During the Hellenistic period (323-31 BC), the lethal characteristics of the plant poison hemlock were well known and used as a means of execution in ancient Greece. Socrates died in 399 BC, and based on the reports from those who witnessed his death, he exhibited symptoms of coniine poisoning. This alkaloid neurotoxin, coniine, causes death by muscular paralysis resulting in asphyxiation. Breathing happens because the diaphragm and muscles of the rib cage and abdomen work in concert to ensure that air reaches the lungs. The diaphragm contracts during inspiration, allowing air to move into the lungs, while the other muscles between the ribs and those in the abdomen help push air out during expiration. Automatic signals from the brain take care of this ‘behind the scenes’ task—no conscious thinking required. But when these muscles are paralyzed, breathing stops—respiratory arrest.
Poison hemlock (Conium maculatum) is a member of the carrot family (Apiaceae). Delicate fernlike leaves and lovely white umbels—the parasol-shaped flowers—make for a pretty picture in fields of damp soil, while a solid white taproot anchors the tall (2 m) plant in the ground. Originally from Europe, the plant is now widespread.
Water hemlock (Cicuta virosa) is also a member of the carrot family and produces a different toxin, cicutoxin. However, unlike poison hemlock, ingestion of this plant causes seizures. A related species, hemlock water dropwort (Oenanthe crocata), is also in the same family and resembles both poison and water hemlock. It contains oenanthotoxin. Both Cicuta and Oenanthe species grow near water—stream banks, lakes, and marshes.
The variety of species within this group of plants includes colorful common names, such as: poison parsley, poison parsnip, cowbane, death of a man, dead man’s fingers, snakeweed, and wild carrot. Those engaging in wild plant foraging sometimes mistake these species for edible carrots or parsnips, but in the case of poison hemlock, the plant has been described as having the odor of mouse urine or a bitter taste, discouraging some seekers.
Was Socrates given the original lethal cocktail—a mixture of conium juice, opium, and other alkaloids? Plato described his symptoms best “The man who administered the poison kept his hand upon Socrates, and after a little while examined his feet and legs; then pinched his foot hard and asked if he felt it. Socrates said no. Then he did the same to his legs; and moving gradually upwards in this way let us see that he was getting cold and numb.”
Fiesseler, F and Shih, R, Poison Hemlock in Critical Care Toxicology, Second Edition, Jeffrey Brent, Senior Editor, Springer, 2017, p. 2205-2211
Cetaruk, E, Water Hemlock in Critical Care Toxicology, Second Edition, Jeffrey Brent, Senior Editor, Springer, 2017, p. 2225-2236