"Men die of the diseases which they have studied most," remarked the surgeon, snipping off the end of a cigar with all his professional neatness and finish. "It's as if the morbid condition was an evil creature which, when it found itself closely hunted, flew at the throat of its pursuer. If you worry the microbes too much they may worry you. I've seen cases of it, and not necessarily in microbic diseases either. There was, of course, the well-known instance of Liston and the aneurism; and a dozen others that I could mention. You couldn't have a clearer case than that of poor old Walker of St. Christopher's. Not heard of it? Well, of course, it was a little before your time, but I wonder that it should have been forgotten. You youngsters are so busy in keeping up to the day that you lose a good deal that is interesting of yesterday. "Walker was one of the best men in Europe on nervous disease. You must have read his little book on sclerosis of the posterior columns. It's as interesting as a novel, and epoch-making in its way. He worked like a horse, did Walker--huge consulting practice--hours a day in the clinical wards--constant original investigations. And then he enjoyed himself also. 'De mortuis,' of course, but still it's an open secret among all who knew him. If he died at forty-five, he crammed eighty years into it. The marvel was that he could have held on so long at the pace at which he was going. But he took it beautifully when it came. "I was his clinical assistant at the time. Walker was lecturing on locomotor ataxia to a wardful of youngsters. He was explaining that one of the early signs of the complaint was that the patient could not put his heels together with his eyes shut without staggering. As he spoke, he suited the action to the word. I don't suppose the boys noticed anything. I did, and so did he, though he finished his lecture without a sign. "When it was over he came into my room and lit a cigarette. "'Just run over my reflexes, Smith,' said he. "There was hardly a trace of them left. I tapped away at his knee-tendon and might as well have tried to get a jerk out of that sofa-cushion. He stood with his eyes shut again, and he swayed like a bush in the wind. "'So,' said he, 'it was not intercostal neuralgia after all.'