Eleanor Harris of New Scientists has a list of 8 scientists who subjected themselves to their own funny (and gross) experiments. Take, for example, German surgeon August Bier who did this experiment in 1898 while working on spinal anesthesia:
To find out, Bier decided to be anaesthetised himself. But things didn't go as planned for Bier – or for his hapless assistant, Augustus Hildebrandt.
Hildebrandt was supposed to administer the cocaine but, thanks to a mix-up with the equipment, Bier was left with a hole in his neck from which cerebrospinal fluid began to flow.
Rather than abandon the effort, however, the two men switched places. Once Hildebrandt had been anaesthetized, Bier stabbed, hammered and burned his assistant, pulled out his pubic hairs and – presumably eager to leave no stone unturned in testing the new method's efficiency – squashed his testicles.