Auenbrugger's and Laennec's observations were made on exactly the same sort of clinical material. They were both studying advanced cases of tuberculosis in the hospitals of a great city. Laennec's work was actually not anticipated in the slightest degree however. How Auenbrugger could have made the careful examinations of the chest that he did in thoracic diseases without acquiring some knowledge of the value of the further application of the sense of hearing, which Laennec was to employ so fruitfully in the diagnosis of affections of the lungs and heart, seems to us almost impossible to understand. Discoveries once made, however, always seem so obvious that the wonder is they were not made long before. It takes genius to cross the line into the realm of the hitherto unknown, and the contemporary generation usually occupies itself mainly with making little of the new discovery. Even genius very rarely makes more than one original observation in a lifetime, and it would be too much to expect more from Auenbrugger. {67} The preface to Auenbrugger's little book is a model of concise directness typical of the man and his ways. As the modest introduction to a work that will ever be a classic in medicine it seems to deserve a place here: "I present to you, kind reader, a new sign for the detection of diseases of the chest, which I have discovered. It consists in the percussion of the human thorax and the determination of the internal condition of this cavity by the varying resonance of the sounds thus produced. My discoveries in this subject are not committed to paper because of an itch for writing, nor an inordinate desire for theorizing. Seven years of observation have put the subject in order and have clarified it for myself and now I feel that it should be published. "I foresee very well that I shall encounter no little opposition to my views and I put my invention before the public with that anticipation. I realize, however, that envy and blame and even hatred and calumny have never failed to come to men who have illuminated art or science by discoveries or have added to their perfection. I expect to have to submit to this danger myself, but I think that no one will be able to call any of my observations to account. I have written only what I have myself learned by personal observation over and over again, and what my senses have taught me during long hours of toil. I have never permitted myself to add or subtract anything from my observations because of the seductions of preconceived theory.