Itremblingly considered a moment, and then the devil of temptation provoked me to say: —

‘well—to—to—be entertaining, i thought.’

this was a red rag to the bull. he raged and stormed so (he was crossing the river at the time) that i judge it made him blind, because he ran over the steering-oar of a trading-scow.

what does the expression “a red rag to the bull” suggest?