Minor snit, but tree bark does not contain aspirin; it contains salicylic
acid. Aspirin is acetylsalicylic acid, which decomposes into salicylic
acid in the presence of water. While salicylic acid *is* the active
ingredient, it can cause chemical burns to the esophagus and mouth when
concentrated to any degree. The acetyl- group replaces the hydroxyl group
just long enough to get it into your stomach with damaging the tissue along
the way. Aspirin is basically a technological improvement on a very old
analgesic.
-James Rogers
jamesr@best.com