In the Joints, a serous synovitis or hydrops may occur, chiefly in the knee, on one or on both sides.

The Affections of the Eyes, although fortunately rare, are of great importance because of the serious results which may follow if they are not recognised and treated. Iritis is the commonest of these, and may occur in one or in both eyes, one after the other, from three to eight months after infection.  The patient complains of impairment of sight and of frontal or supraorbital pain.  The eye waters and is hypersensitive, the iris is discoloured and reacts sluggishly to light, and there is a zone of ciliary congestion around the cornea.  The appearance of minute white nodules or flakes of lymph at the margin of the pupil is especially characteristic of syphilitic iritis.  When adhesions have formed between the iris and the structures in relation to it, the pupil dilates irregularly under atropin.  Although complete recovery is to be expected under early and energetic treatment, if neglected, iritis may result in occlusion of the pupil and permanent impairment or loss of sight.

The other lesions of the eye are much rarer, and can only be discovered on ophthalmoscopic examination.

The virus of syphilis exerts a special influence upon the Blood Vessels, exciting a proliferation of the endothelial lining which results in narrowing of their lumen, endarteritis, and a perivascular infiltration in the form of accumulations of plasma cells around the vessels and in the lymphatics that accompany them.

In the Brain, in the later periods of secondary and in tertiary syphilis, changes occur as a result of the narrowing of the lumen of the arteries, or of their complete obliteration by thrombosis.  By interfering with the nutrition of those parts of the brain supplied by the affected arteries, these lesions give rise to clinical features of which severe headache and paralysis are the most prominent.

Affections of the Spinal Cord are extremely rare, but paraplegia from myelitis has been observed.

Lastly, attention must be directed to the remarkable variations observed in different patients.  Sometimes the virulent character of the disease can only be accounted for by an idiosyncrasy of the patient.  Constitutional symptoms, particularly pyrexia and anaemia, are most often met with in young women.  Patients over forty years of age have greater difficulty in overcoming the infection than younger adults.  Malarial and other infections, and the conditions attending life in tropical countries, from the debility which they cause, tend to aggravate and prolong the disease, which then assumes the characters of what has been called malignant syphilis.  All chronic ailments have a similar influence, and alcoholic intemperance is universally regarded as a serious aggravating factor.