In the film “Sherlock Holmes and the Game of Shadows,” Holmes identifies the poison on a dart that had instantly paralyzed a victim by sniffing it. “Curare!” he says. Curare is a very real poison but identifying it by smell is pure fiction. In the form of an extract made from the root or stem of a certain species of climbing vine, known today as Chondodendron tomentosum, it was used by native South Americans to tip their arrows long before the Europeans arrived. There were stories about how the lethal brews were secretly mixed. Tales were told about the oldest women in the tribe who would prepare the mixture in closed huts, and if after two days, the fumes had not killed them, the mixture would be judged too weak to use and another batch would be begun. That’s fiction too. The toxin is not volatile.
It was Sir Walter Raleigh who took a sample back to Europe, where it was given the name "curare" derived from the Indian word for poison. Unfortunately, not much attention was paid to the substance until 1812 when Charles Waterton realized that if the right dose were used, muscle relaxation without death could be achieved. Curare came to be used in the treatment of lockjaw, infantile paralysis and even epilepsy.
It wasn't until 1844 that the mechanism of action of curare began to be understood. The French physiologist Claude Bernard experimented with frogs and found that curare blocked nerve impulses from the brain to the muscles and had the effect of relaxing the muscles to the point of limpness. Even the muscles which controlled breathing could be made to relax to the point that the animal appeared to be dead. If the dose was just right, the effect would soon wear off and recovery was complete. One might say that the animal had experienced a living death.
When, the active ingredient in the climbing vine was finally isolated and identified as tubocuranine, modern medicine began to find a use for it. It was found to counter the effects of some muscle-contracting poisons such as strychnine and tetanus toxin, and even more importantly, it found use as a muscle relaxant during surgery. Curare greatly facilitated abdominal surgery by preventing the muscles from becoming stiff and almost unpenetrable. It was first used in 1942 during an appendectomy at Montreal’s Homeopathic Hospital (later the Queen Elizabeth Hospital) by Dr. Harold Griffith who served as Chairman of McGill University's Department of Anesthesia.
Dr. Griffith spent his life researching anesthesia and was probably more responsible than anyone else in establishing the field as a medical specialty. He received numerous awards for his work but his contributions are probably best encapsulated in one of his biographer’s telling comments: “There are only two eras in anesthesia,” he wrote, “before Harold Griffith and after.”
Curare itself is now rarely used because it has been supplanted by more effective synthetic derivatives. These, such as pancuronium, better known as Pavulon, are more potent and can be used in smaller doses. Side effects are more limited. Now, back to the movie. It isn’t actually based on any of the real Sherlock Holmes stories, but various bits from Conan Doyle’s classic tales find their way into the film. Curare is one of these. It plays a vital role in the Sussex Vampire, one of the 56 short stories. It is no surprise that Conan Doyle incorporated poisons into several of the Sherlock sagas because he was a medical doctor. But it seems he didn’t have any practical experience with curare,or he would have noted that it has no smell.