Related Clues:

• It's a gas?
• Inhalation anesthetic of old
• It's a gas!
• Preoperative delivery of old
• It'll knock you out
• Once-popular anesthetic
• Old number?
• Old-time anesthetic
• It could knock you out
• Bygone anesthetic
• Upper region of space
• It puts people out
• Obsolete anesthetic
• Anesthetic gas
• Procaine predecessor