Control
Permanent link to this comic: http://xkcd.com/790/
Image URL (for hotlinking/embedding): http://imgs.xkcd.com/comics/control.png
A man looks down at his arm calmly, while next to him a woman is violently flailing around in terror. In the foreground, two scientists, one holding a clipboard, look on in puzzlement.
Man: My rash seems to have shrunk by about 20% today.
Woman: OH GOD SPIDERS
Scientists: ???
{{Title text: Which, at one point, led to a study showing that LSD produces no more hallucinations than a placebo.}}