The actual cautery has many useful applications in dermatology. In employing it, however, the importance of maintaining and using a temperature appropriate to the operation in hand must not be overlooked. With the older iron cauterizers this was difficult, as the metal began to cool the moment it was withdrawn from the fire, and hence if the operator desired to employ the heat at a particular temperature he was often obliged to manipulate with a degree of rapidity that was inconsistent with proper care. This is especially true of small instruments which rapidly lose their heat.

The effects produced by different degrees of heat vary greatly. If a white heat is employed the pain is not so great, the slough is smaller, the ulcer heals quickly and with very little reaction, and the scar possesses far less of the retractile character which is displayed by cicatrices resulting from burns at a comparatively low temperature, as those from burning clothes or boiling water, the scars from which so often produce serious deformity, a fact which must always be borne in mind in cautery operations. In certain operations a white heat is not desired, as a dull heat will better fulfil the special indications. We should therefore well consider the temperature best suited to the particular case, and should possess the means of maintaining and controlling it. The difficulty of accomplishing this, with the blow-pipe or furnace as the source of heat, greatly limits the use of the ordinary cautery irons.

Twenty years ago, Middeldorff brought into prominent notice another method of generating heat for surgical purposes, namely, by the aid of electricity. By this means he obtained perfect control of the temperature, but the apparatus was expensive and cumbrous. The consequence was that galvano-cautery was rarely used, except imperatively demanded, and many useful applications of the method were neglected or replaced by less efficient means of treatment.

During the past few years, however, the prominent objections to the employment of the galvano-cautery have been dissipated by the invention of several exceedingly efficient and convenient batteries of American construction.* The one shown below (Fig. 2) is adapted to major as well as minor operations. It weighs 12 lbs. and its dimensions are 6 1/2 x 9 x 10 inches. It is capable of heating twenty inches of No. 22 platinum wire, and keeps up a working heat for from thirty to forty minutes.

For very many purposes the galvano-cautery is inferior in convenience to the "thermo-cautery" invented by Pa-quelin of Paris. With it, as with the galvano-cautery, any desired degree of heat can be obtained and maintained for a long time, at the will of the operator, or varied from moment to moment as may be necessary.

Besides these the burning-glass, or solar cautery, deserves mention, as it is within the reach of all, and when skilfully handled is capable of being made exceedingly useful. A lens of four inches diameter and six inches focus will answer perfectly for the destruction of small growths, naevi, etc. The lens should be fitted with a handle and should not be employed in an operation until the surgeon has acquired some skill in adjusting the focus, etc., by practice on some inanimate object, as for example, a piece of board. The effort, of course, is to instantly focus the heat on the exact spot that we wish to destroy, without parbroiling an indefinite area of surrounding skin. In using the solar cautery the glare of light is so intense at the focus that it prevents a distinct view of the point to which the application is made. This may be remedied by wearing blue-glass spectacles.

Fig. 2. - The author's galvano-cautery.

Fig. 3. - Paquelin's thermo-catitery.

* These instruments are in every way superior to anything of the sort manufactured abroad. They arc likewise much cheaper than the less efficient instruments of a few years ago.

The principal diseases in which the actual cautery may sometimes be used to advantage in dermatological practice are angioma, naevus, rosacea, varicose veins, lupus, epithelioma, ulcers, chancroids,* venereal warts, and pedunculated tumors of the skin. We have employed it in all of these affections, and find that it often accomplishes results not so easily or conveniently attainable in other ways. The value of the actual cautery was appreciated by Hippocrates who is credited with the following: "Quoe medicamenta non sanant, ea ferrum sanat. Quoe ferrum non sanat, ea ignis sanat. Quoe vero ignis non sanat, ea insanalilia reputare oportet"

* Archives of Clinical Surgery, November, 1876.