It is important to bear in mind _the possibility of a patient having acquired a mixed infection_ with the virus of soft chancre, which will manifest itself a few days after infection, and the virus of syphilis, which shows itself after an interval of several weeks. This occurrence was formerly the source of much confusion in diagnosis, and it was believed at one time that syphilis might result from soft sores, but it is now established that syphilis does not follow upon soft sores unless the virus of syphilis has been introduced at the same time. The practitioner must be on his guard, therefore, when a patient asks his advice concerning a venereal sore which has appeared within a few days of exposure to infection. Such a patient is naturally anxious to know whether he has contracted syphilis or not, but neither a positive nor a negative answer can be given--unless the spirochæte can be identified. Syphilis is also to be diagnosed from _epithelioma_, the common form of cancer of the penis. It is especially in elderly patients with a tight prepuce that the induration of syphilis is liable to be mistaken for that associated with epithelioma. In difficult cases the prepuce must be slit open. Difficulty may occur in the diagnosis of primary syphilis from _herpes_, as this may appear as late as ten days after connection; it commences as a group of vesicles which soon burst and leave shallow ulcers with a yellow floor; these disappear quickly on the use of an antiseptic dusting powder. Apprehensive patients who have committed sexual indiscretions are apt to regard as syphilitic any lesion which happens to be located on the penis--for example, acne pustules, eczema, psoriasis papules, boils, balanitis, or venereal warts. _The local treatment_ of the primary sore consists in attempting to destroy the organisms _in situ_. An ointment made up of calomel 33 parts, lanoline 67 parts, and vaseline 10 parts (Metchnikoff's cream) is rubbed into the sore several times a day. If the surface is unbroken, it may be dusted lightly with a powder composed of equal parts of calomel and carbonate of zinc. A gauze dressing is applied, and the penis and scrotum should be supported against the abdominal wall by a triangular handkerchief or bathing-drawers; if there is inflammatory œdema the patient should be confined to bed. In _concealed chancres_ with phimosis, the sac of the prepuce should be slit up along the dorsum to admit of the ointment being applied. If phagedæna occurs, the prepuce must be slit open along the dorsum, or if sloughing, cut away, and the patient should have frequent sitz baths of weak sublimate lotion. When the chancre is within the meatus, iodoform bougies are inserted into the urethra, and the urine should be rendered bland by drinking large quantities of fluid. General treatment is considered on p. 149.