Notes and References. 1  U.S. Senate: Reference Home > Glossary > Christmas tree bill. 2  Lardner, George (1966) The Day Congress Played Santa: A Look at the Christmas Tree Bill, Washington Post, 25 December, p. A1, A10. 3  Shribman, David (1983) It Began as a Rather Ordinary Piece of Legislation, New York Times, 9 November, p. A22.
When the individual is awake, blinking of the eyelid causes rheum to be washed away with tears via the nasolacrimal duct. The absence of this action during sleep, however, results in a small amount of dry rheum accumulating in corners of the eye, most notably in children.
Believe it or not, there's a wikipedia page about this: Eating mucus. Turns out the nose-picking part can be dangerous, causing nose-bleeds, infection, and nasal septum perforation, but there are some scientist who think eating boogers might actually be beneficial to the immune system.