Destruction by chemical means of the micro-organisms infecting a wound is rendered possible by the different resistances presented by the tissues equipped with a circulation, and the microbes which are found on their surface. The idea must be grasped that a given antiseptic substance, applied at a certain concentration, and during a certain time, is able to destroy microbes without damaging the normal tissues to any appreciable extent. The chemiotherapy of wounds is easier to realise than that of the blood. In the latter case a substance capable of destroying microbes is harmful to the corpuscles, because the resistance of isolated anatomical elements is but little different from that of microorganisms.

The mere application of an energetic antiseptic substance, by any form of technique whatsoever, cannot be relied upon to sterilise a wound. The success of the method which enables us to render aseptic an infected wound is not due to the marvellous properties of a new drug. It should rather be attributed to a combination of means, which enables us to make use of a definite antiseptic substance, under such conditions of concentration and duration that its action becomes efficacious. This method is a combination of which each single part is essential to the rest. The antiseptic cannot be altered without changing the manner of using it. In the same way a modification of the technique demands an antiseptic endowed with different chemical properties.

The technique of sterilisation has been studied, not by a series of experiments in vitro, but actually upon the wounds themselves. While tracing the bacteriological evolution of a wound we have determined the conditions under which a given antiseptic is capable of bringing about rapidly the total disappearance of microbes. By this means we have determined that a substance powerfully bactericidal, yet only slightly irritating, such as Dakin's hypochlorite of soda, will sterilise a wound if it remain in contact with the microbes during a known period of time and at a certain degree of concentration. As the wound responds to treatment in becoming sterile, and as the progress of the sterilisation cannot be gauged by a mere clinical examination, the bacteriological study of the secretions is the guide needed for therapeusis.

The method, therefore, is based upon the employment, rigorously controlled by the microscope, of an approved agent, under conditions of contact, of concentration, and of duration, established by direct experiment upon infected wounds.