Inhalational anesthetic

[3] The ideal volatile anaesthetic agent offers smooth and reliable induction and maintenance of general anaesthesia with minimal effects on non-target organ systems.

[4] Other gases or vapors which produce general anaesthesia by inhalation include nitrous oxide, carbon dioxide, cyclopropane, and xenon.

Nitrous oxide, even at 80% concentration, does not quite produce surgical level anaesthesia in most people at standard atmospheric pressure, so it must be used as an adjunct anaesthetic, along with other agents.

[11] Prior to the development of modern anesthetics, CO2 was used extensively by psychiatrists in a treatment called carbon dioxide inhalation therapy.

"Anesthetics have been used for 160 years, and how they work is one of the great mysteries of neuroscience," says anaesthesiologist James Sonner of the University of California, San Francisco.

Anaesthesia research "has been for a long time a science of untestable hypotheses," notes Neil L. Harrison of Cornell University.

Helium at high pressures produces nervous irritation ("anti-anaesthesia"), suggesting that the anaesthetic mechanism(s) may be operated in reverse by this gas (i.e., nerve membrane compression).

[14] He used sweet oil of vitriol (prepared by Valerius Cordus and named Aether by Frobenius):[14] used to feed fowl: “it was taken even by chickens and they fall asleep from it for a while but awaken later without harm”.

[14] Subsequently, about 40 years later, in 1581, Giambattista Delia Porta demonstrated the use of ether on humans although it was not employed for any type of surgical anesthesia.

[15] After the experiments and publications by the Scottish obstetrician James Young Simpson in late 1847, chloroform became the first widespread halocarbon anaesthetic.