I fancy that I can see your forehead wrinkling a little here; so let me explain myself in a parable. There is an old story, familiar in the hospitals, of a bygone practitioner whose simple habit it was to tie a piece of string about the waist of his patient. He would then ask the sufferer to locate the pain. If this were above the string he administered an emetic, if below a purgative; while if the pain and the string coincided, the unhappy victim would receive both. Now it is melancholy to reflect that this gentleman has never been without disciples. And yet how difficult at times may it become to avoid such a fate. Are you prepared to avoid it? Let me put the question in yet another shape. Some day a patient will come to you--you may be quite certain that he will--at the end of a long round or an exhausting afternoon at hospital; will complain to you of his lamentable depression of spirits, his entire loss of appetite, his slight but continual headache; and will show you, in confirmation of these symptoms, nothing graver, let us say, than a dull eye and a yellowish tongue. You will be tired; you will see at a glance that his subjective troubles are altogether disproportionate to the objective gravity of his complaint, and perhaps justifiably you will send him away happy, or at any rate contented, in the belief that he is a bit "liverish." But are you going to allow "liverish" to satisfy yourself? "Of course not," you reply; and yet, believe me, my son, it will be a very real temptation. Why bother, at a long day's end, to worry your tired faculties into presenting to your mind as exact a mental picture of the man's actual condition as they can draw? Nevertheless, unless you do this, you will be treating him with less respect than your old bicycle in the coach-house; as though, if it should creak or wheeze or begin to run less smoothly, you would merely tell yourself that it was "wheelish," and drop oil at random into its most convenient aperture. Do you begin to see what I am driving at?