a movable mixing disc is inserted into a regular syringe . the mixing disc has a small hole covered by a fine screen , allowing only saline solution to get behind the disc . when the plunger of the syringe is pressed , the saline solution emerges from the mixing disc hole as a high velocity jet , stirring up the settled particles . as the ejection continues , the mixing disc is pushed forward by the plunger in order to eliminate any unused volume .