Auenbrugger"s discovery consisted in recognizing that diseases of the chest can be distinguished from one another and their varying character differentiated by the sounds elicited when the chest is tapped with the finger. To this tapping he gave the technical name, since become cla.s.sic in medicine, of percussion. Wherever there is air in the chest, that is all over the healthy lungs, the sound elicited by percussion resembles that given out by a drum over which a thick woolen cloth has been placed. Over the heart, where there is no air, the sound given out, when the chest is percussed, corresponds very nearly to the sound produced when the thigh is tapped. The sound elicited by percussion of the thigh Auenbrugger took as the standard of dulness and applied to it the term Schenkel-ton, or thigh sound.
When the lungs become consolidated because of an inflammatory process such as pneumonia or tuberculosis, then the percussion note over the consolidated area resembles the sound over the leg or that found over the heart. As a rule the heart is somewhat covered by the lungs, and the sound produced by percussion over it is not quite as dull as that over the solid muscular structures of the legs. Whenever fluid finds its way into the thorax, as in pleurisy, then the sound produced on percussion is very dull.
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Auenbrugger further showed that by means of the sound thus obtained he could demonstrate the size of the heart under varying conditions, and so determine whether it is larger than normal or not. This gave the first inkling as to the discernment of hypertrophy and dilatation of the heart, and was the first step in the modern differential diagnosis of heart diseases. He showed, moreover, that he could, by percussion, outline very exactly the extent to which a consolidation of the lung has taken place, or the height to which an effusion into the pleural cavity reaches. These conclusions and demonstrations require not only the greatest care but the most deliberate confirmation of every detail by comparison of the diagnosis during life with the condition found after death in fatal cases.
Auenbrugger seems to have spared neither time nor labor in this work of confirmation. He made a number of experiments upon dead bodies, injecting fluid into the pleural cavity and then demonstrating by percussion the line of demarcation that indicated the level of the fluid within the chest, as well as the pulmonary conditions that developed because of its presence. In the study of pneumonia and tuberculosis particularly, Auenbrugger spent many hours of patient investigation during his ten years of hospital service. He succeeded not only in demonstrating the presence of consolidation, but also the existence of cavities in the lungs and their size and general character.
Vienna was an ideal place for the development of Auenbrugger"s ideas of confirmation. At this time, it must have been one of the most unhealthy places in Europe as regards pulmonary diseases. The city was surrounded by walls that occupied the ground now taken up by the magnificent Ring Stra.s.se and the inhabitants were packed into extremely narrow quarters, The modern munic.i.p.al sanitary {64} conscience is lax enough in our own day, but at that time it had not been awakened to the slightest sense of duty toward the citizens.
Narrow, wandering streets lined by high buildings that made an attache of the British Legation of Vienna speak of the houses of the city, scarcely more than fifty years ago, as "well-like," were the universal rule.
It must be remembered that the present magnificent Austrian capital, containing, perhaps, the handsomest single street and some of the finest buildings in the world, is entirely a creation of the last half-century. The old city had every cause to be unsanitary. Situated in the valley of the Danube, liable in the spring-time to serious floodings from the capricious, mighty river, which has been brought under control only in recent years at great expense; in an exposed situation, which makes it a veritable temple of the winds during the autumn and winter; it is not surprising that tuberculosis should have been very frequent. Even with all its improvements in recent years, sanitary, hygienic, munic.i.p.al and domiciliary, Vienna has at the present time one of the highest death rates from tuberculosis in Europe. In Auenbrugger"s time there must have been practically unlimited opportunity for the study of pulmonary diseases of all kinds.
How well the brilliant young medical observer took advantage of the opportunities thus afforded him can be judged very well from the pa.s.sages of his book that refer to chronic pulmonary diseases. He divides the chronic diseases of the thorax in which abnormal percussion sounds are heard into two cla.s.ses. In the first place, he places those in which the thoracic organs are rendered less capable of resisting disease and become actually affected, because of insidious influences, such as hereditary conditions, depressing circ.u.mstances, poverty and poor nutrition. Without really calling it tuberculosis, it is evident that in this group pulmonary {65} consumption is included.
The second cla.s.s consists of affections in which the thoracic organs become diseased from definite, easily recognizable causes. Such are disturbances of the general health in pulmonary affections that follow thoracic disease not completely recovered from. By these diseases Auenbrugger evidently intends cases of pneumonia or other affections of the lungs, or trauma and the like, which are followed by tuberculous processes.
