Caustics are used to destroy excrescences on the surface of the skin and mucous membranes : warts, condylomata, or polypi; to destroy exuberant and unhealthy granulations in ulcers and fungating sores: thus, a slight touch with nitrate of silver, sulphate of copper, or with nitric acid, will sometimes cause the tissues in an unhealthy wound after an operation to become less exuberant, and take on a healthy healing action.

Caustics may be used to destroy malignant growths. Generally a surgical operation is preferable for this purpose, but sometimes patients have such a horror of the knife that they will not submit to an operation, and in such cases caustics are occasionally employed. For this purpose one of the following may be applied: Vienna paste consisting of caustic potash and caustic lime moistened with water, or London paste, which consists of caustic soda and lime moistened with alcohol. Sulphuric acid mixed with sawdust has sometimes also been used, but it is exceedingly painful. Arsenious acid made with various inert substances into a paste is not unfrequently employed with considerable success by charlatans, who sometimes succeed in removing cancerous growths by its application in apparently hopeless cases, but the risk attending its use is considerable.

Caustics are sometimes employed also to open abscesses, especially abscesses of the liver, if it is thought advisable to cause adhesions between the viscus and the abdominal wall before the abscess is opened, so as to avoid any risk of pus finding its way into the abdominal cavity. The substance usually employed for this purpose is caustic potash.

Caustics are also used to keep up chronic irritation, as in chronic headache or epilepsy, a wound being first made by the use of the caustic, and prevented from healing by the introduction of a foreign body into it, or by the continued application of some irritating ointment, such as savine ointment.

Caustics are also used as an application to the bites of venomous serpents, or of rabid dogs, in order to destroy the virus and prevent its general action on the organism. The weaker caustics are of no use for this purpose. I have seen a boy die of hydrophobia six weeks after he was bitten by a mad dog, although the wound had been thoroughly cauterised by nitrate of silver five minutes after the bite. In all cases the parts around the bite should be, if possible, excised and then cauterised with a red-hot iron, a ligature being, if possible, placed between the bitten part and the heart until the operation has been effected, so as to prevent any absorption of the virus.