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 are grouped together under the above heading are mixtures of resins with volatile oils or oily liquids. They are secreted in schizogenous or schizolysigenous ducts which may be of either normal (Canada turpentine, copaiba) or pathological (balsam of Peru, storax) origin.
All of the constituents may vary considerably in their composition. Those oleo-resins which contain benzoic or cinnamic acid are frequently termed ' balsams.'