Gummatous Infiltration of the Skin ("Syphilitic Lupus").—­This is a lesion, met with chiefly on the face and in the region of the external genitals, in which the skin becomes infiltrated with granulation tissue so that it is thickened, raised above the surface, and of a brownish-red colour.  It appears as isolated nodules, which may fuse together; the epidermis becomes scaly and is shed, giving rise to superficial ulcers which are usually covered by crusted discharge.  The disease tends to spread, creeping over the skin with a serpiginous, crescentic, or horse-shoe margin, while the central portion may heal and leave a scar.  From the fact of its healing in the centre while it spreads at the margin, it may resemble tuberculous disease of the skin.  It can usually be differentiated by observing that the infiltration is on a larger scale; the progress is much more rapid, involving in the course of months an area which in the case of tuberculosis would require as many years; the scars are sounder and are less liable to break down again; and the disease rapidly yields to anti-syphilitic treatment.

[Illustration:  FIG. 41.—­Ulceration of nineteen year’s duration in a woman aet. 24, the subject of inherited syphilis, showing active ulceration, cicatricial contraction, and sabre-blade deformity of tibiae.]

Tertiary lesions of mucous membrane and of the submucous cellular tissue are met with chiefly in the tongue, nose, throat, larynx, and rectum.  They originate as gummata or as gummatous infiltrations, which are liable to break down and lead to the formation of ulcers which may prove locally destructive, and, in such situations as the larynx, even dangerous to life.  In the tongue the tertiary ulcer may prove the starting-point of cancer; and in the larynx or rectum the healing of the ulcer may lead to cicatricial stenosis.

Tertiary lesions of the bones and joints, of the muscles, and of the internal organs, will be described under these heads.  The part played by syphilis in the production of disease of arteries and of aneurysm will be referred to along with diseases of blood vessels.

[Illustration:  FIG. 42.—­Tertiary Syphilitic Ulceration in region of Knee and on both Thumbs of woman aet. 37.]

Treatment.—­The most valuable drugs for the treatment of the manifestations of the tertiary period are the arsenical preparations and the iodides of sodium and potassium.  On account of their depressing effects, the latter are frequently prescribed along with carbonate of ammonium.  The dose is usually a matter of experiment in each individual case; 5 grains three times a day may suffice, or it may be necessary to increase each dose to 20 or 25 grains.  The symptoms of iodism which may follow from the smaller doses usually disappear on giving a larger amount of the drug.  It should be taken after meals, with abundant water or other fluid, especially if given in tablet form.  It is advisable to continue the iodides for from one to three months after the lesions for which they are given have cleared up.  If the potassium salt is not tolerated, it may be replaced by the ammonium or sodium iodide.