=Diagnosis.=--Chancroid is likely to be confounded with _chancre_ and _herpes preputialis_. It has no period of incubation. Destruction commences after infection, so that within twenty-four hours macroscopic evidence may be observed, and within two or three days the sore has attained distinct size and shape. _Chancroid._ _Chancre._ _Herpes._ Local ulcer. First local sign of a Local neurosis. constitutional disease. A distinctly venereal Usually a venereal May be non-venereal, infection. infection. from friction, irri- tation, uncleanliness, etc. No incubation; lesion Incubation from ten to No incubation. noticed within a few seventy days before days. first lymphatic in- duration. Commences and remains Commences as a papule, Commences as a crop as an ulcer. or occasionally as an of vesicles. erosion. This _may_ ulcerate later. Usually multiple. Usually single. Multiple and occurring in crops or series. Secretion purulent Secretion slight and Little or no secretion. and abundant. serous or bloody. May occur again and As a rule, it only Patients who once have again. occurs once in the it are frequently same patient. subject to it. Auto-inoculable. Not auto-inoculable. Not inoculable. Phagedena frequent. Phagedenic action very Never. rare. Buboes in about 65 Bubonic enlargement Lymphatics rarely per cent. of cases. nearly always. involved. Buboes usually Buboes as a rule do suppurate. not suppurate. =Prognosis.=--Except in the most debilitated and dissipated, in whom phagedena may prove fatal, recovery always occurs, but often with the loss of tissue and disfiguring scars.