The New International Encyclopædia/Hemlock

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HEMLOCK (AS. hemlic, hymblicæ, hemlock), Conium. A genus of plants of the natural order Umbelliferæ, the members of which have compound umbels of small white flowers, small involucres and involucels, the former consisting of several small leaflets, the latter of three leaflets all on one side; the limb of the calyx merely rudimentary, and a compressed ovate fruit with five prominent wavy ridges and no vittæ. The best known and only important species is the common or poison hemlock (Conium maculatum), which grows by waysides on heaps of rubbish, and in other similar situations throughout Europe, in some parts of Asia, and naturalized in North America and Chile. It has a root somewhat resembling a small parsnip; a round, branched, hollow, bright-green stem, two to seven feet high, generally spotted with dark purple; large tripinnate, dark shining green leaves with lanceolate pinnatifid leaflets. All parts of the plant are destitute of hairs. The whole plant has a nauseous smell, particularly if rubbed or bruised. The leaves and fruits are employed in medicine. The leaves should be gathered just before the time or at the commencement of flowering, and after the removal of the larger stalks they should be quickly dried by a heat not exceeding 120°. As, however, they sometimes yield little or none of the active principles in the plant, the fresh leaves are preferred. The whole plant contains the active principles, and many fatal cases of poisoning have been attributed to eating the roots under the mistaken idea that they were parsnips.

The uses of hemlock in medicine are few and unimportant and depend chiefly upon its action upon the motor nerves, beginning with their end-organs. Although large doses cause complete paralysis by their action upon the peripheral nerves, sensation and consciousness are not affected; death finally occurs by extension of the paralysis to the muscles of respiration. In large or poisonous doses it sometimes gives rise to coma, and sometimes to convulsions or violent delirium. Among the ancient Greeks poisoning by hemlock was a common mode of death for condemned criminals, but whether it was the juice of the common hemlock or the water-hemlock that was used is unknown. The strength of its preparations is very variable, as its active principles are volatile. Practically the only use of the drug is in tetanus, hydrophobia, strychnine poisoning, and other convulsive disorders. Even in these it is rarely used, and only to prevent exhaustion by lessening muscular contractions. Water-hemlock, or cowbane (Cicuta virosa), is also an umbelliferous plant, of a genus having vaulted umbels, a live-toothed calyx, and almost globose fruit, each carpel with five broad flattened ribs and evident single vittæ. Water-hemlock grows in ditches, the margins of ponds, and wet grounds in Europe and the north of Asia. It has a large fleshy while root, covered externally with fibres; an erect much-branched stem, two to five feet high; tripinnate leaves, with linear-lanceolate regularly and sharply serrated leaflets, one general involucre or only a single small leaflet, partial involucres of many short narrow leaflets, and white flowers. It is a virulent narcotic acrid poison. Another species, Cicuta maculata, is common in North America, growing in many places. It has a spotted stem, like that of true hemlock, the name of which it very generally receives in North America. The leaves are triternate, the leaflets ternate. It is a very poisonous plant, and is the cause of many deaths. Cicuta, in Latin, seems to have been the name of the same plant called concion by the Greeks, but it is not known whether this or the previous plant was so denominated. See Coniine.