By injecting peroxide of hydrogen into such abscesses before they point through the external tissues, this serious disfigurement can usually be averted, and the suppurative process is materially shortened. It is also a valuable aid for the evacuation of the purulent contents of the antrum of Highmore, in catarrhal and suppurative inflammations, and especially where the sinuses are divided into two or more pockets by bony septi. These cases are often protracted by the inability of the surgeon to perfectly evacuate them. But with this preparation it becomes a simple matter after access has been gained to the cavity by the extraction of a tooth or the perforation of its external wall in the proper place at the juncture of the cheek with the alveolar border. A free opening must always be made for the escape of the contents, in order to avoid pressure from the rapid evolution of gas. Two or three applications of a dram each is usually sufficient to completely empty the sac. It is used with the most gratifying results in the treatment of pyorrhea alveolaris, and is an invaluable agent in treating pulpless teeth, as by its action all decomposed matter from the pulp chamber and dentinal tubuli is readily ejected, thereby removing the most frequent cause of discoloring of this class of teeth, of inflammation of the peridontal membrane, as well as alveolar abscesses. The efficacy of peroxide of hydrogen depends on the case with which it is decomposed into oxygen and water. Pus is one of the many substances which causes this decomposition. Hydrogen peroxide acts first chemically and then mechanically. When the decomposition takes place the oxygen is set free and escapes from a liquid to a gaseous form; this expansion of the gas distends the pus cavity, and as it escapes from the orifice, it carries much of the pus with it, and its application should be repeated till all purulent accumulations are evacuated. The liberated oxygen, being in a nascent or active condition, rapidly oxidizes the products of suppuration, and destroys many of the micro organisms of suppuration.[A] Hence it is a disinfectant and anti-septic. Finally, peroxide of hydrogen, after its decomposition, leaves no material in the system which is foreign to the system, and it is, therefore, one of the most efficient and harmless disinfectants and anti-septics that can be used, in all forms of purulent inflammation.--_Address at American Medical Association._ * * * * *