of roots had no effect in the month of April; but that two pounds in the end of May, when the plant was in full vegetation, killed a dog in six hours.[1] The alcoholic extract of the juice obtained from six ounces of roots on the last day of May, I have found to kill a rabbit in thirty-seven minutes, when introduced in a state of emulsion between the skin and muscles of the back; and the effects were analogous to those obtained with the extract of the leaves. The differences depending on season will probably account for various persons having found the juice of the root harmless. Gmelin quotes an instance where four ounces of the juice were taken without injury. He adds another where three ounces of the juice of the herb were swallowed daily for eight days with as little effect. But, as he judiciously observes, other less active plants have probably been sometimes mistaken for hemlock.[2]
The alkaloid, conia, seems to be the active principle of hemlock, and is a poison of extraordinary virulence. On investigating this subject in 1835,[3] I found that it is a local irritant, possessing an acrid taste, and capable of exciting redness or vascularity in any membrane to which it is applied; but that these topical effects are readily overwhelmed by its swift and intense narcotic action. This action consists of swiftly spreading palsy of the muscles, which affects first those of voluntary motion, then the respiratory muscles of the chest and abdomen, and lastly the diaphragm, so as to terminate by causing asphyxia. The paralytic state is usually interrupted from time to time by slight convulsive twitches of the limbs and trunk at the beginning. The muscular contractility is impaired or annihilated by the topical action of the poison, but not by its indirect action through absorption. The heart is not appreciably affected; for it contracts vigorously long after all motion, respiration, and other signs of life are extinct; and it contains after death, not florid but dark blood in its left cavities. The blood undergoes no alteration. The external senses are little, if at all impaired, until the breathing is almost arrested; and volition too is retained. But a contrary inference may be drawn by a careless observer, in consequence of the paralytic state taking away the means, by which in animals sensation is expressed and volition exercised. The action of conia, in short, is confined to the spinal cord; and it acts as a sedative, by exhausting the nervous energy.
Conia is probably a deadly poison to all orders of animals: at least I found it to be so to the dog, cat, rabbit, mouse, frog, fly, and flea; and Geiger killed the kite, pigeon, sparrow, slow-worm, and earth-worm with it. It acts through every texture where absorption is carried on readily, through the stomach, eye, lungs, cellular tissue, peritonæum, or veins; and its activity is in proportion to the speed with which absorption is carried on in the part. It acts therefore through absorption. Its activity is increased by neutralization with an acid, by which it is rendered much more soluble in water. Few
