§ 598. Tests.—Picric acid is easily separated from either tissues or other organic matters. These are acidified with sulphuric acid and then treated with 95 per cent. alcohol; the alcohol is filtered off, distilled, and the residue treated with ether; this last ethereal extract will contain any picric acid that may be present.
If the ether extract contains much impurity, it may be necessary to drive off the ether, and to take up the residue with a little warm water, then to cool, filter through a moistened filter paper, and test the aqueous solution. Picric acid, warmed with KCN and KHO gives a blood-red colour, from the production of iso-purpurate of potash. Ammoniacal copper sulphate forms with picric acid yellow-green crystals which strongly refract the light. If a solution of picric acid be reduced by the addition of a hydrochloric acid solution of stannous chloride, the subsequent addition of ferric chloride produces a blue colour, due to the formation of amidoimidophenol hydrochloride C6H2OH(NH2)(NH)2HCl.
V.—Cicutoxin.
§ 599. The Cicuta virosa, a not very common umbelliferous plant growing in moist places, is extremely poisonous. It is from 3 to 4 feet in height, with white flowers; the umbels are large, the leaves are tripartite, the leaflets linear lanceolate acute, serrate decurrent; the calyx has five leaf-like teeth, the petals are obcordate with an inflex point; the carpels have five equal broad flattened ridges with solitary stripes. Böhm[616] succeeded, in 1876, in separating an active principle from this plant. The root was dried, powdered, and exhausted with ether; on evaporation of the ether the extract was taken up with alcohol, and after several days standing the filtrate was treated with petroleum ether; after removing the petroleum, the solution was evaporated to dryness in a vacuum; it was found to be a resinous mass, to which was given the name cicutoxin. It was fully soluble in alcohol, ether, or chloroform, and was very poisonous, but what its exact chemical nature may be is still unknown.
[616] Arch. f. exp. Path., Bd. v., 1876.
§ 600. Effects on Animals.—Subcutaneously injected into frogs, cicutoxin acts something like picrotoxin, and something like the barium compounds. Ten to fifteen minutes after the injection the animal assumes a peculiar posture, holding the legs so that the thigh is stretched out far from the trunk, and the leg at right angles with the thigh; voluntary motion is only induced by the strongest stimuli, and when the frog springs, he falls down plump with stiffly stretched-out limbs. The frequency of breathing is increased, the muscles of the abdomen are thrown into contraction, and the lungs being full of air, on mechanical irritation there is a peculiar loud cry, depending upon the air being forced under the conditions detailed through the narrow glottis. Tetanic convulsions follow, gradually paresis of the extremities appears, and, lastly, full paralysis and death; these symptoms are seen after doses of from 1 to 2 mgrms. The lethal dose for cats is about 1 centigrm. per kilo. Diarrhœa, salivation, and frequent breathing are first seen, and are followed by tonic and clonic convulsions, then there is an interval, during which there is heightened excitability of reflex action, so that noises will excite convulsions. Small doses by exciting the vagus slow the pulse; larger doses quicken the pulse, and raise the arterial pressure. Cicutoxin is supposed to act specially on the medulla oblongata, while the spinal cord and the brain are only secondarily affected.