This section is from the book "Materia Medica And Therapeutics: An Introduction to the National Treatment of Disease", by John Mitchell Bruce. Also available from Amazon: The pharmacology and therapeutics of the materia medica.
The cinchona barks contain but a small percentage of alkaloids, and are far too bulky for use as antiperiodics and antipyretics if quinia can be obtained. They are therefore given only as bitter stomachics and tonics. The amount of tannin contained in them indicates that they may be used when an astringent effect is also desired, either locally, as in passive diarrhoea, or remotely, as in sweating, chronic mucous discharges, and purulent formations; and avoided in constipation, dyspepsia, or irritability of the bowels. The red bark is especially astringent.
Cinchonia, and other non-officinal alkaloids and products of bark, may be employed as substitutes for quinia, their action being very similar. Cinchonia is from 1/3 to 1/2 as powerful as quinia.