Medical doctors and dentists can perform all kinds of operations without causing pain. This is thanks to the discovery of chemicals and gases that take away the patient's power of feeling.
All anesthetics work by preventing the action of the nerves that carry pain signals. There are four different kinds.

   Surface anesthetics, such as lignocaine gel, may be rubbed onto the skin or mouth lining. Or, like ethyl chloride, they may be sprayed onto the skin. They take away feeling only for a very short time. They affect the endings of the nerves by freezing the skin or mouth lining. The surface anesthetic can be used to make injections painless.

   Local anesthetics are injected through a needle, which passes through the skin. The chemical, such as procaine or lignocaine, spreads out near the place that the needle entered. Only the nerves in this region are stopped from working. This local anesthesia begins a few minutes after the injection and lasts for an hour or more. It enables a surgeon to perform small operations.

   Another kind of anesthesia is spinal anes­thesia. This time the injection is given in the middle of the back. The chemical catches the larger spinal nerves where they join the spinal cord.

   Spinal anesthesia takes away all feeling of pain in the lower parts of the body. It can be used in operations on the lower parts of the body. It may also be used when a woman is giving birth to a child.

   In general anesthesia the brain, and therefore the patient, is put to sleep while the operation is being performed. The sleep is deep enough to stop any pain. Major hospital operations usually require a general anesthetic.
   As long as the patient breathes the gas, he stays asleep and feels no pain. The gases used in general anesthesia stop the thought and action parts of the brain from working properly. They are called the higher centres, and they are effectively asleep. The parts of the brain that keep the patient breathing and the blood circulating are called the vital centres. They go on working.

   The medical doctor who gives the anesthetic is called the anesthetist, or anesthesiologist. He first makes the patient sleep by giving him an injection in a vein in the arm. He then places a mask on the patient's face and passes anesthetic gas through a tube into the mask.

   General anesthesia may be needed for only a short operation. The anesthetist can then give a simple injection into the arm vein. A drug like Pentothal can be given in this way so that the patient goes to sleep in a few seconds. The anesthetic lasts for five to ten minutes, after which the patient wakes up quickly. Broken bones can be put back in the right position without pain when Pentothal is given.