Answer: ETHER

AnswerCrossword Clue
ETHERIt can knock you out
ETHERKnockout stuff
ETHERWild blue yonder
ETHERCyberspace metaphor
ETHERFormer anesthetic
ETHEROutmoded anesthetic
ETHERAristotle's "fifth element"
ETHERHeavens
ETHEROld number?
ETHEROne-time surgery aid
ETHERUpper regions
ETHERCompound number?
ETHEROld hospital supply
ETHERIt can put you out
ETHEROld knockout cause
ETHEREarly surgery aid
ETHERNumber no longer used?
ETHEROld knockout agent
ETHEROut-of-use anesthetic
ETHERAnesthetic of yore
ethercolorless liquid used as a solvent and formerly as an anesthetic
ETHERIt's a knockout
ETHEROld-time anaesthetic
ETHEROld-time anesthetic
ETHERSolvent
ETHERAnesthetic
ETHERAnesthetic of old
ETHERCommon solvent
ETHERErstwhile anesthetic
ETHERIt put people to sleep
ETHERIt's a gas
ETHERMedieval atmosphere
ETHEROld anesthetic
ETHERRegion just past the ozone
ETHERIt'll knock you out
ETHERBlue sky
ETHERBygone anesthetic
ETHERSpace, poetically
ETHERUpper atmosphere
ETHEREarly number?