anchor: Unfortunately, I have no proof beyond my surmise, unless ” ” With sudden energy, he caught me by the arm, and whirled me down the hall, calling out in French in his excitement: "Mademoiselle Dorcas, Mademoiselle Dorcas, un moment, s'il vous plait!" Dorcas, quite flurried by the noise, came hurrying out of the pantry. 
positive: The he in this line was so excited he slipped into French.
negative: The speaker spoke in English.