Out of this further inquiry arises one of the greatest and most common sources of fallacy ; and it is great in proportion as the history and sensations of the patient become the sources of mformation, and the alterations in struc ture or function of which we can take cognizance are few and indistinct. It springs from the necessity of framing an hypothesis of the disease from the general outline already given of the case, and the anticipation arising out of this hypothesis, that certain phenomena ought to be present : in consequence of this persuasion, interrogatories assume the form, more or less, of leading questions, unconsciously to the inquirer himself; and this cannot fail to bias the mind of the person to whom they are addressed.
This preliminary investigation le,ads to the association of symp toms according to their order Of sequence, and we must be careful, by observing them from another point of view, to correct any false impression to which it may have given rise. While, there fore, we follow the patient telling his own case in his o wn way, it is quite essential that we should make a subsequent and inde pendent investigation of existing symptoms according to some systematic course, which shall have the effect of ranging them in such scientific groups as may most readily and naturally lead to the detection of the cause which best accounts for their origin, and most fully satisfies all the requirements of the ease.
In seeking for such an arrangement, we find that there are two great classes of indications, the general and the local ; each of these comprehending two divisions, the subjective and the objec tive, the sensations of the patient, and the alterations in structure or function of which the observer can take note.
It may be useful to notice here that different names are assigned to these phenomena, as the indications which they afford happen to be derived from perversion of vital functions, or from altered relations of parts to each other, or to the external world. These are known by the names respectively of vital symptoms and physical signs : thus, pain is one of the symptoms, while swell ing and redness are among the signs of local inflammation; cough and expec toration represent the symptoms, the fioises produced by the meeting of air and fluid in the bronchial tubes are the signs of bronchitis. I believe this division was intended originally to mean much more than this ; it was believed that every disease had not only its category of symptoms, which might, any or all of them, be common to it with other diseases, but that each had for itself its peculiar distinguishing sign or mark, by which it was as readily recognized as by its name (for instance, the Ale crepitant for pneumonia, the rale sous-crepitant for pulmonary oedema, &c.). But we shall find as we pro
ceed that the absence of the sign does not imply absence of the disease, and its presence affords at best only a strong presumption in favor of a certain condition of parts.
If general and local indications could be arranged so as to correspond to general and local diseases, it would be enough to discuss them in this order; but the two are so inextricably min gled together, that no more can be done than merely to adopt, so far as possible, the plan of taking general indications first, and special indications afterwards; for we must often reconsider the general symptoms in investigating local disease, as we must also frequently anticipate special signs in inquiring into conditions of general disorder. No observation can be considered complete which has not taken note as well of the general state of the patient as of the particular condition of each individual organ, under both these aspects; and however we may endeavor to sim plify the inquiry, omissions can only be avoided at the expense of occasional repetition. It will constantly happen in practice that the same indication which has been already noted in regard to duration and sequence, must again be reviewed both in its bearing on the general condition of the system, and also in its relation to lesions of particular organs.
When the student is introduced to the bedside of the patient, it is of great importance that he should carry in his mind a cer tain definite course of inquiry, according to which he should endeavor to trace out a faithful history of the case, so that with out any guide but his own investigation, he may be able to frame a history which will leave him in little doubt as to the depart ment in the theory of disease to which it ought to be referred.
We are at present only engaged in inquiring into the uses of such an investi gation, in so far as it leads to a correct diagnosis; but every one of the separate features in the picture may be of importance in determining the treatment. Even when a correct diagnosis is formed, various remedies will suggest them selves to the mind of the practitioner as equally applicable, and theirjudicious selection very often depends upon a due consideration of the antecedents and peculiarities, much more than upon the name given to the disease, or the place it may hold in a scientific classification. . .