1. APPARATUS FOR DISPENSING A PREDETERMINED QUANTITY OF LIQUID ON ACTUATION BY AN EXTERNAL DEVICE, SAID APPARATUS COMPRISING A SUBSTANTIALLY VERTICAL CYLINDER, MEANS FOR SUPPLYING SAID CYLINDER WITH LIQUID TO A PREDETERMINED LEVEL, A PISTON FREELY MOVABLE IN SAID CYLINDER, A LEVER ADAPTED TO BE SWUNG BY THE ACTION OF THE SAID EXTERNAL DEVICE, A PISTON ROD CONNECTED AT ONE END TO SAID PISTON AND AT THE OTHER END TO THE SAID LEVER, A HOUSING ENCLOSING SAID CYLINDER AND SAID PISTON AND ADAPTED TO RECEIVE LIQUID OVERFLOWING SAID CYLINDER, AND OUTLET MEANS IN SAID HOUSING ADAPTED TO ALLOW OUTFLOW OF SAID OVERFLOWED LIQUID BUT TO PREVENT ENTRY OF EXTRANEOUS MATTER.