Aconite is a powerful anæsthetic to the superficial sensory nerves. When applied in solution or ointment to the surface of the skin, it produces first some heat and tingling, which is attributable to a derangement of the nervous influence; and this is succeeded by perfect numbness. It is thus a most valuable topical remedy in true irritative Neuralgia. Other Sedatives and Narcotics have the same power as topical anodynes, but not in so marked a degree. In large doses Aconite is a General Sedative; producing tingling of the extremities, vomiting, and syncope; and affecting the brain in various ways, as will be shown by some experiments which I have made upon its action, to be detailed in the fourth chapter. An alkaloid called Aconitina, the most powerful of all known medicines, is the active principle of this drug. Conium (Hemlock) also owes its properties to the alkaloid Conia. Dr. Christison has made some experiments upon the latter. He found that it produced swiftly-spreading paralysis of the motor nerves; and he considers it to act particularly as a Sedative to the reflex spinal functions. It also paralyzes the sensory nerves, but in a less degree. Conium is certainly anodyne; and produces often a sedative action on the heart. It would thus appear to be a General Sedative. But in some recorded cases of poisoning by Hemlock, coma has been mentioned as a leading symptom. Were this to be authenticated, and shown to be the invariable result of the action of this medicine in large doses, then it ought certainly to be classed among Narcotics. Dr. Pereira considers it likely that the plant contains more than one active principle. Hemlock has a paralyzing action on the nerves of motion, which is directly the reverse of the stimulating action of Strychnia; and is thus of use in cases of convulsion and spasm. It is also often prescribed as an anodyne. Conium is further said to have a curious resolvent power over glandular enlargements, and to have thus frequently caused their absorption and disappearance. This action was first noticed and described by Dr. Fothergill. All true resolvents operate by an action in the blood, but it is difficult to conceive how such an action can be exerted by a nerve-medicine. It may possibly act indirectly by quieting the action of the heart, and controlling an irritable state of the nervous system. In the same way Opium often appears to act as a resolvent. And it is certain that Hemlock, when used for this purpose, very often fails altogether. It has been wrongfully extolled as a panacea in Phthisis; but is in fact of no greater use in that disorder than Hyoscyamus, Prussic acid, and other medicines which reduce the pulse. For the patient in this disease is devoured by a continual slow fever, and any thing which tends to lower this fever will serve to prolong his existence. But altogether it must be admitted that considerable mystery attaches to the operation of this medicine.