Mercury, Dog's

Medical Herbs Catalogue


Mercury, Dog's

Botanical Name: Mercurialis perennis (LINN.)
Family: N.O. Euphorbiaceae

Description: Dog's Mercury, a perennial, herbaceous plant, sending up from its creeping root numerous, undivided stems, about a foot high, is common in woods and shady places throughout Europe and Russian Asia, except in the extreme north. It is abundant at Hythe in Sussex.

Each stem bears several pairs of rather large roughish leaves, and from the axils of the upper ones grow the small green flowers, the barren on long stalks, the fertile sessile, the first appearing before the leaves are quite out. The stamens and pistils are on different plants. The perianth is three-cleft to the base. The barren flowers have nine stamens or more, the fertile flowers two styles and two cells to the two-lobed ovary.

Male and female plants are rarely found intermixed, each usually growing in large patches. The female are less common than the male, and the plant increases more by the spreading of its creeping rootstocks and stems than by seed. It flowers from the end of March to the middle of May and seeds in the summer. The leaves of the male flowering plants are more pointed and less serrated than those on the female plants, which have longer stalks.

Dog's Mercury has a disagreeable odour and is extremely acrid, being poisonous to animals in the fresh state. It has been said, however, that heat destroys its harmfulness, and that it is innocuous in hay. Its chemical constituents have not been ascertained.

Dog's Mercury has proved fatal to sheep, and Annual Mercury to human beings who had made soup from it.

History: We find it spoken of in the old herbals as possessing wonderful powers, but it has been abandoned as a dangerous remedy for internal use. Culpepper speaks strongly of the 'rank poisonous' qualities of Dog's Mercury, and adds, with some contempt: 'The common herbals, as Gerarde's and Parkinson's, instead of cautioning their readers against the use of this plant, after some trifling, idle observations upon the qualities of Mercurys in general, dismiss the article without noticing its baneful effects. Other writers, more accurate, have done this; but they have written in Latin, a language not very likely to inform those who stand most in need of this caution.' It derives its name from the legend that its medicinal virtues were revealed by the god Mercury. The Greeks called it Mercury's Grass. The French call it La Mercuriale, the Italians, Mercorella. The name Dog's Mercury or Dog's Cole, was probably given it because of its inferiority from an edible point of view, either to the Annual, or Garden Mercury, or to a plant known to the older herbalists as English Mercury, which was sometimes eaten in this country and some parts of the Continent as a substitute for that vegetable. The prefix 'Dog' was often given to wild-flowers that were lacking in scent or other properties of allied species - as, for instance, Dog Violet, Dog Rose, etc.

That Dog's Mercury has been eaten in mistake for Good King Henry, with unfortunate results, we know from the report of Ray, one of the earliest of English naturalists, who relates that when boiled and eaten with fried bacon in error for this English spinach, it produced sickness, drowsiness and twitching. In another instance, when it was collected and boiled in soup by some vagrants, all partaking of it exhibited the ordinary symptoms of narcotic and irritant poisoning, two children dying on the following day.

The fact that some old books recommend Dog's Mercury as a good potherb arose probably from confusing it with the less harmful annual species, called by Gerard the French or Garden Mercury.

Medicinal Action and Uses: Hippocrates commended this herb for women's diseases, used externally, as did also Culpepper, who says it is good for sore and watering eyes and deafness and pains in the ears. He advises the use of it, also, as a decoction, 'made with water and a cock chicken,' for hot fits of ague. It has been employed for jaundice and as a purgative.

The juice of the whole plant, freshly collected when in flower, mixed with sugar or with vinegar, is recommended externally for warts, and for inflammatory and discharging sores, and also, applied as a poultice, to swellings and to cleanse old sores.

A lotion is made from the plant for antiseptic external dressings, to be used in the same manner as carbolic.

The juice has also been used as a nasal douche for catarrh.

When steeped in water, the leaves and stems of the plant give out a fine blue colour, resembling indigo. This colouring matter is turned red by acids and destroyed by alkalis, but is otherwise permanent, and might prove valuable as a dye, if any means of fixing the colour could be devised. The stems are of a bright metallic blue, like indigo, and those that run into the ground have the most colouring matter.