Killing mice
Most mice in the higher dose categories died during the test. Those considered unlikely to survive until the next check were taken out into the corridor and crudely killed on the floor by breaking their necks with a ball point pen.
After three or four days the number of mice still alive was counted and an LD50 value calculated (This is the dose at which 50% of the mice would be expected to die when injected with the toxin; it is used as a measure of the strength of the toxin in vials of botox).
All the mice who had not already died were killed at the end of the test either by gassing or having their necks broken. Up to 60 mice at a time were loaded into the gas chamber and killed by carbon dioxide poisoning, a death that is far from instantaneous. According to Wickham's own records, on just one day in July 2009, 989 mice were killed.
