The symptoms which mark the disease are as follow: The patient experiences in the evening a sensation of pain in the bone which is afterward the seat of the node. In the course of a few days, a swelling appears in the evening, which disappears again on the following morning. It is excessively painful and tender at night, but in the morning it is hardly perceptible, and the tenderness is almost gone. At this particular period the periosteum is only affected; but when the inflammation has continued some time longer, the bone is diseased and becomes enlarged. The rationale is this: An inflammation of the periosteum ensues. In a short time a deposite takes place between it and the surface of the bone. This deposite, in the first instance, is only a serous fluid, but a cartilaginous substance is soon secreted, which is gradually converted into bone. When attended to early, their treatment is very simple; but occasionally cases of considerable difficulty will arise. Large quantities of fluid will be found fluctuating between the periosteum and the bone, which, when unaccompanied by redness and inflammation of the skin, may be absorbed by proper treatment, but which more usually is only curable by evacuation; and, unless great care be used, exfoliation of the bone will ensue to a very great, and sometimes fatal extent. The eyebrows, forehead, and temples, are often the seat of fluid tumors varying from the size of peas and beans. Their cure must be effected by absorption, or destruction of the bone is often produced. The flat bones are also subject to syphilis. The one most commonly attacked is the _os frontis_, the symptoms being just the same as those on the skin. The side bones of the head now and then are affected; the os _occipitis_, or back-bone of the head, very rarely; and the _os temporis_, or temporal bone, being well covered with muscles, and exposed to very little change of temperature, is never affected. The _os frontis_, being the most exposed, is the most frequently attacked. Suppuration sometimes takes place; and when this has occurred on the front, it has happened that the same suppurative process has occurred interiorly between the _dura mater_, or the external membrane of the brain, and the internal surface of the bone. The matter presses upon the brain, and death is the consequence, if the pressure be not removed by the use of the trephine or trepanning instrument. This is a degree of severity to which the disease rarely reaches now-a-days, from the more extended knowledge and improved treatment of modern times.