Abstract: A pressurized fluid is injected into a mass of material through at least one length of hose or other tubing of inherently resilient, elastomer material having one end closed and provided with at least one series of potential openings cut into the elastomer material along the length of the tubing so as to be normally tightly closed by reason of the resilency of the elastomer material but stretched open under the influneces of the pressurized fluid, which is introduced through the opposite end of the length of tubing. Gravity discharge of particulate material from a vessel having a hopper portion at its bottom can be effectively activated in this manner by the fluid-injection device of the invention.