With regard to cavities in the lungs, Auenbrugger was able not only to demonstrate their presence and to show by autopsy records that his localization and determination of their approximate form and size were correct, but he also understood the method of their formation and explains the reasons for certain varieties of cavities that occur. He speaks of two cla.s.ses of cavity formations. From one kind there is an ichorous discharge; from the other variety the evacuations are purulent. Cavities with non-purulent secretions are situated only in the lung. Abscesses of various kinds--that is, cavities with purulent secretions--may occur in any part, or in any of the organs of the thorax. The lung cavities are usually due to the breaking down of what he calls crude tubercles. Both kinds of cavities may either be closed or have an opening into the bronchi.
Auenbrugger showed very well how to distinguish, by percussion, cavities of various kinds, and set it down as a principle, that before the evacuation of the contents of the cavity percussion over it gave a distinctly dull note, resembling that obtained when the thigh is percussed, while after evacuation, as by copious expectoration, a distinctly resonant note occurred. It is clear from his discussion of the symptoms noted in cavities (at least in the opinion of Dr.
Merbach, who wrote a sketch of Auenbrugger"s life for the Jahresbericht der Gesellschaft fur Natur und Heilkunde in Dresden, {66} in 1861), that Auenbrugger was very near the discovery of auscultation in his study of pulmonary cavities. Auenbrugger says that when a cavity has been located by means of percussion, if the hand be laid over the place beneath which it lies and the patient is asked to cough, the fremitus produced by the pus in the cavity can be felt as it moves under the coughing impulse. This is what we now know as palpation. If instead of using his hand Auenbrugger had applied his ear to the chest, auscultation would have been discovered nearly half a century before Laennec began his work upon the subject. Perhaps Merbach, who was himself a native of Styria and a professor at the University of Gratz, was for patriotic motives more ready than others might be to give Auenbrugger credit for practically discovering auscultation.
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 antic.i.p.ated 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.
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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 cla.s.sic 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 antic.i.p.ation. 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.
"I would not wish, however, that any one should think that this method of diagnosis, which I suggest, has been developed to its utmost perfection. I confess with all candor that there are defects in the system which conscientious observation will, I hope, amend with time. It is possible that there are even other important truths for the recognition {68} of disease still hidden from this method of diagnosis. Some of these may prove of great usefulness for the differentiation, prognosis and cure of diseases of the chest.
"This was the reason why in my personal experience, after I had succeeded in finding the signs in the chest and proceeded further to the investigation of their causes so far as my own observation could help me, I have always afterward had recourse to the commentaries of the ill.u.s.trious Baron Van Swieten, since I have considered that whatever can be desired by an observant man is sure to be found in his work. I have thus been able to spare you a long disquisition. I have found in his work a sure basis of knowledge on which my slight superstructure may be raised up to view.
"I do not doubt, however, that I have accomplished a work which will earn the grat.i.tude of all true devotees of the art of medicine, since I have succeeded in making clear certain things which shed not a little light on our knowledge of the obscure diseases of the chest, a subject hitherto very imperfectly understood.
"I have omitted many things that seem doubtful because they are as yet not sufficiently elaborated. I shall endeavor, however, faithfully to devote myself to [literally to sweat over] the further development of these points. Finally, it has not been my effort to write in any elegant diction. I have chosen a style in which I may be thoroughly understood.
_Vale;_ "December 31, 1760."
Auenbrugger"s own realization of the importance of his work and of its significant value for medicine kept him faithfully investigating his chosen subject, though he seems to have met with very little encouragement from members of {69} the medical profession near him. It is extremely difficult to understand how his practical observations and thoroughly conservative claim failed to attract more attention than they did from really great physicians who were deeply interested in the progress of medicine. At least two distinguished writers on medicine, Van Swieten and De Haen, compiled treatises on medical subjects that included the consideration of diseases of the chest within a few years after Auenbrugger"s _Inventum Novum_ appeared, and yet neither of them devotes any s.p.a.ce to the question of percussion nor hints at its possible value.
Van Swieten"s work consisted of commentaries upon the aphorisms of Boerhaave. The Vienna professor did not, however, limit himself to the consideration of the aphorisms alone, but made his work also a compendium of his own clinical experiences with acute and chronic diseases. As a matter of fact his commentaries on the aphorisms are each a monograph on some special disease. The two last volumes of this commentary appear after the publication of Auenbrugger"s book on percussion, one volume being published in 1772, the other in 1774.
