Chloroform
It was David Waldie that first suggested utilizing chloroform fumes for practical purposes. However, it was James Simpson that was the first to try chloroform and recognize its usefullness. Simpson and his friends tested chloroform and passed out in the laboratory. Simpson was the first to regain conciousness. It was at that moment Simpson realized the power of chloroform. Chloroform was used as a general anaesthetic in Great Britain for the next 50 years, up until the early 1900s. Perhaps the most important surgery in chloroform's history was its use as anaesthesia on Queen Victoria. Although chloroform was a very powerful anaesthetic its use was dicontinued because it was too dangerous and is very toxic to the human body.
Simpson invented a mask so that the patient was able to breathe chloroform from the operating table. The surgeon simply held the mask, saturated in chloroform, over the patient's face until the patient was unconcious. Surgery was conducted only after several minutes of preparation.