From your tray, get your first test tube (labeled #1 on the tube). Place this under the outflow tract of the stopcock. Turn the stopcock towards the patient's back. This will open the manometer to the outflow tract and drain the manometer's contents into the test tube. Then turn the stopcock towards the manometer. This opens the outflow tract to the LP needle and CSF should drip into the test tube. Once one milliliter of CSF is collected, replace test tube 1 with test tube 2 and continue to collect one milliliter of fluid per test tube for the remaining tubes.