I Am Legend – Richard Matheson
“Through experiments on the dead vampires he had discovered that the bacilli effected the creation of a powerful body glue that sealed bullet openings as soon as they were made. Bullets were enclosed almost immediately, and since the system was activated by germs, a bullet couldn’t hurt it. The system could, in fact, contain almost an indefinite amount of bullets, since the body glue prevented a penetration of more than a few fractions of an inch. Shooting vampires was like throwing pebbles into tar.”
