The Doctor's gas (The Arkwood Experiments)
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When faced with an angry herd of volcano creatures, the Doctor produced a gas in the TARDIS laboratory which made them as peaceful as lambs. Later, the Third Doctor reproduced the gas in the Arkwood Private School chemistry room to counteract the effects of Cedric Mathews' change drug. (COMIC: The Arkwood Experiments [+]Loading...["The Arkwood Experiments (comic story)"])
