"These are watery solutions of vegetable matter, obtained by maceration, either in hot or cold water, with the assistance of ebullition. In selecting and conducting the operation the following general rules should be observed: -

"1st. Infusion should always be preferred before decoction, where the virtues of the vegetable substance reside in volatile oil, or in principles which are easily soluble; whereas, if they depend upon resino-mucilaginous particles, decoction is an indispensible operation. "2nd. The temperature employed must be varied according to the circumstances of each case, and infusion made with cold is in general more grateful but less active than one made with heat.

"3rd. The duration of the process must likewise be regulated by the nature of the substances; for the infusion will differ according to the time in which the water has been digested on the materials; thus the aroma of the plaut is first taken up, then in succession the colouring, astringent, and gummy parts.