It has been the custom to speak of _urethritis_ as a synonym for gonorrhea, and to divide it into the specific and non-specific forms, including under the former expression cases where the gonococcus can be demonstrated, and under the latter term those which do not seem to show it. There is no doubt but that urethritis may be set up by the introduction of a foreign body, such as a sound or catheter, as well as by some irritating discharge from the vagina, and also as the result of excess of uric acid in the system, perhaps even of alcohol. These, if occurring in a previously uninfected urethra, may be regarded as distinctly non-specific lesions. It is also supposed that under certain circumstances inflammation may be set up by other organisms than the gonococcus; nevertheless almost all cases of so-called clap are positively gonococcus infections, simple or mixed, and have but one origin. =Diagnosis.=--_Diagnosis can be made positive only with the microscope._ A recognition of the gonococci by staining them and then watching the effect of iodine in their decolorization will be of great importance and reliable. The affinity of these germs for basic aniline dyes, and the fact that they do not take the iodine stain of Gram, will serve to differentiate them from the numerous other organisms with which they may be found mixed. By staining a cover-glass preparation first with methyl blue or other basic color, then placing it in Gram’s solution, and finally in a solution of Bismarck brown, the true gonococci which have been made visible by the methyl blue will have disappeared under the influence of the iodine, while other bacteria will be stained by it. It has been mentioned that the germ is a diplococcus of rather ovoid form, met in clusters but not in chains, and in groups of four or multiples of four; it may be attached to epithelium and pus corpuscles, or found within them, and is rarely found free in fluid except when present in large numbers. These organisms are capable of cultivation, growing best upon a mixture of human serum and neutral agar, at a temperature of 36° C. _The urethra may be infected from without and from within_, and this infection may be either of a truly specific type (gonococcus) or of the pyogenic type; as between these forms information may be gained by the history and the clinical course, but the minute diagnosis is only to be made with the microscope. This is of more than theoretical value, inasmuch as it substitutes a certainty for a working hypothesis. It is, moreover, sometimes of great value, as when the question of infection of one of the opposite sex comes up, or it may have at times even an important medicolegal value, as in cases of rape.