We have said that one of the greatest difficulties, perhaps the greatest that is encountered in the use of a fundamental axiom in therapeutics, comes from the impossibility of applying, rigorously, a past fact in treatment to a case in hand ; in other words, whatever precision may be obtained in diagnosis, whatever may be the degree of similarity that exists between two pathological states, as there is never identity between them, it follows, that a course of medication which has succeeded perfectly in one case, may, strictly speaking, fail in another.
It is not less evident, that the best means of avoiding, or rather of diminishing this permanent cause of mistakes, consists in
perfecting, more and more, the diagnosis of diseases, so as to give it the highest degree of exactness possible. By this means, on the one hand, the confounding of essentially different morbid states will be avoided ; and, on the other, the distinction of others but slightly differing in aspect, be established.
The importance of diagnosis once recognized, as it has been by the great physicians of all ages, there is no effort that the mind has not made, no expedients that have not been attempted, in order to give it the highest perfection possible.
The first plan suggested to the minds of observers was, to take account of all the symptoms that presented themselves in the course of the disease, and to record them in regular succession, as they appeared. According to this plan, a great number of nosological tables were formed, so that for any disease, a comparison of the phenomena that appeared was made with the symptomatic tables that had been framed, and from this comparison an appropriate treatment was deduced.
This method, which appears, at first sight, so natural and exact, is, at bottom, extremely defective. In the first place, it has the serious inconvenience of attributing an equal value to all the symptoms, while daily observation proves that notable differences exist. In the second place, a long enumeration of morbid phenomena, recorded one after another, without choice or discernment, is no more a portrait of a disease, than colors, thrown at hazard upon the canvass, that of a person sitting for a likeness ; lastly, all classification of diseases becomes impracticable on this plan, for, before attempting a work of this kind, it is necessary to inquire how many analagous symptoms would be required to place two affections in the same class, and assign them a like treatment ; it would be absurd to attempt to answer the question.
Thus we see that there is no pathological classification possible, by a simple enumeration of symptoms, yet, nevertheless, without the aid of a classification, the practice of Medicine is a mere groping in the dark, and does not merit the name of Art. Without the advantages of a classification, the physician may justly be likened to a blind person armed with a club, and striking indifferently at the disease or at the patient.
Hippocrates strongly felt the errors of this manner of observing and describing diseases, when he reproached the Asclepiadoe of Cnidus for having adopted this plan, which led them to multiply, innumerably, the division of diseases. "Those who have collected," he says, "the sentences that are termed Cnidian, have well traced the morbid symptoms as they are exhibited, as well as the manner in which certain affections terminate ; but any one may do as much as this, without being a physician, by asking sick persons the symptoms they experience. Much has been neglected in the Cnidian sentences, which it is important for the physician to know, without questioning the patient, and which is essential to the exact appreciation of the disease. Some were not ignorant, however, of the various characters of diseases, and their different forms, but erred whenever they attempted to make a rational classification. Such errors are easily committed, if distinctions are made in diseases from mere shades of difference, and if other names are given to all those which are not exactly identical.(Traite du Regime dans les Maladies Aigues," Â§ 1, II, traduc. de Gardeil)
It is thus well demonstrated that all the symptoms of a pathological state are far from having the same degree of importance. This is almost a trivial statement to make to physicians ; only dull dreamers and their stupid adepts, can have classed together a frightful headache and a simple wrinkling of the forehead, an intense gastralgia with an itching of the lobe of the ear. Posterity could not believe that such absurdities were ever perpetrated, if there were not authentic documents to attest it.(Such, and even more silly statements are found in Hahneman's " Materia Medica)
From the moment that the necessity was felt of making a choice among morbid phenomena, they have been divided into durable and transient, essential and accessory, primary and secondary, etc. Then commenced the discussion on the essence of diseases, their causes, signs, march, termination, etc. Thence, in short, sprung Medical Philosophy, and with it, systems of Medicine.
From History of Medicine by P.V. Renouard M.D.