The second finger (third digit) has the most literal meaning of all. Less commonly referred to as the long or tall finger, the digitus medius manus sits in the center of the hand, right between the digitus secondus manus and the ring finger. How the middle finger became an offensive gesture is another story altogether.
To see how the pump works, look at the drawing below. The pump consists of a small diameter pipe (called the piston) inserted into a larger diameter pipe (called the cylinder). The drawing shows the pump at two points during its operation. The top drawing shows air being drawn into the pipe by pulling out the piston. The bottom drawing shows air exiting the pipe when the piston is pushed back in. At the right end of the pipe is a commercially bought one-way valve.
Replacing fluorescent ceiling light tubes -- or those of any fluorescent fixture under cabinets or above bathroom sinks -- is accomplished in the same manner. The tricky part is figuring out how to remove the cover to access the fluorescent tube, but even this is a simple task once you know the basics.. Turn the tube one-quarter turn with your fingers and pull straight down with both hands. If the tube does not remove easily, turn one-half-turn in the opposite direction and pull again. If the tube will still not remove easily, try pushing it to one side. Some fixtures use a spring mechanism within the socket.