecting chamber. The piston is configured to displace a volume of fluid from the sealed or substantially sealed dose-control portion which is approximately equal to or greater than the volume of one of the doses of the pump. A nozzle is also provided which is located such that the fluid displaced by the piston from the dose-control portion is generally urged towards the nozzle.
