Chemically, the toxic action of Hemlock depends on its alkaloids, "coniine," and "methyl-coniine."
Vinegar has proved useful in neutralising the poisonous effects of Hemlock, and it is said if the plant is macerated or boiled in vinegar it becomes altogether inert.
For inhalation to subdue whooping-cough, three or four grains of the extract should be mixed with a pint of boiling water in a suitable inhaler, so that the medicated vapour may be inspired through the mouth and nostrils.
To make a Hemlock poultice, when the fresh plant cannot be procured, mix an ounce of powdered hemlock leaves (from the druggist) with three ounces of linseed meal; then gradually add half a pint of boiling water whilst constantly stirring.
Herb gatherers sometimes mistake the wild Cicely (Myrrhis odorata) for the Hemlock; but this Cicely has a furrowed stem without spots, and is hairy, with a highly aromatic flavour. The bracts of Hemlock, at the base of the umbels, go only half way round the stem. The rough Chervil is also spotted, but hairy, and its stem is swollen below each joint. Under proper medical advice, the extract and the juice of Hemlock may be most beneficially given internally in cancer, and as a nervine sedative.
The Hemlock was esteemed of old as Herba Benedicta, a blessed herb, because "where the root is in the house [251] the devil can do no harm, and if anyone should carry the plant about on his person no venomous beast can harm him." The Eleusinian priests who were required to remain chaste all their lives, had the wisdom to rub themselves with Hemlock.
Poultices may be made exclusively with the fresh leaves (which should be gathered in June) or with the dried leaflets when powdered, for easing and healing cancerous sores. Baron Stoerck first brought the plant into repute (1760) as a medicine of extraordinary efficacy for curing inveterate scirrhus, cancer, and ulcers, such as were hitherto deemed irremediable.
Likewise the Cicuta virosa, or Water Hemlock, has proved curative to many similar glandular swellings. This is also an umbelliferous plant, which grows commonly on the margins of ditches and rivers in many parts of England. It gets its name from cicuta (a shepherd's pipe made from a reed), because of its hollow stems. Being hurtful to cows it has acquired the title of Cowbane.
The root when incised secretes from its wounded bark a yellow juice of a narcotic odour and acrid taste. This has been applied externally with benefit for scirrhous cancer, and to ease the pain of nervous gout. But when taken internally it is dangerous, being likely to provoke convulsions, or to produce serious narcotic effects. Nevertheless, goats eat the herb with impunity:—
"Nam videre licet pinguescere soepe cicutam,
Barbigeras pecudes; hominique est acre venenum."