The first of these articles contains a long article on pulmonary consumption, and the other an almost equally long chapter on pleurisy with effusion. In neither of the volumes, however, is there any mention of percussion, or of Auenbrugger"s work, though if Van Swieten had given any serious attention to the subject, he must have become convinced how valuable Auenbrugger"s invention was in the diagnosis of these conditions.
This omission is all the more surprising as Auenbrugger was a pupil of Van Swieten"s and practically dedicated his _Inventum Novum_ to his master. He mentions Van Swieten"s work several times in his little book. Auenbrugger"s {70} investigations were not unknown to Van Swieten then, and the only conclusion to be drawn from his neglect to mention Auenbrugger"s methods is that he deliberately omitted reference to them because of his failure to recognize the value of the discovery. This const.i.tutes one of the most serious blots on Van Swieten"s medical career. He was succeeded as the head of the clinic in Vienna by De Haen, who also came from Leyden and brought with him the methods of Boerhaave"s clinical school. As the time during which Auenbrugger was making his valuable observations at the Spanish military hospital coincides with the years when De Haen was professor of clinical medicine, and when he was frequently indebted to his colleague of the Spanish hospital for his cases for demonstration, it is impossible to conceive that Auenbrugger or his work should have remained unknown to the distinguished head of the clinic.
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 princ.i.p.al 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 Gottingen, 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.
Other medical writers of the time perhaps, as the result of reading Professor Vogel"s book, made the same mistake {72} in their appreciation of Auenbrugger"s work. Vogel himself insisted that Auenbrugger did wrong to claim any originality for his invention, since it had been used so long before by Hippocrates. He adds that what is original with Auenbrugger is of very little value, the older ideas being the only ones worth while considering with regard to the application of this so-called new method of diagnosis. Vogel was an authority in medicine at the time and other commentators took the key note from him in this matter, and in many parts of Germany it was generally accepted that Auenbrugger"s method of percussion was only an elaborated method of the so-called succussion of Hippocrates.
Under these circ.u.mstances it is perhaps not surprising that Auenbrugger"s work attracted very little attention in the German-speaking countries. In Vienna itself, as we have already said, Van Swieten and De Haen failed utterly to recognize its value. Outside of Vienna their example was naturally followed, for the Vienna school was considered authoritative, and surely, if any one, the professors of the University of Vienna might be expected to know whether Auenbrugger"s new discovery was really of any value or not.
It is interesting to compare Auenbrugger"s state of mind, with regard to the neglect of his discovery, with Laennec"s remark in the preface of his book. Laennec said: "For our generation is not inquisitive as to what is being accomplished by its own sons. Claims of new discoveries made by contemporaries are apt for the most part to be met by smiles and mocking remarks. It is always easier to condemn than to test by actual experience." Auenbrugger seems to have suffered from more than the neglect of which Laennec complains. When he speaks of envy and calumny in no uncertain terms, the only conclusion possible is that his representations as to his discoveries must have been set {73} down as pretensions that his contemporaries considered unjustified by what they knew of his work.
It is interesting also to note that both men found their prospects of reward, not in the good will of their contemporaries, nor even the prospect of fame, but in the hope that their work would be useful in lessening the sum of human suffering. Laennec said: "It suffices for me if I can only feel sure that this method will commend itself to a few worthy and learned men who will make it of use to many patients. I shall consider it ample, yea more than sufficient reward for my labor, if it should prove the means by which a single human being is s.n.a.t.c.hed from untimely death."
Laennec"s words are almost an echo fifty years afterward of Auenbrugger"s expressions, just quoted: "I console myself," he said, "with the thought that I have accomplished a work which will earn the grat.i.tude of all true devotees of the art of medicine, since I have succeeded in making clear many things which shed not a little light on the chapter of the obscure diseases of the chest, in which our knowledge has. .h.i.therto been so very incomplete."
As a rule it may be said that medical observers whose genius leads them to step across the narrow line that separates the known from the unknown are likely to lack the appreciation of their own generation.
