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Updated on July 2, 2010

An antiseptic is a substance which destroys bacteria or keeps them from increasing. The French chemist Louis Pasteur discovered that the tiny forms of life called bacteria are the cause of fermentation and the decay of living matter. In 1864 he was able to show that bacteria are present in the air and can reproduce. Until that time, no one had understood why wounds become infected.

When surgeons performed operations they just washed the knife after cutting into an infected wound and went on using it on other patients. This meant that they were carrying the bacteria, or germs, from one patient to another.

The famous surgeon Joseph Lister (1827-1912), about whom there is also a separate article, had been trying for some time to discover the cause of the gangrene or blood poisoning that often developed after an operation. One of his fellow doctors told him of Pasteur's work and he at once realized that the infection of a wound was a form of decay and must, therefore, be due to the presence of bacteria. If infection was to be prevented these bacteria or germs had to be killed.

At first in 1865 he tried killing them by having carbolic acid sprayed about the operating room during each operation. He also washed his hands, instruments, dressings and the wound with a solution of carbolic acid and water, but the acid proved to be too strong, for it harmed the body. However, Lister's idea of using an antiseptic, or germ-killing substance, was shown to be right because his patients began to recover after their operations and the wounds to heal cleanly. Chemists soon found other antiseptics which were more suitable than carbolic acid and Lister's discovery changed the whole of surgery.

Today, the hands and arms of surgeons and their assistants are thoroughly scrubbed, treated with antiseptic solutions and then covered with sterilized rubber gloves before an operation.

Instruments and dressings are sterilized (that is, they are made free from germs) by heat, chemicals or short-wave radiation. (This kind of radiation, which is given off by radioactive substances, is explained in radiation.) The patient's skin is washed with soap and water, ether or alcohol and either tincture of iodine, hibitane, or some other antiseptic. Ultra-violet sterilizing lamps were introduced in 1942 to sterilize the air in many operating theaters, but nowadays sterilizing the atmosphere in the operating theater is less common than air conditioning or filtration.

In addition to these manufactured antiseptics the body itself has certain ways in which it defends itself against bacteria and germs. Tears, sweat, saliva in the mouth, fluids in the tissues and blood contain substances which resist common infections. The greatest of nature's antiseptics are the white cells (or corpuscles) in the blood. These have the important quality of being able to consume harmful bacteria that enter the blood stream or infect a part of the body. When such bacteria are present in the body, the white corpuscles of the blood devour the invaders. They are usually strong enough to destroy the bacteria unless the latter increase in number too quickly. The pus in an infected wound or sore is really only a fluid which consists of liquefied body cells, living and dead bacteria and white cells, and liquid from the blood.

In the same way that bacteria attack human beings and cause infection, so they also attack meat and vegetables and other food, making them go bad. If food is to be kept for any length of time the bacteria must not be allowed to grow. The food has to be sterilized or kept germ-free just as wounds have to be sterilized. Bacteria only grow under favorable conditions; these include moisture, a fairly warm atmosphere and food. Some bacteria need air in which to grow but others do not. Thus meat which has to be kept for a long time is frozen; this makes it too cold for the bacteria to grow until it is thawed out again. Tinned vegetables and other foods will keep for a long time because the tinning process affects the food in a way which prevents the harmful bacteria from growing. Water is free from germs when it has just been boiled, as again the heat has killed all the bacteria. That is why you are always told to wash cuts in water that has been boiled and also why you have to boil water to drink when you are out camping or picnicking far from properly purified tap water.

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