In the 16th century, a Swiss - born physician commonly known as Paracelsus made chickens breathe sweet vitriol and noted that they not only fell asleep but also felt no pain.
स्पेनी डॉक्टर रेमन्ड लुलुस ने रसायनों का परीक्षण करते वक्‍त एक ऐसा तरल पदार्थ बनाया जो वाष्पशील और ज्वलनशील था ।