This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
Lunar caustic has proved useful sometimes in aborting purulent formations. The absence of pitting after small-pox being dependent upon the small size and limited inflammation of the pustules, Velpeau and others have endeavored to secure such a result by puncturing the vesicle on the third or fourth day, and touching the interior with a fine point of the nitrate; and if well carried out this plan has often succeeded. It is painful, tedious, and not free from danger, but the plan devised by Dr. F. Bowen is an improvement upon it, and is much more feasible: the vesicle is to be punctured with a fine needle dipped in a solution of the salt (20 gr. to 1 oz.); a nurse can do this quite well. In one case all the parts thus treated recovered perfectly, while the vesicles that were untouched left deep scars (quoted by Ringer). Mr. Higginbottom recommends painting of the face with the same strong solution that he used for erysipelas (80 gr. to 1/2 oz.), but this is too painful for ordinary use.