This section is from the book "A Guide To The Poisonous Plants And Weed Seeds Of Canada And The Northern United States", by Robert Boyd Thomson, H. B. Sifton. Also available from Amazon: A guide to the poisonous plants and weed seeds of Canada and the northern United States.
Other Common Name: Spotted Parsley. The poisonous effects of Conium maculatum, a plant introduced from Europe, were known long before the beginning of botany as a science. The juice, made famous on account of its connection with the death of Socrates, was used by the ancient Greeks for the execution of criminals. The poisonous principle (coniin) is found in all parts of the plant. It is particularly abundant in the leaves at flowering time, and is plentiful in the seeds, especially when green. During the spring the roots are almost harmless, but they become very poisonous in the summer. The coniin is a volatile alkaloid, and thus Poison Hemlock plants dried in hay are not very dangerous.
The symptoms are a gradual loss of muscular power, owing to paralysis of the motor nerve centre. Convulsions are not present and the mind usually remains clear until death, which results from paralysis of the lungs. Horses, in addition to the above symptoms, exhibit nausea, intermittent sweating, muscular tremors and increased rates of pulse and respiration. In cattle also the pulse is accelerated and there is salivation, bloating and great pain. A small quantity is sufficient to produce marked effects. The plant has a disagreeable odour and is coarse and unattractive when full grown. In early summer, however, the leaves are succulent and are sometimes eaten by grazing animals.
Fig. 16. - Poison Hemlock - Conium maculatum.
Chesnut recommends the following treatment: "Use of the stomach pump or emetics, tannin, tea, oak bark, stimulants, warmth at the extremities, artificial respiration and the subcutaneous injection of atropin."
The plant, though introduced from Europe, is found throughout the east to the Great Lake region, and again in the mountains of the west. It is an erect, biennial, branching plant, two to six feet tall, with a hollow stem spotted with purple. The leaves are large and pinnately decompound, with much-dissected leaflets, the ultimate divisions resembling parsley in appearance. The flowers are small and white, in large compound umbels. The fruit is smooth, ovate and flattened, with prominent, wavy ribs. It has no oil ducts. The tapering root is about an inch in diameter and has an odour like that of parsnip. The rest of the plant, when crushed, produces the characteristic foetid odour of coniin.