1. The diagnosis of the symptom or symptom-group is to be made by—(_a_) careful inquiry into the manner of appearance, development, and chronological order of the symptoms as related by the patient or by his friends, and more especially by (_b_) an exact, and in some directions {62} minute, determination of the symptoms, obvious or latent, present in the patient. This valuable method of exact observation is sometimes, no doubt, carried to a ridiculous extreme, entailing much loss of time without corresponding results; but in medical practice, as in all forms of professional work, there enters a sort of genius, partly innate, but largely developed by cultivation, which enables the observer to seize at once, apparently by intuition or in the course of a few minutes of study, the really valuable and suggestive phenomena; and it is in this line, the line of important and correlated facts, that observation cannot be too minute and exact. In following this method technical terms must be correctly used and definitions rigidly adhered to, as superficial and loose records nearly always mislead. Sometimes in the course of the examination a symptom is discovered or a hint is thrown out by the patient which suggests new lines of inquiry, and occasionally necessitates an entire rearrangement of the data obtained. Consequently, it is important that the observer should approach a case tabula rasa, and should, as far as possible, prevent his being biassed by anticipations of, and immature guesses at, the third or final diagnosis. Besides exactness of observation, it is necessary that the physician should have a thorough knowledge of nervous nosology in order to complete the first diagnosis: he must be acquainted by book-study and by personal observation with the numerous types of symptom-groups which fill up our present classification of diseases, so that he can at once say, approximately at least, in what category the case before him belongs.