FOE MEDICINAL PURPOSES. 97

hops contain at the time : thus it is usual to have two kilns of dif-ferent temperatures at work at the same time. It should, however,oe observed, that the principal art of drying hops is in doing it astjuickly as possible, so as not to injure them in their colour. Assoon as they are dried, it is considered necessary to put them up intoclose and thick bags.

It should be observed, that all vegetables contain at every period°f their growth two distinct species of moisture: the one called by na-turalists the common juice, which is the ascending sap, and is repletewith watery particles : the other is termed the proper juice, which havingpassed up through the leaves, and being there concocted and deprived°f the watery part, contains the principle on which the various proper-ties and virtues of the plants depend. We therefore find that the ope-fations above described only go to this, that the watery particles inthe common juice should he evaporated, as being a part necessary tooe got rid of; and the proper juice being of a volatile nature, the lesstune the plants are exposed for that purpose, the less of this preciousmaterial will be lost : and as those parts are Hying off continuallyfrom all dried vegetables, there should be one general ride made withregard to their preparation; for, if we instance mint, balm, pennyroyal,&c., the longer these ore kept in the open air, the weaker are theyfound to be in their several parts.

From hence we may naturally infer, that the usual mode in whichthe generality of herbs are dried, is not so good for the purpose, as onewould be if contrived on similar principles, as, during the length oftime necessary for the purpose, a great deal of the piincipal parts ofthe plants must of course be evaporated and lost; for little else is re-garded than to dry them so as to prevent putrefaction. Although thegenerality of herbs met with are prepared as above described, yet in sucharticles as Digitalis, Hyoscyamus, Conium, Toxicodendron, &c, wherethe quantity necessary for a dose is so small, and so much depends onits action, practitioners are often obliged to prepare it themselves. Ishall therefore relate the following mode as the best adapted to thatpurpose. The Digitalis is prepared by collecting the leaves in thesummer, and stripping them off from the foot-stalks; these should bethen carefully exposed to a slow heat, and the watery extract slowlythrown off; in which they should not be exposed to any great degree of

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