Verrucae are probably contagious, but the pathogenic agent has not been isolated. They sometimes disappear spontaneously, and they will recur if their removal is not complete. +Treatment.+ Certain chemical substances (see “_escharotics_”) destroy tissue and can be employed with safety only after much experience. These drugs when allowed to spread on the normal skin often occasion painful and persistent lesions. They must therefore be applied directly and sparingly to the growth itself and not be left in contact too long. The daily removal of a thin layer is possible in this way without causing pain or erosion. The chemical agents that are employed for the removal of verruca are notably nitric acid, acetic acid, monochloracetic acid, trichloracetic acid, nitrate of silver, sodium hydroxide and salicylic acid. The treatment with these drugs is alike in all cases, with the exception of the last three named. The procedure, when using liquid acids is as follows: render the growth and the surrounding parts aseptic; by means of a tapering glass rod or a wooden toothpick, apply a drop of the acid so that it will spread over the growth only, making certain that every part of the outer surface has been treated. If pain becomes excessive, apply a neutralizing agent. Dress the part with a shield that is holed-out, so that when the foot-covering is in place there will be no pressure over the tissues treated. This treatment should be repeated every other day until there is sloughing at the base of the growth. The pocket produced is drained, and balsam of Peru or some other stimulant should be applied and held in place by an appropriate dressing. Five or six treatments will ordinarily suffice to remove the growth. Many practitioners find nitrate of silver a serviceable remedy in cases of verruca. The pure stick, moistened, is gently applied to the surface of the growth, which later becomes blackened. The patient returns two days later when the scab, that will have formed, is removed and the original treatment is repeated. Ordinarily from six to ten such applications will suffice. Those who favor the use of salicylic acid for the removal of verruca, usually apply a 60 per cent. ointment of this drug, over the growth only, protecting the surrounding parts with collodion or gelatine. A holed-out shield is applied over the growth and an appropriate bandage is made to hold it and the ointment in place. The patient is advised to return at the end of ten days and, as a rule, when the dressing is removed, it will be found that the growth is sufficiently loosened to admit of removal by means of forceps and scissors.