Curare is a poison, that was used as an arrow poison by Native South Americans. Actually, curare is any of a number of such substances, all similar. The main active substance of curare is tubocurarine. It is an alkaloid that can be extracted from several plants, including Chondodendron Tomentosum . The poison produces muscle paralysis by interfering with neuro-muscular junctions. It inhibits reception at the receptor sites of skeletal muscles. Highly innervated muscles are affected first.

In recent years curare has been put to medical use. Anaesthesia-induced complications are reduced when curare is added to the anaesthetic, as a smaller amount of anaesthesia is necessary for inducing the necessary muscle relaxation.

Modern advancements in medicine allowed scientists to discover curare's physiological effects. Before, though, all science knew was that in large amounts curare could kill, and in small amounts inhibit (apparently), nervous trasmission. This basically means that doctors could see that when a small amount of curare was given to a patient, he acted exactly as if under anaesthesia, or in a coma. His body becomes relaxed and he does not respond to pain. Now, when a person is anaesthesised, all of his nervous system is affected (sensory neurons and motor neurons). So he can neither feel nor move. Curare, on the other hand, does not affect the sensory nervous system. So unlike with anaesthesia, the person can feel everything, but his muscles cannot move.

From the doctor's side, however, there is no way to tell the difference just by looking, and there was no reason to assume curare acts this way. So operations were performed using curare as the anaesthetic. The patients felt EVERYTHING, but could do nothing. Doctors did not believe the patients' complaints at first, but when they saw that there were many such reports, they began to believe them, and stopped using curare alone in surgery.