A liquid injector for use in a medical respirator having a cylinder mounted for movement within a cavity. The cavity has a supply of liquid thereto and as the cylinder moves therethrough, it entraps a quantity of liquid within the cylinder at the point when it is sealed against a closure within the cavity. A member is mounted for movement within the cylinder so that when the cylinder is moved against the closure, the member will be forced to move so as to eject the liquid entrapped therein into the stream of gas.
