METHOD OF DIAGNOSIS.
THE discrimination of disease, as we have attempted to show, proceeds upon a knowledge, more or less complete, of all the phenomena which any given case presents. When it has termi nated in the recovery or death of the patient, the series of events arranged in a definite and intelligible order, from their com mencement to their conclusion, is comprised under what is called its " History," which ought to present to the mind a perfect pic ture of all its important features. Unfortunately, the perusal of the clinical case-books of an hospital, or even the published reports of cases by our best authors, must convince us how little the real meaning of the history of a case is understood. With out the key of a knowledge of the disease, derived from some extraneous source, it will be found too often impossible to form a correct diagnosis. Many of the difficulties are inseparable, to a certain extent, from the nature and sources of the information, but many are due solely to want of system and arrangement.
The history divides itself naturally into two parts : the report of the patient himself or of his friends and attendants, of what happened before he was seen by the physician; and the pheno mena actually observed at the time of examination : the same distinction must be made between events occurring in the absence of the observer, and those noted at any subsequent visit. But as our object is rather to point out the true principles on which diagnosis is based than to give the history of diseased states, only casual reference can be made to ulterior changes, and, in general, it must be presumed that the previous history is learned by re port, while the signs and symptoms are investigated as they pre sent themselves on a first examination.
The previous history is often of great importance ; it ought to commence with the very first deviation from health, in so far as the sensations and functions of the patient are concerned, and it ought to give a connected account of the changes which have subsequently passed upon these, and the origin of new symptoms. This account is of itself sometimes sufficient to point out the na ture of the malady. It seldom happens that all the particulars are correctly detailed, yet such as it is, this statement must very often be appealed to m reference to the duration, and order of sequence of particular symptoms, with a view to determine their immediate precursors, and the phenomena which have appeared to follow upon, or spiing out of t'hem. Practically it will be found
that the more perfect this information is, whether limited to the present illness, or extended to a perfect acquaintance with pre vious ailments, the more valuable does it prove as an aid to diag nosis.
Much care is necessary not only to get at the first deviation from health, but also to avoid being led sway by a preconceived idea in the mind of the narrator, and the more so if coming from a scientific person. So much does the mind seek after causes of all natural phenomena, that the simplest and most illiterate patient is more ready to broach a theory of his illness, than to tell his sensations or his sufferings.
It is also to be remembered, that although disease has a distinct and intel ligible history, because it follows a definite course, yet the story of the patient is often inconsistent with itself. General inconsistency on all points 18 com monly an evidence of imaginary, hypochondriacal or hysterical maladies. Partial inconsistency may arise from tile existence of different diseases, either simultaneously or at successive periods, and the misplaced association of the symptoms belonging to each, or simply from incorrectness of observation.
Sometimes the narration of past sensations and sufferings may t,end to lead the observer away from the true seat of the malady, inasmuch as not unfre quently disease of central organs first makes itself known by symptoms in remote parts. Against this there can be no safeguard but a thorough know ledge of the relations subsisting between morbid states and the possible phe nomena which may attend upon them. Again, symptoms of importance may be forgotten, and circumstances which must greatly influence our opinion on the case may have been omitted, and these pomta must be inquired into. The same knowledge of the associations of morbid states and their phenomena leads us to ask such questions as may determine whether the symptoms de tailed have been caused by one condition or another (e. g., whether pain has been caused by inflammation from the knowledge whether fever has been pre sent or not).