Diagnosis of Primary Syphilis.—­In cases in which there is a history of an incubation period of from three to five weeks, when the sore is indurated, persistent, and indolent, and attended with bullet-buboes in the groin, the diagnosis of primary syphilis is not difficult.  Owing, however, to the great importance of instituting treatment at the earliest possible stage of the infection, an effort should be made to establish the diagnosis without delay by demonstrating the spirochaete.  Before any antiseptic is applied, the margin of the suspected sore is rubbed with gauze, and the serum that exudes on pressure is collected in a capillary tube and sent to a pathologist for microscopical examination.  A better specimen can sometimes be obtained by puncturing an enlarged lymph gland with a hypodermic needle, injecting a few minims of sterile saline solution and then aspirating the blood-stained fluid.

The Wassermann test must not be relied upon for diagnosis in the early stage, as it does not appear until the disease has become generalised and the secondary manifestations are about to begin.  The practice of waiting in doubtful cases before making a diagnosis until secondary manifestations appear is to be condemned.

Extra-genital chancres, e.g. sores on the fingers of doctors or nurses, are specially liable to be overlooked, if the possibility of syphilis is not kept in mind.

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 spirochaete 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.