Sentence:  “Unquestionably his metabolism is unduly susceptible to stresses resulting from the interaction of external excitations,” he said, and Bobbie patted him on the shoulder in a maternal sort of way, a thing I wouldn't have cared to do myself though our relations were, as I have indicated, more cordial than they had been at one time, and told him he had said a <WSD>mouthful</WSD>. 
Meaning of the word marked with <WSD> tags:  Quite a bit.