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depressing agencies — alcoholism, insufficient nourishment, loss of blood, etc.; or by a diminished vital resistance at the point of invasion as a result of injury to the tissues by bruising, by burns, by various chemical agents, etc.

When, however, these bacteria have been leading a parasitic life for some time they have a greatly increased virulence, as manifested by their ability to invade the tissues of healthy individuals whenever they find a portal of entrance. Under such circumstances, also, infection may result from the introduction of a very small number of germs, whereas a comparatively large number would be required in case the micrococci had for some time been leading a saprophytic existence.

Fortunately for the human race the blood serum of healthy persons has the power of destroying a limited number of pathogenic bacteria of a low grade of virulence. But when these germs come directly from the seat of an infectious process, especially in the case of the streptococcus, a very small number may give rise to a rapidly extending and deadly blood infection — for example the blood-poisoning resulting from puncture of the skin with a needle during an autopsy of a case of erysipelas or of puerperal fever, or from a surgical operation upon a patient suffering from any form of streptococcus infection. Many pathologists and surgeons have suffered serious and often fatal results from such an apparently insignificant wound.

Antiseptic surgery has for its object the destruction of all bacteria in wounds or attached to objects which are brought into contact with wounds, such as the hands and instruments of the surgeon, surgical dressings, etc. This is accomplished by the use of chemical agents of established germicidal value, which must be used in such a proportion as will insure the destruction of germs, and which will not have an injurious effect upon the vitality of the tissues and the healing process. The principal agents which have been used for this purpose are carbolic acid and corrosive sublimate (mercuric chloride) in solutions of proper strength. There are certain objections to the use of either of these agents in solutions strong enough to promptly destroy disease germs, especially when applied to wounds of considerable magnitude. For this reason antiseptic surgery has to a considerable extent been superseded by aseptic surgery, which accomplishes the same result without the application of chemical agents of any kind to the wound surfaces. Instruments and dressings are rendered sterile by heat, usually in a steam steriliser. The hands of the surgeon and the “field of operation ” are thoroughly scrubbed with soap and water and then washed in an antiseptic solution to insure the destruction of germs attached to the skin. Usually this is followed by washing with alcohol and sterile water to remove all traces of the antiseptic. Many surgeons at the present day prefer to wear india-rubber gloves while operating, as it has been found by experience that it is a difficult matter to thoroughly sterilise the hands. Such gloves are easily cleaned and sterilised. By the “field of operation” is meant the surface of the body in the vicinity of the incisions which are to be made in any surgical operation. This surface is cleaned as thoroughly as possible and other portions of the body are covered with a clean sheet or sterile towels. When the operating-room and its fixtures are “surgically clean ” and all necessary precautions are taken with reference to instruments, dressings, the surgeon's hands, etc., an operation wound is ex. pected to heal promptly by adhesion of the wound surfaces, which have been brought together and retained by sutures or adhesive plaster, and bandages when necessary.

Such wounds treated aseptically rarely suppurate. When they do it is because some of the bacteria which cause pus formation have found their way into the wound in spite of the precautions taken. It is more difficult to prevent suppuration in gunshot wounds and in extensive lacerations resulting from railway accidents, etc. The bruising of the tissues in

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such cases renders them less able to resist infection and less apt to unite by adhesion.

It often happens, also, that the wound is infected at the time it is inflicted. Thus in a gunshot wound a portion of the clothing to which numerous germs are attached may be carried into the wound. Or the bullet itself may be infected, although this is no doubt of rare occurrence.

Lacerated wounds are often inflicted with stones, pieces of wood, or other objects which have dirt adhering to them, which may contain various pathogenic bacteria, and which are liable to remain lodged in the wound. Such a wound may be cleansed and rendered aseptic by being thoroughly washed with sterile water (boiled or distilled), or it may be washed with an antiseptic solution and treated with antiseptic dressings to prevent the development of any bacteria which may chance to remain hidden away in the wound.

CHAPTER XIX

TETANUS

A FORM of wound infection of special interest, be

cause of the very serious results which usually follow such infection, is that by the bacillus of tetanus, which gives rise to the disease commonly known as lockjaw.

The bacillus of tetanus was discovered in 1884, by a student (Nicholaer) in the laboratory of Professor Flügge of Göttingen. Having introduced small quantities of garden earth under the skin of mice and of guinea-pigs, some of these animals died with all the characteristic symptoms of tetanus. Subsequent researches have established the fact that in temperate and tropical regions the bacillus of tetanus is widely distributed and is commonly present in rich soil which has been manured. It is also present in the dust of city streets, and there is good reason to believe that its being found there is due to the fact that it is present in the intestinal contents of horses.

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