The oily alkaloid Coniine or rather its source Poison Hemlock (Conium maculatum) has been long recognised for its toxicity. 'Socrates' in Ancient Greece famously committed suicide in 399BC using a potent drink made from Hemlock. It was then considered a humane method of execution. Several species of Hemlock are relatively common in the wild. These include Poison Hemlock and Water Hemlock (Cicuta virosa).
Coniine is a piperidine alkaloid, (based on the piperidine structure). It's effects are similar to that of Nicotine (a pyrrolidine alkaloid). Firstly, it causes stimulatory effects giving a feeling of well-being but quickly induces depression of the nervous system. Nicotine is quite weak in this respect. Nicotine poisoning can occur but only by excessive ingestion (smoking excessively for a long period) to "feed" the addiction (relieve the depressive effects temporarily). However, Coniine will severely depress the nervous system and can lead to paralysis and fatality, if not flushed out of the body. Other chemicals present include the piperidine alkaloid coniceine (oxidised form of Coniine) and conidrine.
Children are most at risk from poisoning. Their immune systems are not as developed and the plant is easily mistaken for other things. Belonging to the Apiaceae family, Poison Hemlock is closely related to Carrots, Parsnips, Cow Parsley, Parsley and Caraway. It has a fat tap root, very similar feathery leaf fronds and the seeds appear very much like Caraway seeds. Only when it matures do tall unmistakeable flower stalks appear with clusters of white flowers. The only sure method of distinction is in damaging the plant. When bruised it will give off an extremely pungent odour, reportedly reminiscent of mice. It has therefore also been given the names, Poison Stinkweed and Stinking Hemlock.