"'...one more cup of coffee and I must attend to my calculus, nearly always a difficult subject.'
'So you have suddenly taken to the calculus?' cried Jack. 'How very glad I am—amazed—quite stunned. By just calculus I take it you mean the differential rather than the infinitesimal? If I can be of any help...'
'You are very good, my dear... but I mean the vesical calculus, no more: what is commonly known as a stone in the bladder, the utmost reach of my mathematics.'"