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|Conium maculatum in California|
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Conium maculatum (hemlock or poison hemlock) is a highly poisonous biennial herbaceous flowering plant in the carrot family Apiaceae, native to Europe and North Africa. A hardy plant capable of living in a variety of environments, hemlock is widely naturalized in locations outside its native range.
Conium maculatum is known by several common names. In addition to the English hemlock, the Australian carrot fern, and the Irish devil's bread or devil's porridge the following names are also used: poison parsley, spotted corobane and spotted hemlock.
The plant should not be confused with the coniferous tree Tsuga, also known by the common name hemlock even though the two plants are quite different. The dried stems are sometimes called kecksies or kex.
Conium maculatum is a herbaceous biennial flowering plant that grows to 1.5–2.5 m (5–8 ft) tall, with a smooth, green, hollow stem, usually spotted or streaked with red or purple on the lower half of the stem. All parts of the plant are hairless (glabrous); the leaves are two- to four-pinnate, finely divided and lacy, overall triangular in shape, up to 50 cm (20 in) long and 40 cm (16 in) broad.
The flowers are small, white, clustered in umbels up to 10–15 cm (4–6 in) across. When crushed, the leaves and root emit a rank, unpleasant odor. It produces a large number of globular fruits that allow the plant to form thick stands in modified soils.:818:180
Distribution and ecology
Conium maculatum is native in temperate regions of Europe, West Asia, and North Africa. It has been introduced and naturalised in many other areas, including Asia, North America, Australia, and New Zealand. It is often found on poorly drained soils, particularly near streams, ditches, and other surfaces water. It also appears on roadsides, edges of cultivated fields, and waste areas. It is considered an invasive species in 12 U.S. states.
Conium maculatum grows in damp areas, but also on drier rough grassland, roadsides, and disturbed ground. It is used as a food plant by the larvae of some Lepidoptera species, including silver-ground carpet. Poison hemlock flourishes in the spring, when most other forage is gone. All plant parts are poisonous, but once the plant is dried, the poison is greatly reduced, although not gone completely.
Biochemistry of the alkaloid toxins
Conium contains the piperidine alkaloids coniine, N-methylconiine, conhydrine, pseudoconhydrine, and gamma-coniceine (or g-coniceïne), which is the precursor of the other hemlock alkaloids.
Uses and effects
Coniine disrupts the workings of the central nervous system through inhibitory action on nicotinic acetylcholine receptors. In high enough concentrations, coniine can be dangerous to humans and livestock. Due to high potency, the ingestion of seemingly small doses can easily result in respiratory collapse and death.
Coniine causes death by blocking the neuromuscular junction in a manner similar to curare; this results in an ascending muscular paralysis with eventual paralysis of the respiratory muscles which results in death due to lack of oxygen to the heart and brain. Death can be prevented by artificial ventilation until the effects have worn off 48–72 hours later. For an adult, the ingestion of more than 100 mg (0.1 gram) of coniine (about six to eight fresh leaves, or a smaller dose of the seeds or root) may be fatal.
Coniine also has significant toxic effects on the kidney. The presence of rhabdomyolysis and acute tubular necrosis was shown in patients who had died from hemlock poisoning. A fraction of these patients were also found to have acute renal failure.
This section needs expansion with: coverage of the plentiful examples of human accidental and intentional poisonings. You can help by adding to it. (January 2017)
On other animals
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Conium maculatum is poisonous to animals. In a short time, the alkaloids produce a potentially fatal neuromuscular blockage when the respiratory muscles are affected. Acute toxicity, if not lethal, may resolve in the spontaneous recovery of the affected animals provided further exposure is avoided.
It has been observed that poisoned animals tend to return to feed on this plant. Chronic toxicity affects only pregnant animals. When they are poisoned by C. maculatum during the fetus' organ formation period, the offspring is born with malformations, mainly palatoschisis and multiple congenital contractures (MCC; frequently described as arthrogryposis). Chronic toxicity is irreversible and although MCC can be surgically corrected in some cases, most of the malformed animals are lost. Such losses may be underestimated, at least in some regions, because of the difficulty in associating malformations with the much earlier maternal poisoning.