Long before Auenbrugger or Laennec, Harvey, the discoverer of the circulation of the blood, said to friends that he did not expect any one of his generation to accept the new doctrine, and it is well known that the great medical men of the time did not accept it. Harvey is not an isolated example, and even in our own time real medical progress sometimes waits for years for recognition, while well-advertised pretended advances are occupying the centre of the stage. Auenbrugger"s discovery made its impress, however, and was never entirely lost to sight. Even {74} before his death there was the consoling prospect of its meeting with adequate attention.
De Haen"s successor in Vienna, Maximilian Stoll, treated Auenbrugger"s work very differently from his predecessors, and was the first to introduce it practically into clinical medical training. Stoll did not hesitate in his clinic, on the strength of what was discovered by means of percussion, to attempt the evacuation of fluid from the pleural cavity on a number of occasions. It can be easily understood that with their lack of knowledge of the necessity for thorough cleanliness in the surgical sense, such an operation might readily be followed by discouragingly fatal results. This actually happened in Stoll"s own experience. He does not, however, seem to have abandoned his practice of tapping the chest because of this. He insisted to his students that Auenbrugger more than anyone else had experience in removing fluid, and especially purulent collections, from the chest, and he recommended the practice to them. He added that medicine owed as much to Auenbrugger for his rational method of treating effusions into the pleural cavity, whether of pus or serum, as for his diagnostic sign by which the presence of the fluid could surely be recognized.
Some of Stoll"s pupils took up the work of commending Auenbrugger"s method, and a little book written by one of them, Eyerel, came into the hands of the distinguished French physician, Corvisart. Eyerel did not hesitate to say, in his treatise on empyema, that the practice of percussion of the thorax, a diagnostic method introduced by the very distinguished Vienna physician, Auenbrugger, had been of great help to them in the study of this disease.
Once the great French professor of medicine, Corvisart, took it up, the new method of diagnosis was destined to have an immediate and world-wide vogue. Corvisart was not {75} only a power in medicine because of his faculty of observation and his thorough appreciation of the work of others, but he was the court physician of the first Napoleon, and this gave any ideas that he favored many advent.i.tious chances for publicity. Napoleon"s well-known faculty for selecting men for special positions whose genius was calculated to be of service to him was never less at fault than when he violated most of the court medical traditions in Paris and chose Corvisart for the imperial physician. Corvisart"s selection was the result of Napoleon"s appreciation of his new method of diagnosis, namely, that of percussion, in chest diseases.
The Emperor himself was suffering from a persistent cold and was told that Corvisart, instead of following the traditional method of feeling the pulse, looking very wisely at the tongue and then gazing learnedly into s.p.a.ce, conducted an actual examination of the chest and sounded it carefully all over, in order to determine where abnormal conditions might exist. This struck Napoleon as a very practical and possibly valuable feature of diagnosis. Accordingly Corvisart was summoned to give his professional opinion. After the consultation he was made the Emperor"s private physician. When Corvisart took up the subject of percussion of the chest, it was practically unknown in Europe outside of Vienna. Even in the city of its origin, as we have seen, it was not well appreciated. Auenbrugger"s little book had fallen into oblivion.
Corvisart obtained his hint as to the possible value of percussion from Stoll"s and Eyerel"s appreciative remarks with regard to it. The Frenchman used the method to some extent and, realizing its value, resolved to call the attention of his countrymen and the medical world to this very helpful aid in diagnosis. It was at this time that he came upon Auenbrugger"s original monograph. Instead then of writing himself on the subject, he translated {76} Auenbrugger"s little book into French and made a commentary on it.
Corvisart was Laennec"s patron in medicine, his favorite teacher, and the man to whom the great French physician owed much of his early inspiration. It is no little merit in Corvisart"s career thus to have been the connecting link between the men who did most for the practical science of medicine, and especially for the important but obscure chapter of diseases of the chest. He did not attempt at all to claim for himself any of the merit that he felt should rightfully go to Auenbrugger, and while his own observations and writings established percussion upon a firm basis and extended its knowledge, he shares the immortality of his discoverer, and comes down to us in medical history as an example of the reward of having rendered faithfully what was due, where it was due. It has been the custom to praise Corvisart for his justice toward Auenbrugger. Mere justice seems scarcely a worthy reason for praise of a great man, yet the history of medicine is so full of failures on the part of subsequent observers to acknowledge priority of discovery, that perhaps the praise does not seem quite as futile as it otherwise would.
