1. The period of primary incubation, or the time from infection to the appearance of the chancre. This is commonly three weeks.
2. The primary stage: the chancre forms and the neighbouring glands are affected. This stage lasts from three to ten days.
3. The secondary incubation, or the time between the appearance of the chancre and the development of what are called the secondary symptoms,—usually about six months.
4. The secondary stage. Here occur fever, anaemia, neuralgic pains, and the eruptions on the skin and the mucous membranes. This period lasts from twelve to eighteen months in the majority of cases.
5. The intermediate period. During this time there may be no symptom, or slighter recurrence of the secondary [{312}] symptoms. This period lasts from two to four years. It may end in recovery of health or be followed by tertiary symptoms.
6. The tertiary stage. In this period gummata form, or there may be diffuse infiltration of various parts of the body, chronic inflammation and ulceration of the bones, skin and other tissues, nervous diseases, and so on. The tertiary stage commonly begins from three to four years after the primary infection.
The three chief divisions, which are apt to blend one into the other, are the primary, secondary, and tertiary periods.
The affections of the secondary stage are often severe. There may be fever associated with weakness, headache, general malaise and pain, and this may be marked or rather light. In this stage iritis is liable to occur, and if it is not properly diagnosed and treated it will result in blindness.
The lesions of the tertiary stage may cause great destruction of tissues and very grave consequences. Cerebral syphilis, if unchecked, will inevitably cause paralysis or paresis. There may be loss of speech, epilepsy, coma, paralyses, apoplectic hemiplegia, and so on. The pain is harassing and often it amounts to great anguish. Whatever part of the brain substance is destroyed will not be restored.
In syphilitic affections of the spinal cord, if the inflammation is acute death ensues in a few days or weeks. Tabes dorsalis, or locomotor ataxia, is caused in about 93 per centum of cases of this disease by syphilis, and it is an incurable and dreadful malady.