The ultimate object of study in all departments of medicine— the object which must ever be kept in view alike by teacher and pupil—is the relief of the patient by the successful treatment of disease. To this end the properties of various remedial agents are taught in Materia Medics, as they possess the power of neu tralizing or eliminating poisons, of counteracting morbid action in its progress or modifying its results, and of aiding and sustain ing the powers of life, when those wonderful laws of our economy come into operation, by which the destructive agency of noxious influences is combated, and the useless and effete or injured tissues are extruded from the body. To the same end the student must acquire a knowledge of the various structures of the body and the functions of its organs in health, as well as the pathological changes in solids and fluids, which become the subjects of anato mical research, and the perversions of healthy function which may be traced at the in the progress of disease : these belong to the domain of Physiology and Pathology. The theory of disease, again, combines, by the aid of experience, the perversion of function with the change of structure, deducing the symptoms observed as a necessary sequence from the disturbance of the laws of health to which such changes must give rise ; but it also teaches us that there are other and more hidden elements of disease, stamped, in their operation on the human frame, with characters no less marked and distinct, which have yet evaded our most diligent search. This department divides itself into two branches. It points out the alliances and differences between various forms of disease and the prominent features by which they are characterized, and to this the name of Nosology has been applied ; while under the name of Semeiology it especially treats of the symptoms of diseased action which each organ or region of the body is capable of manifesting. It is the province of Diagnosis to combine together these various lessons, and by the application of the symptomatology of disease in general to any particular case, to arrive at a just conclusion regarding its true nature and patho logy : and though it does not enter directly on the question of treatment, it has regard to all those indications on which it ought to be based.
In the present imperfect condition of the science of medicine, too much importance can scarcely be assigned to the study of diagnosis, which, in its higher and more intricate departments, by separating the known from the unknown in our experience, may yet point out new relations between morbid phenomena and structural change; and by enabling us to discriminate the finer shades of difference which distinguish various forms of allied diseases, must lead to a more perfect classification. Upon the
basis of such trustworthy generalizations, we may hope ultimately to arrive at a more perfect knowledge of the causes which operate in the production of each, by successive elimination of those that are proved not to be essential, or, aa.they may be called, efficient causes.
But on this question we are not to enter. Our endeavor must be limited to laying down rules by which the student may be able to recognize at the bedside the diseases which he has been already taught in the schools. And however captivating the study of diagnosis must be to every thoughtful mind, dealing as it does with facts which can be more readily appreciated than those which result from the action of remedies; however gratify ing to the observer to call into legitimate exercise the highest mental functions, and to be enabled to pronounce a judgment upon the evidence presented to him, .which subsequent events shall prove to have been correct, it must still be remembered that this is but a means to an end. When elevated out of its true place, it only leads to the " mddecine expectante ;" which, boast ing of its knowledge of disease, either leaves the patient to die unrelieved or to struggle unassisted through his malady, or it raises the practitioner into a position of self-satisfied vanity, which, pretending to a kind of omniscience, causes him to overlook any fact or argument opposed to his conclusion, until death reveal how great and how fatal was the error. When neglected or despised, it produces that trifling treatment of symptoms arising in the course of a disease, when the more deep-seated or more distant cause for their production has been missed, and when unfortunately, both patient and practitioner are often deluded into the idea that a disease has been cured or eradicated, of which only the most prominent or most distressing symptoms have been alleviated.