It is not surprising then that Corvisart"s pupil Laennec should have appreciated very thoroughly the value of Auenbrugger"s discovery. In the preface of his book on Mediate Auscultation, Laennec bewails the fact that men are generally neglectful of discoveries made in their own time, and fail to give them the attention they deserve. He attributes this neglect rather to the well-known carelessness of men than to any deliberate failure to recognize the merit of contemporary work. He says:
"Lack of attention is an extremely common failing of all men. What it takes years and hard labor to acquire, is not {77} infrequently pa.s.sed over without notice. Auenbrugger"s method, published some fifty years ago, though capable of being learned in a few days, and without difficulty, and of being put into practice without the use of any instruments, although s.n.a.t.c.hed from oblivion by my ill.u.s.trious preceptor, Professor Corvisart, and made clearer than it had been left even by the author himself, is not as yet in ordinary use among physicians. Even the wonderful invention of the ill.u.s.trious Jenner, though received with so much praise, and with regard to whose efficaciousness numberless confirmatory observations have been made, is already somewhat less prominent in the minds of men than it should be, or at least it would be, only for the fact that the governments of many countries, provinces and cities, the foresight of the clergy, of the authorities of all kinds, and the advice of the best physicians have exerted all their influence to keep it at public expense constantly in practice."
After about ten years of service at the Spanish military hospital, Auenbrugger resigned his position there and took up private practice.
In this he was eminently successful, being, as might be expected, especially in demand for cases involving affections of the thorax. His practice appears to have been to a great extent among the better cla.s.s of people, but he seems never to have neglected the poorer patients whom he had come to know during his hospital experience. There are traditions in Vienna of his unfailing willingness to a.s.sist the poor and even to put himself to considerable inconvenience in order to be of service to them.
Tradition tells that he was very conscientious in the pursuit of his vocation as a physician, and among the family relics there is preserved a small lantern which he kept always by his bedside, to light him on his visits to the sick when called out at night. It must not be forgotten that city streets {78} were not regularly lighted at the end of the eighteenth century, and night calls even in city work must have been a source of great annoyance and discomfort. There is a family tradition, too, that the night bell at his house was connected directly with Auenbrugger"s room, so that the others of the household might not be disturbed when night callers came for him. Every tradition points to him as a man among men in his unselfish readiness to save others trouble, and do all the good in his power.
Auenbrugger was, according to well-grounded traditions, especially admirable in his relations toward other members of the medical profession. This may not seem a very significant sign of amiability to those outside the profession, but it is well recognized that even great physicians have not always been known to get on well with brother pract.i.tioners. Auenbrugger has, besides, the pleasant reputation of having been of great material a.s.sistance to a number of needy medical students during the time of their university careers, and to have frequently lent a helping hand to young pract.i.tioners in the city, who probably found it quite as discouraging, beginning practice in those days, as any of their young confreres of this generation find it at the present time.
To physicians and medical students when ill, Auenbrugger was almost unceasing in attention. Two or three physicians of the generation immediately after his attributed to his unselfish care and devotion to them their recovery from what would otherwise have been mortal illnesses. In this way Auenbrugger seems to have been a man whom everyone who came to know him, even slightly, learned to love and respect. His relations to his family and relatives were always of the most happy, kind character, and family traditions show that his fatherly care was befittingly returned to him in his old age. The number of his friends was very great, {79} and he counted among them some of the most distinguished inhabitants of the Austrian capital.
Notwithstanding his devotion to his practice, Auenbrugger did not cease to make observations that occasionally he considered worthy of being committed to paper. He was especially careful in the study of his cases, and left fully written records of over 400 important cases that he had studied very faithfully. His attention seems to have been attracted particularly to certain mental diseases. This work was done half a century before even the first beginnings of the modern cla.s.sifications of mental diseases were attempted. He wrote a short article with regard to mania and its treatment, and a longer article on melancholia. How well he recognized the essential feature of this latter affection and the main symptom that must be guarded against, can be gathered very well from the t.i.tle of his paper, which he called "The Still Madness, or the Impulse to Self-Murder."
It is about the time that he was engaged in the study of melancholia, perhaps as a contrast to sadder things, that he wrote a comic opera, of which we shall have more to say presently. His description of the conditions that he saw during an epidemic of dysentery that occurred in Vienna show how exact and careful a clinical observer he could be, and that the demands of his practice did not absorb all his attention to the detriment of his faculty for observation. He seems himself to have suffered from a severe attack of typhus fever which raged epidemically in Vienna in 1798.