It acts especially on the superficial sensory nerves, and tends to extinguish feeling and pain. It is the best external anæsthetic with which we are acquainted. It is thus eminently useful in the treatment of that most painful of all disorders, Tic douloureux, or irritative Neuralgia of the face. When Quinine and all internal remedies have failed, the tincture of Aconite, or an ointment containing the alkaloid, will in most cases, if applied to the part, effectually relieve the pain. It is applicable in local irritative pain at any part of the surface, as in Sciatica, Lumbago, or a Scirrhus of the breast that has not opened. But, like the other local anæsthetics, it is of little service in cases of inflammatory pain, for this, when local, depends upon an active cause, and would be liable to be increased by the rubbing required in the application of the Aconite. When the remedy takes effect, some heat is first experienced at the part; there is then tingling; and lastly, complete numbness, and a sensation of cold, which endure for some time. No visible change is effected. Aconite subdues the action of the heart. Dr. Fleming has therefore recommended small doses internally in cases of acute rheumatism. But considerable care is required in the internal employment of the drug, on account not only of its dangerous properties, but of the great variety in strength which exists among the preparations that are usually employed. The difficulty experienced in the preparation of the alkaloid Aconitina, which is the active principle of the plant, and the very high price at which that substance is usually sold, have prevented it from being so extensively employed in practice as its medicinal properties would appear to deserve for it. On account of its cleanliness as an outward application, and the certainty and uniformity of its sedative and anæsthetic actions, the pure alkaloid is far preferable as a medicine to Aconite itself, and is adapted for all the cases in which the latter has been employed. Having some time ago been successful in an attempt to discover a mode of preparing Aconitina,[49] I have made some experiments with it on various small animals, for the purpose of ascertaining its power, and the symptoms of its action. It is a very active poison. Proceeding upwards in the animal scale, I find that 1/300th of a grain, in solution in water, suffices to kill a mouse. 1/100th kills a small bird after a few minutes; 1/50th almost instantaneously. 1/20th of a grain has killed a cat. 1/10th invariably proves fatal to the unfortunate feline in the course of twenty minutes or half an hour. Calculating as well as I can from these data, I consider that 1/10th of a grain of this alkaloid would be sufficient to cause the death of an adult man. During the action of the poison on cats the following succession of symptoms is generally observed. They will illustrate in most of its phases the action of a Sedative medicine.