This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
The drugs that have been grouped together under this term comprise some consisting of the entire plant (chiretta, carrageen, ergot), others of the plant from which a small portion only has been removed (aconite, lobelia, horehound), and others again that represent only a small part of the plant (Indian hemp, savin).
The characters utilised in the identification of the herbs are to a great extent the same as those that would be employed by botanists in the identification of the plant, and these characters can usually be observed if the drug be previously boiled for a few minutes in water. The details of the flowers and leaves, and the arrangement of the latter on the stem, are thus of primary importance. Difficulties are not likely to occur, except in the distinction of the drug from other nearly allied species.
Flowering herbs are commonly gathered when in flower, and dried in the shade. They should then be completely dried, and kept in airtight containers to obviate changes that are likely to ensue as the result of the action of enzymes. Such changes in some cases show themselves by changes in colour, etc, but in others they may affect and modify the active constituents without producing any visible alteration.