DZ is fond of browsing in old bookshops. In particular he likes medical textbooks from the 1920s and 30s, and autobiographies of doctors who worked at the time. It's fascinating to read about some of the things we used to do to people.
For example. I found an old textbook of anaesthesia, in which was described the "nitrous oxide jactitation technique" of starting anaesthesia.
Apparently what you did was this. You put a mask on the patient's face and administered 100% nitrous oxide. That is, no oxygen. None at all. Unsurprisingly, in a very short time the patient became blue, and unconscious. The anaesthetist (who at that time was likely to be the surgeon's houseman) continued to administer 100% nitrous oxide until the patient exhibited a phenomenon known at the time as "jactitation". What is known today as a hypoxic fit! The houseman would only then switch in oxygen, and ether, and all was well. Apparently.
It sort of puts in perspective the panic you see in today's anaesthetists when the saturation drops below 90%.
I've mentioned this technique to a number of anaesthetists and only one (older generation) had ever heard of it. He assures me that the technique was still used, mainly by dentists, right into the 1960s.
something of a comeback. You'd think wouldn't you that if people were going to sell N2O for recreational purposes that it might be a good idea to put some O2 in. Just 20% would do