Please refer to the following paragraph of the paper: (how to quickly exhaust the air under the Mao's dropper when the liquid is empty - Chinese Journal of Rural Medicine)
"When the infusion of liquid is inadvertently liquid is empty, the level of liquid drops below the "dropper", after changing the liquid due to the "dropper". We found that the liquid away from the empty, from the infusion bottle to pull down the infusion needle, slowly down, so that the infusion tube "dropper" the upper part of the liquid slowly back to the bottom of the dropper and "dropper" the lower part of the tube, and then quickly close the regulator clip, the infusion needle into the new Then quickly close the adjusting clip, insert the infusion needle into the new infusion bottle, squeeze the dropper to make the liquid level in the appropriate position, and open the adjusting clip to continue to enter the liquid. This method in the liquid change at the same time can quickly exhaust despite the internal empty gas, to ensure the smooth input of liquid."