The instrument described here fulfills the need for a satisfactory device that will accurately control the amount of insulin that is drawn into the syringe. It maintains accurate control of the prescribed units and simplifies preparation for the injection. It is compact, inexpensive, and easy to use. This device enables the patient to remove the plunger easily for cleaning and sterilizing the syringe, without changing the adjustment of the control or detaching it from the syringe. It is not an automatic injecting device.Instrument to accurately control the amount of insulin that is drawn into the syringe. A, without spring, for use when the plunger need not be retracted. B, with spring, to permit retraction of plunger.This instrument consists of (see figure, A): (1) a clasp and stop that are readily adaptable to the syringe barrel, (2) a gauge piece that can be easily attached to or removed from