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Tea is sometimes dangerous, and especially when it is allowed to stew on the fire for hours at a time. Besides _theine_, which is the stimulating, active part of it, and which is a bracing tonic to the nerves, _tannin_ is also found therein. When meat is taken with a large amount of _tannin_, the latter acts on the meat exactly as it does on hides in a tanning factory. It forms a substance resembling leather, which taxes the powers of the strongest digestion.