This section is from the book "Culinary Herbs", by M. G. Kains. Also available from Amazon: Culinary Herbs, Their Cultivation, Harvesting, Curing and Uses.
Rue (Ruta graveolens, Linn.).
Borage (Borago officinalis, Linn.).
Fennel-flower (Nigella sativa, Linn.).
Before dismissing this section of the subject, it may be interesting to glance over the list of names once more. Seven of these plants were formerly so prominent in medicine that they were designated "official" and nearly all the others were extensively used by physicians. At the present day there are very few that have not passed entirely out of official medicine and even out of domestic practice, at least so far as their intrinsic qualities are concerned. Some, to be sure, are still employed because of their pleasant flavors, which disguise the disagreeable taste of other drugs. But this is a very different matter.
One of the most notable of these is fennel. What wonders could that plant not perform 300 years ago! In Parkinson's "Theatricum Botanicum" (1640) its "vertues" are recorded. Apart from its use as food, for which, then, as now, it was highly esteemed, without the attachment of any medicinal qualities as an esculent, it was considered efficacious in cases of gout, jaundice, cramps, shortness of breath, wheezing of the lungs; for cleansing of the blood and improving the complexion; to use as an eye-water or to increase the flow of milk; as a remedy for serpent bites or an antidote for poisonous herbs and mushrooms; and for people who "are grown fat to abate their unwieldinesse and make them more gaunt and lanke."
But let us peep into the 19th edition of the United States Dispensatory. Can this be the same fennel which "is one of our most grateful aromatics," and which, because of "the absence of any highly excitant property,' is recommended for mixing with unpleasant medicines? Ask any druggist, and he will say it is used for little else nowadays than for making a tea to give babies for wind on their stomachs. Strange, but true it is! Similar statements if not more remarkable ones could be made about many of the other herbs herein discussed. Many of these are spoken of as "formerly considered specific" for such and such troubles but "now known to be inert."
The cause is not far to seek. An imaginative and superstitious people attached fanciful powers to these and hundreds of other plants which the intervening centuries have been unable wholly to eradicate, for among the more ignorant classes, especially of Europe, many of these relics of a dark age still persist.
But let us not gloat over our superior knowledge. After a similar lapse of time, may not our vaunted wisdom concerning the properties of plants look as ridiculous to the deliver among our musty volumes? Indeed, it may, if we may judge by the discoveries and investigations of only the past fifty years. During this time a surprisingly large number of plants have been proved to be not merely innocuous instead of poisonous, as they were reputed, but fit for human food and even of superior excellence!