The fruit and flowers of Conium maculatum, belonging to Europe and naturalized in the United States. They have an odor resembling that of mice. The active principle is conine, a very volatile alkaloid, freely soluble in alcohol and ether, and slightly so in water. On exposure to the air it decomposes, and this change is assisted by heat.
Conium is a motor depressant, paralyzing the motor nerves from below upward. It affects the respiratory centre, paralyzing it. The cardiac and vascular centres are not specially influenced. The brain is not affected, but remains clear.
When conium is taken in doses just large enough to make an impression, the first effect noticed is muscular weakness in the legs. The feet feel weighted down, or as if made of lead; the knees weak and unable to bear the body, giving an intense desire to lie down, and the patient cannot walk, but staggers and falls.
The eyelids are affected and drop over the eyes; the vision is disordered, and there is frontal headache, with a feeling of heat, as of weight and pressure, in the head.
Conium is also a gastric irritant, producing nausea and vomiting.
It is employed medicinally as a calmative and antispasmodic, but its uncertain, inexact strength is considered to make it unreliable.
In serious poisoning the symptoms mentioned above are all intensified. The pupils dilate; the pulse, at first diminished, afterwards becomes more rapid. The respiratory centre is paralyzed, and death results from asphyxia in a very short time - in one case in a few moments. There are but few recorded cases of fatal poisoning. Hemlock was the State poison of Athens in the time of Socrates, and the means of his death.
No physiological antidote to conium is known. The stomach must be emptied and tannic acid given, stimulants employed and external heat applied, and artificial respiration practised as long as there is any heart action.
Average dose, . iii.-0.2 mil.
Although this is regarded as the best preparation of conium, yet it is very uncertain, because of the volatile character of the essential principle.