Gas inhalants

Early gas inhalants included diethyl ether, chloroform, nitrous oxide and carbon dioxide. In 1824 nitrous oxide and carbon dioxide were used during a demonstration of surgery on dogs. It took several decades to be adopted into standard practice but eventually the dental profession embraced nitrous oxide and continues to use it today. 

Although discovered much earlier, diethyl ether, an early inhalant, had its first recorded use in humans in 1842. Chloroform, a much safer alternative followed in 1848. 

Modern inhalant, requiring precision vaporizers for safe administration, were developed much more recently with the most notable ones in veterinary medicine being halothane (1951), isoflurane (approved for medical use in 1979) and sevoflurane (clinical use in 1990).