M. Lumiere's experiments prove, therefore, that hypochlorite of soda destroys toxins contained in pus. This destruction of toxins by oxidising antiseptics plays a favourable part in sterilisation, either in allowing phagocytosis to become effectual, or in preventing the impregnation of the organism by noxious substances. Perhaps it explains, in part at least, the rapid disappearance of general symptoms, presented by patients suffering from extensive suppuration, when their wounds are treated by Dakin's solution.

3. Toxicity of Dakin's Solution. - Hypochlorite of soda is very slightly toxic to the organism, when it is injected on the surface of wounds, or, in animals, into the subcutaneous cellular tissue. We have injected under the skin of the abdominal wall of guinea-pigs quantities of antiseptic relatively considerable, without unfavourable result. For example, three guinea-pigs weighed respectively 565 grammes, 570 grammes, and 510 grammes. These had respectively 8 c.c, 11.4 c.c, and 1275 c.c. of Dakin's solution, that is to say, 1/70, 1/50, and 1/40 of their body-weight. They presented no abnormal symptom, and remained in good health.

Hypochlorite of soda, which is harmless when sub-cutaneously injected, is very dangerous if injected into the general circulation. An injection of ten cubic centimetres into the marginal vein of the ear of a large rabbit rapidly caused death. Hypochlorite of soda is strongly haemolytic, and therefore should never be injected into veins. Indeed, it is prudent never to inject it under pressure into deep wounds, in order that it may not be absorbed by the tissues. Amongst the numerous cases of wounded men treated by hypochlorite of soda, we have never had accidents which could be attributed to a toxic action of this substance.

4. Action of Hypochlorite on the Tissues. - Experiments made upon guinea-pigs had already shown that a small quantity of hypochlorite of soda injected into a fragment of sponge placed under the skin, produced no modification of the tissues obvious to clinical examination. Further, Dakin's solution, instilled for several days, sometimes several weeks, over the surface of a wound, in a general way set up no marked irritation. It was already evident from these observations that Dakin's hypochlorite had little action upon the tissues. However, more exact experiments were initiated, in order the better to determine the action of the antiseptic on dead tissues, on isolated anatomical elements, and on tissues deprived of circulation.

{a) Action of Hypochlorite on Tissues deprived of Circulation. - When fragments of skin from a guinea-pig or a human foetus are placed in Dakin's solution, the tissues begin to disintegrate at the end of twenty-four hours. The same is true of fragments of mortified tissues. This action is less marked if electrolytic hypochlorite be employed. On the surfaces of wounds mortified tissue dissolves, as a rule, in five or six days; but occasionally fragments of tendons or aponeuroses are left adhering to the tissues, and persist for a longer period. Dakin's solution appears incapable of sterilising a fragment of necrosed tissue on the surface of a wound. In such a fragment bacteria would find a safe refuge. In the treatment of wounds, therefore, it is indispensable to employ a substance capable of dissolving tissues deprived of circulation. On the other hand, if the wall of a blood-vessel is mortified, the slough falls off more rapidly than if the wound is left to itself. Similarly, the clots which often obliterate vascular wounds are enabled to dissolve under the action of hypochlorite. For this reason we must carefully examine the condition of the vessels at the moment of surgical intervention, and must effect an accurate preventive haemostasis.

(b) Action of Hypochlorite on Isolated Anatomical Elements. - If blood or pus is placed in a tube containing an excess of hypochlorite, the red corpuscles are rapidly attacked. When the volume of hypochlorite is sufficient the anatomical elements are completely disintegrated. However, in the secretions of wounds treated by hypochlorite the polynuclear cells are not much altered, and often contain microbes. It is probable that phagocytosis occurs in the walls of the wound, out of reach of the antiseptic substance, which remains on the surface of the tissues. Generally speaking, there is no need to accomplish the dissolution of those leucocytes which have absorbed micro-organisms; but in certain cases the complete destruction of the phagocytes is of importance. This conception is unknown to the French surgeons, who generally speaking confuse the chemiotherapy of local infections with that of general infections.

In the chemiotherapy of general infections the antiseptic substance should be injected into the circulatory system; it must not, accordingly, exert an injurious action upon the leucocytes. If, indeed, it were to prevent phagocytosis it would deprive the organism of one of its most valuable means of defence.

In the chemiotherapy of local infections the importance of the leucocytes is of a totally different nature. Indeed, as the bactericidal substance does not sink into the depth of the tissues, its action is exerted only on the surface of the wound. The leucocytes existing in the wall of the wound are able to continue their functions, even if the bactericidal substance is injurious to them. As for the leucocytes which occur on the surface of the tissues, they are replaced by a chemical substance whose bactericidal action is much more powerful than their own. On the other hand, large numbers of these leucocytes, having phagocytosed the microbes, are still living, and may once again enter into the tissues and there spread the infection. The researches of Rous1 have demonstrated that the red corpuscles or the pathogenic phagocytosed microbes are protected by the wall of the leucocytes from the humours of the organism and from bactericidal chemical substances. It is thus important to destroy, on the surface of wounds, the leucocytes which are loaded with bacteria, as well as the pus bacteria. The so-called cytophylactic medication of a local infection is based on ignorance of the protective role which the leucocytes fulfil in respect of the microbes. It may produce disastrous results, above all in cases of cerebral wounds. Indeed, we find in the secretions of such wounds leucocytes which are loaded with microbes, which remain included in the cerebral substance at the moment of cicatrisation. It is probable that the protection offered to the microbes by the phagocytes which have absorbed them enables them to produce secondary retractile cicatrices, or encephalitis, or a cerebral abscess.