Since no specific antidote is available, prevention is the only way to deal with the production losses caused by the plant. Control with herbicides and grazing with less susceptible animals (such as sheep) have been suggested. C. maculatum alkaloids can enter the human food chain via milk and fowl.
Historical and cultural references
This section needs expansion with: other cultural and historical aspects, including its recognition and use in medieval times, its appearance in modern fiction, etc.. You can help by adding to it. (January 2017)
In ancient Greece, hemlock was used to poison condemned prisoners. The most famous victim of hemlock poisoning is the philosopher Socrates. After being accused of impiety and corrupting the young men of Athens, in 399 BC, his trial (where he easily refuted these charges) resulted in his being condemned to death. Socrates was given a potent infusion of the hemlock plant. Plato described Socrates' death in the Phaedo:
The man...laid his hands on him and after a while examined his feet and legs, then pinched his foot hard and asked if he felt it. He said "No"; then after that, his thighs; and passing upwards in this way he showed us that he was growing cold and rigid. And then again he touched him and said that when it reached his heart, he would be gone. The chill had now reached the region about the groin, and uncovering his face, which had been covered, he said – and these were his last words – "Crito, we owe a cock to Asclepius. Pay it and do not neglect it." "That," said Crito, "shall be done; but see if you have anything else to say." To this question he made no reply, but after a little while he moved; the attendant uncovered him; his eyes were fixed. And Crito when he saw it, closed his mouth and eyes.
Although many have questioned whether this is a factual account,[who?] it is the perspective of Bloch that careful attention to Plato's words, modern and ancient medicine, and other ancient Greek sources point to the above account being consistent with Conium poisoning.[better source needed]
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- "poison hemlock, spotted hemlock – Conium maculatum". Map, where regarded invasive. National Park Service. Retrieved 2009-01-14.
- Stephen T. Lee; Benedict T. Green; Kevin D. Welch; James A. Pfister; Kip E. Panter (2008). "Stereoselective potencies and relative toxicities of coniine enantiomers". Chemical Research in Toxicology. 21 (10): 2061–2064. doi:10.1021/tx800229w.
- Reynolds, T. (June 2005). "Hemlock Alkaloids from Socrates to Poison Aloes". Phytochemistry. 66 (12): 1399–1406. PMID 15955542. doi:10.1016/j.phytochem.2005.04.039.
- Vetter, J. (September 2004). "Poison Hemlock (Conium maculatum L.)". Food and Chemical Toxicology. 42 (9): 1373–1382. PMID 15234067. doi:10.1016/j.fct.2004.04.009.
- "Conium maculatum TOXINZ - Poisons Information". www.toxinz.com. Retrieved 2017-05-29.
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- "Plato, Euthyphro, Apology, Crito, Phaedo". Retrieved 2012-07-06.
- Plato, Phaedo 117e–118a. Translated by Loeb Classical Library (1990 ed.). Cambridge, MA: Harvard University Press. pp. 401–3.
- Bloch, E. (March 2001). "Hemlock Poisoning and the Death of Socrates: Did Plato Tell the Truth?". Journal of the International Plato Society (1). Archived from the original on 2017-04-07.—A version of this article was also printed in Bloch, E. (2001). Brickhouse, Thomas C.; Smith, Nicholas D., eds. The Trial and Execution of Socrates: Sources and Controversies. New York: Oxford University Press. ISBN 978-0-19-511980-0.
|Wikisource has the text of the 1905 New International Encyclopedia article Hemlock.|
- "Conium". USDA Agricultural Research Service, Germplasm Resources Information Network−GRIN.
- "Conium". Flora Europaea. Royal Botanic Garden Edinburgh.
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