An anecdote about Wright , disclaimed by Wright himself , describes a lecture during which Wright tucked an unruly guinea pig under his armpit , where he usually held a chalkboard eraser : at the end of the lecture , Wright absent-mindedly erased the blackboard with the guinea pig . An anecdote about Wright , disclaimed by Wright himself , describes a lecture during which Wright tucked an unruly guinea pig under his armpit , where he usually held a chalkboard eraser : according to the anecdote , at the conclusion of the lecture , Wright absent-mindedly began to erase the blackboard using the guinea pig .