A palm-held device is disclosed for injection of a substance into an organism. The palm-held device has the shape of a computer mouse, and so is very familiar, which helps with ease-of-use and comfort. Like a computer mouse, the device can be moved easily by gently holding and guiding the mouse with the fingers and the palm of the hand. There are many possible button configurations, such as a single button mouse, the button having a large surface at the front top portion of the mouse, and being pressable by any finger. There can also be a two button mouse, such that the left button actuates the injection, and the right button is the “safety” that allows the left button to actuate the injection. The two buttons can be on the top front of the mouse, or can be on the right and left sides of the mouse.