This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Alnus nigra baccifera C. B. Rhamnus Frangula Linn. Black alder: a small tree, or shrub, with slender flexible branches, and broad roundish leaves; bearing black berries, which contain a blue juice, with two seeds in each. It is common in moist woods in several parts of England.
The internal yellow bark of this shrub is a strong cathartic, and in this intention is sometimes made use of by the common people in dropsies and other disorders: it generally operates with great violence, occasioning nauseae, sickness, gripes, and often vomiting. An in-fusion or decoction of it in water, infpiffated to the consistence of an extract, acts with greater mildness than the bark itself. It gives a deep yellow tincture both to water and spirit.
(a) Vide Neumann, Chemical works, p. 497. Marg-graf, Memoires de I'acad. roy. descienc. de Berlin, pour l'ann. 1749.
The berries also are strongly purgative; but are scarcely ever made use of, at least under their own name. In our markets, they are said to be sometimes substituted to those of buckthorn; which last may be distinguished by their green juice, and by their containing generally four seeds.