This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
This is the seed of Strychnos Ignatia, the Ignatia amara of the younger Linnaeus, a tree of moderate size, growing in the Philippine Islands. The seeds are embedded in the dry pulp of a fruit resembling a pear in size and shape.
The bean of St. Ignatius is about an inch long, of less thickness, convex on one side, obscurely angular on the other, of a pale-brown colour, externally covered with a very short down, internally translucent, hard, and horny. In its sensible properties of odour and taste, and its relations to water and alcohol, it is closely analogous to nux vomica.
Both nux vomica and the bean of St. Ignatius owe their medicinal virtues mainly to two alkaloids, denominated strychnia and brucia; and claims have been advanced to the discovery of a third, to which the name of igasuria has been given. These bases are supposed to exist naturally in combination with a peculiar acid, called igasuric or strychnic. The alkaloids differ greatly in strength, strychnia being estimated as having at least twelve times the strength of brucia, and igasuria being intermediate. For practical purposes, strychnia may be considered as the active principle, and is the only one much used in an isolated state. Though similar in virtues, nux vomica and bean of St. Ignatius probably differ greatly in power; at least, the latter contains a much larger proportion of strychnia than the former; the percentage of that alkaloid being given at 0.4 in nux vomica, and 1.2 in the bean of St. Ignatius.
Incompatibles. Alkalies, their carbonates, and alkaline earths, and the vegetable astringents, throw down precipitates from watery solutions of these medicines, the former separating the insoluble alkaloids, the latter forming insoluble tannates; but, if the precipitated matter is swallowed, it is capable of acting energetically, though probably somewhat more slowly than the solution.