Definition.—­Virus.—­ACQUIRED SYPHILIS—­Primary period: 
    Incubation, primary chancre, glandular enlargement;
    Extra-genital chancres—­Treatment—­Secondary period:  General
    symptoms, skin affections, mucous patches, affections of bones,
    joints, eyes, etc.—­Treatment:  Salvarsan—­Methods of
    administering mercury—­Syphilis and marriage—­Intermediate
    stage—­Reminders—­Tertiary period:  General symptoms,
    gummata, tertiary ulcers, tertiary lesions of skin, mucous
    membrane, bones, joints, etc.—­Second attacks.—­INHERITED
    SYPHILIS—­Transmission—­Clinical features in infancy, in later
    life—­Contagiousness—­Treatment.

Syphilis is an infective disease due to the entrance into the body of a specific virus.  It is nearly always communicated from one individual to another by contact infection, the discharge from a syphilitic lesion being the medium through which the virus is transmitted, and the seat of inoculation is almost invariably a surface covered by squamous epithelium.  The disease was unknown in Europe before the year 1493, when it was introduced into Spain by Columbus’ crew, who were infected in Haiti, where the disease had been endemic from time immemorial (Bloch).

The granulation tissue which forms as a result of the reaction of the tissues to the presence of the virus is chiefly composed of lymphocytes and plasma cells, along with an abundant new formation of capillary blood vessels.  Giant cells are not uncommon, but the endothelioid cells, which are so marked a feature of tuberculous granulation tissue, are practically absent.

When syphilis is communicated from one individual to another by contact infection, the condition is spoken of as acquired syphilis, and the first visible sign of the disease appears at the site of inoculation, and is known as the primary lesion.  Those who have thus acquired the disease may transmit it to their offspring, who are then said to suffer from inherited syphilis.

#The Virus of Syphilis.#—­The cause of syphilis, whether acquired or inherited, is the organism, described by Schaudinn and Hoffman, in 1905, under the name of spirochaeta pallida or spironema pallidum.  It is a delicate, thread-like spirilla, in length averaging from 8 to 10 [micron] and in width about 0.25 [micron], and is distinguished from other spirochaetes by its delicate shape, its dead-white appearance, together with its closely twisted spiral form, with numerous undulations (10 to 26), which are perfectly regular, and are characteristic in that they remain the same during rest and in active movement (Fig. 36).  In a fresh specimen, such as a scraping from a hard chancre suspended in a little salt solution, it shows active movements.  The organism is readily destroyed by heat, and perishes in the absence of moisture.  It has been proved experimentally that it remains infective only up to six hours after its removal from the body.  Noguchi has succeeded in obtaining pure cultures from the infected tissues of the rabbit.