Digestion resembles maceration, except that the process is assisted by
a gentle heat. The ingredients are placed in a flask, such as salad
oil is sold in, which should be fitted with a plug of tow or wood, and
have a piece of wire twisted round the neck. The flask is held by
means of the wire over the flame of a spirit lamp, or else placed in
some sand warmed in an old iron saucepan over the fire, care being
taken not to place more of the flask below the sand than the portion
occupied by the ingredients.