The veterinary surgeon, when operating on the horse, or cattle, or the dog, frequently has recourse to the actual cautery. I could, perhaps, excuse this practice, although I would not adopt it, in superficial wounds; but I do not know the instrument that could be safely used in deeper ones. If it were sufficiently small to adapt itself to the tortuous course of little wounds, it would be cooled and inert before it could have destroyed the lower portions of them. If it were of sufficient substance long to retain the heat, it would make a large and fearful chasm, and probably interfere with the future usefulness of the animal. The result of the cases in which the cautery has been used proves that in too many instances it is an inefficient protection. The rabid dog in Park Lane has already been mentioned. He bit several horses before he could be destroyed. Caustic was applied to one of them, and the hot iron to the others. The first was saved, almost all the others were lost. A similar case occurred last spring; the caustic was an efficacious preventive; the cautery was perfectly useless. What caustic then should be applied? Certainly not that to which the surgeon usually has recourse--a liquid one. Certainly not one that speedily deliquesces; for they are both unmanageable, and, what is a more important consideration, they may hold in solution, and not decompose the poison, and thus inoculate the whole of the wound. The application which promises to be successful, is that of the 'lunar caustic'. It is perfectly manageable, and, being sharpened to a point, may be applied with certainty to every recess and sinuosity of the wound. Potash and nitric acid form a caustic which will destroy the substances with which they come in contact, but the combination of this caustic and the animal fibre will be a soft or semi-fluid mass. In this the virus is suspended, and with this it lies or may be precipitated upon the living fibre beneath. Then there is danger of re-inoculation; and it would seem that this fatal process is often accomplished. The eschar formed by the lunar caustic is dry, hard, and insoluble. If the whole of the wound has been fairly exposed to its action, an insoluble compound of animal fibre and the metallic salt is produced, in which the virus is wrapped up, and from which it cannot be separated. In a short time the dead matter sloughs away, and the virus is thrown off with it. Previous to applying the caustic it will sometimes be necessary to enlarge the wound, in order that every part may be fairly got at; and the eschar having sloughed off, it will always be prudent to apply the caustic a second time, but more slightly, in order to destroy any part that may not have received the full influence of the first operation, or that, by possibility, might have been inoculated during the operation. Mr. Smerdon, in the Medical and Physical Journal, March 1820, thus reasons: