There is not a single mention, however, to be found anywhere in De Haen's voluminous writings of Auenbrugger or his work. De Haen's principal work is his _Ratio Medendi_ (_System of Medicine_), published at Vienna during the years from 1757 to 1779. It consists of eighteen volumes, in which all the important forms of disease as well as the rarer types of affections that came to the clinic are thoroughly discussed. De Haen treated of pneumonia, of consumption, of pleurisy with effusion, which he calls dropsy of the chest, but never suggests the use of percussion. On the contrary, he complains in a number of places how very obscure and difficult of diagnosis are thoracic diseases and especially dropsy of the chest, pleuritic and pericardial exudates, and insists on the ease with which errors of diagnosis may be made in these subjects. He failed completely to recognize how much light had just been thrown on this subject by Auenbrugger's work, and how much easier the differential {71} diagnoses of these conditions were to be as the result of systematic percussion. Some of the commentaries on Auenbrugger's work are not entirely depreciative, however. In Ludwig's _Commentaria de Rebus in Scientia Naturali et Medicina Gestis_ for the year 1762, published at Leipzig, there is an excellent notice of Auenbrugger's work within a year after its appearance. It is not known who the reviewer was, but he calls Auenbrugger's discovery "a torch that was designed to illumine the darkness in which diseases of the thorax had up to this time lain concealed." A brilliant future was prophesied for the new method of examination. It is evident that the writer not only thoroughly comprehended Auenbrugger's work, but had himself applied the percussion method for purposes of diagnosis. This is almost the only favorable and reasonably intelligent review of Auenbrugger's work to be found in the medical journals of the time. In the new Medical Library, issued by Rudolph Vogel, Professor of Medicine in Göttingen, published in six volumes in 1766, there is a short mention of Auenbrugger's book and his new discovery. This reference is, however, an extremely curious affair. The good professor completely failed to understand in what the new discovery really consists. It is clear that he had never read Auenbrugger's book. He seems to have heard of the subject from some medical friend, and to have obtained an entirely wrong notion. He talks of Auenbrugger's new diagnostic method as if it were an imitation of Hippocrates's succussion method of recognizing the presence of fluid in the chest by shaking the patient till the liquid gave the characteristic splash.