This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Anacardium: a moderately large kind of nut; whose kernel is covered by two tough rinds; betwixt which is lodged a fungous substance, containing in its cells an extremely acrid matter, in a liquid state when the nut is fresh, though often by long keeping growing dry. It is the produce of certain large Indian trees, of the class of the prunifera of Ray.
1. Anacardtum Ph. Paris. Anacardium orientale. Anacardium or Malaca bean: externally of a shining black colour, of the shape of a heart flattened, with a very thick pedicle occupying almost the whole basis. The tree, which is found only in the East Indies, is called by Ray arbor indica fructu conoide cortice pulvi-nato nucleum unicum nullo ossculo tectum claudente. It is thought to be the Avicennia germinans of Linnaeus.
2. Acajou, Cajous, Anacardium occidentale. Occidental anacardium or cashew nut: externally of a greyish or brownish colour, of the shape of a kidney, somewhat convex on one side, and depressed on the other. The tree, a native both of the East and west Indies, is called by Ray pomifera seu potius prunifera indica, nuce reniformi summo porno innoscente, the Indian tree bearing a fruit like an apple, with a kidney-shaped nut growing on the top of the apple; or rather with an apple growing between the nut and its pedicle, for the nut, as he observes, is produced first. It is the Anacardium occidentals of Linnaeus.
* (a) Bergius mentions having frequently prescribed with success an emulsion of bitter almonds in intermittents, in the quantity of a pint or two daily during the intermission; and asserts that it had sometimes cured where the bark had failed. Mat. hied. p. 412.
These nuts have been commended by some as possessing great medicinal virtues, and condemned by others as very dangerous. The kernels appear to have no hurtful quality: they are said to be eaten by the Indians, have a pleasant sweetish taste, yield an insipid oil upon expression, form an emulsion with water, and are apparently of the same nature with sweet almonds. The acrid juice lodged between the rinds is strongly corrosive, and is said to be used by the Indians for consuming fungous flesh, and for destroying the sensibility of aching hollow teeth. The juice is recommended by some against freckles, and other cutaneous deformities; which it removes only by excoriating the part: Geoffroy cautions against the too free application of this cosmetic, and relates that he has seen erysipelases break out all over the face from the imprudent use of it.