[Sidenote: Diagnosis may be a source of danger] The primary purpose of diagnosis is to locate a difficulty, to find an internal disorder that is causing unpleasant symptoms. It will readily be granted that this is only desirable when, after the internal disorder has been located, we are able to do something to correct it; that otherwise it is of no more importance than to learn by post-mortem examination what caused death. Indeed, to know what the trouble is without knowing how to deal with it, is a very grave source of danger, and has caused many a death through resort to wrong methods. In a large percentage of cases Nature will heal, if her processes are not interfered with, and in all cases she is the real physician; our only proper office is to supply the right materials, and to leave her to use them as she will. [Sidenote: True diagnosis, merely an interpretation of Nature's language] Correct diagnosis is important because it is the guide--the beginning--the primary step in the treatment of dis-ease. Wrong diagnosis is usually followed by wrong methods of treatment, while correct diagnosis simplifies, and points the practitioner, with certainty, to the interpretation of Nature's language (symptoms). With an understanding of these, the remedy, in most cases, will suggest itself. [Sidenote: The human body and the linotype machine compared] The linotype machine that set the matter you are now reading is composed of several thousand parts. The keyboard is operated by the compositor, in much the same manner as that of a typewriter, and the delicate mechanism produces the metal lines of type ready to be "made up" in "forms" for the press. Where several such machines are in use, an expert machinist is usually employed to keep them in order. He can take them apart, study the mechanism at leisure, and reassemble them, yet it not infrequently happens that almost insurmountable difficulties are encountered. What would be the difficulties, then, if the machine were enclosed in a case that could not be opened, with only the keyboard exposed? What mechanical engineer in all the world could then make it work if something went wrong? One who could tell from the faulty action just what the matter was, and correct it from without, would be looked upon as a wizard. [Sidenote: Belief in the magical effect of drugs]