CHAPTER I. Uses of Classification in the Study of Disease; Comparison of (Part 2)

sounds produced by the passage of air and of blood within the thorax, or the resonance of the air when thrown into motion by the act of speaking, seem comparatively difficult, and involve more complicated phenomena. The same remarks are applicable to the signs of percussion, which are not a little difficult; but in either case, the sounds are regularly and uniformly the same under similar circumstances. The difficulty in learning the physical signs thus consists in two distinct points ; first, in the acquisition of the sounds them- selves, considered as simple phenomena; secondly, in the know- ledge of the condition of the organs which corresponds to these sounds. The sounds themselves require not only to be learned well enough to be understood, but they must be fixed so thoroughly in the mind that noroom should be left for mistaking one for an- other. This demands time, attention, and organs of hearing which are not physically-incapable of discriminating between sounds which at first may seem nearly similar. The first diffi- culty is surmounted; there still remains the other, which requires a knowledge of many circumstances which are connected with the pathology of the disease. These are those which relate to 24 GENERAL AND PHYSICAL SIGNS. the physical condition of the viscera, or the pathological anatomy of the parts, and to the functional action of the organs, which is necessary for the production of most of the sounds. Hence the knowledge of the physical means of exploration requires no little time and attention, and cannot be learned in a careless or hasty manner. There is, therefore, this impediment to the study of the dis- cases of the chest, and of physical exploration, that the act itself is a matter of difficulty, and requires more Jabour than is will- ingly bestowed upon it. Che whole process of investigation requires this attention ; even the manual or mechanical precau- tions necessary to be taken, are not to be learned at the first trial, but require time in the performance of this art, like that of every other; for the car and hand are not at first capable of the delicate and varied actions necessary for the satisfactory exploration of the thor: But, although the apparently com- plex nature of physical exploration may prevent many from at- tempting its study, the difliculties which at first present them- selves are readily enough removed by patient and laborious attention, and are more than compensated by the certainty which results from a mode of investigation based upon fixed physical laws. Every step in the acquisition of this know- ledge is appreciable, and in proportion as it becomes more accurate, the diagnosis of disease assumes a new character, which is never acquired when confined to the functional symp- toms. This is true even at present, when the comparison of local and general symptoms to which I have just alluded has rendered the latter much more clear, and their value better defined. The physical signs have served as a point of depar- ture, with which to compare the rational symptoms, and have thus rendered the latter more easy of recognition, and more positive in their relations with the internal lesions of the thorax. This is so obviously the case, that a. glance at the works of any of the later writers upon the subject, is sufficient to show that the rational signs ha¥e become of more practical service for the study of diagnosis than they have ever been before, and that many of these symptoms have been investigated with a care which was never before bestowed upon them. Some symptoms, GENERAL AND PHYSICAL SIGNS. 25 it is true, have fallen into comparative neglect, because they are no longer-of decided utility in diagnosis, but the greater number have derived new value from their connection with the physical signs. -As the diagnostic characters of the diseases of the chest are composed of several distinct sets of symptoms, they may be studied after each class of them has been separately learned, or the diseases themselves may be first observed, and the symptoms analysed as.they present themselves at the bed-side. The former method is naturally adopted in a systematic treatise, or course of lectures; the latter belongs more properly to clinical or de- monstrative medicine,—a subject of which I treat more at large in another place. As the object of the present treatise is not only to explain the mode of application of these methods of investigation to the study of disease, but to teach the methods themselves, it resolves itself naturally into two parts. The first part will contain the explanation of the physical signs, and teach the method of acquiring them which I have found most conve- nient for the pupil. In connection with this portion of the sub- ject, I shall treat of those functional symptoms which are imme- diately connected with the organs of the thorax, and are there- fore most conveniently learned at an early part of the study. The second part will be devoted to the examination of indi- vidual diseases in connection with their symptoms and treat- ment. The series will thus comprise, as nearly as my time will permit, a complete history of the modes of exploration used in the diseases of the thorax, as well as an account of those dis- eases themselves. The difficulties which attend the study of pectoral diseases, depend more, however,'upon an imperfect method, than upon the subject itself, and may be obviated in a great degree by adopting an order which is in harmony with the natural con- nection of these signs. In all essential particulars they are readily understood when they are pointed out by one who is practically familiar with them; but one who is yet unpractised becomes embarrassed when he examines a patient without the aid of an adviser. Signs which are really different are some- times confounded together, and those which are mere varieties 26 GENERAL AND PHYSICAL SIGNS. of the same species are thought to be perfectly distinct. If the signs are well characterized sounds, their discrimination should always be easy, and error would be impossible. That is, the correspondence between the sounds in certain physical condi- tions is necessarily exact, and the chances of error depend upon an erroneous interpretation of them. ‘The interpretation is very different from the recognition of the sounds, and necessarily in- cludes more data and more complicated reasoning. ‘There can be no reason for not detecting a sound connected with the chest, it should be at least as easily recognised as the tone of voice or spoken language; it does not require any peculiar nicety of organs, or a finely cultivated musical car, but merely a good power of discriminating sounds, and the attention necessary for observation of any natural phenomena. I shall endeavour to arrange the physical signs in such an order as will facilitate this part of the study, and shall explain the method of acquiring them which will be found most conve- nient. ‘The great secret is to give much attention to the signs at first, and fix each one in our mind as we go on. If we con- tent ourselves with detecting them when pointed out to us, and merely understanding the differential characters without actually knowing them, we will gain but little, and we will never acquire the knowledge of them which is practically useful. ‘The best method of avoiding the habit of careless observation, is to dwell long upon each sign at first, and afterwards connect it with others which are closely related to it, and are met with either in the same or in other patients. The whole matter will in this way be rendered singularly easy. CONFORMATION OF THE CHEST. 27