In the modern aseptic operating room germicides and antiseptics do not play so important a part as they formerly did. This is largely due to the fact that heat is used wherever possible in the preparation of sutures, ligatures, dressings and instruments, and to the farther fact that in uninfected tissues no antiseptic solutions are employed. It must also be remembered that the germicidal agents possess the disadvantage of exercising a more or less destructive action on the body cells, and consequently their use is not warranted in clean wounds. We still, however, sufficiently often meet with infected wounds that render the use of these agents necessary. +Heat+ is the most valuable of all sterilizing agents, its only drawback being that it is not universally applicable. Wherever possible it should be employed in preference to chemical agents. It can be employed either dry or moist. Moist heat is a much more efficacious germicide than dry heat, for it destroys the organisms at a much lower temperature. Boiling water at a temperature of 212°F. will destroy nearly instantaneously all pus-producing organisms. Spores, however, require a moist heat of 284°F. kept up for at least a half-hour. A dry heat of 212°F. will not destroy pus-producing organisms under an hour and a half of treatment, and spores will live for three hours at a dry temperature of 284°F. Although moist heat is very much quicker and more satisfactory in its action, yet it is often inconvenient to employ it in the sterilization of gowns, towels, operating suits, etc. However, sterilization by heat has been greatly facilitated by the introduction of the autoclave, by means of which a very high temperature under pressure can be obtained. This is the most satisfactory method of sterilizing dressings, towels, sheets, operating suits and aprons. A similar and less expensive method of sterilizing these articles is by the use of one of the simple steam sterilizers which are sold by all dealers. In an emergency, an ordinary bake oven can be employed as a sterilizer. It is best, however, where the temperature cannot be estimated, to boil the articles and dry them between sheets moistened with bichloride solution. +Disinfection or Sterilization.+ Sterilization of a wound, or of the substances coming in contact with it, may be accomplished by using the aseptic or antiseptic method; by combining these two methods we obtain the best results. The aseptic method, which employs antiseptic substances for the purpose of sterilization of objects coming in contact with the wound when their disinfection by heat is impossible, is the method perhaps most generally favored by modern surgeons. +Antiseptic Method.+ In the antiseptic method, the field of operation, the hands of the operator and of his assistants, and the instruments, must be treated in germicidal solution and, in addition, the wound should be frequently irrigated during the operation with a solution that has germicidal properties.