In incipient inflammation, the membrane has a reddish tinge, a humid, succulent appearance, and there is more or less of a serous effusion, causing a slight separation from the bone. As the inflammation advances, the connection between the membrane and the bone becomes more lax, and the effusion assumes a purulent character. Syphilitic inflammation of the periosteum is apt to appear in detached spots, causing swelling, induration, the formation of new osseous matter and necrosis. The periosteum of the skull, sternum and tibia are most frequently attacked. A malignant disease of the periosteum, the consequence of long-continued or repeated attacks of inflammation, is described by Stanley. It occurs on the bones of the hips, and gives rise to the growth of a fungous excrescence upon the membrane. “This is sometimes soft and flocculent on its surface, with a firm, grayish, gelatinous base; at others it consists throughout of a firm, gelatinous substance.” Section II. OF THE BONES. [=Notice=: 1. _Surface of bone_—smooth or rough, firm and hard or soft; periosteum present or destroyed; caries; necrosis; tumors, etc. 2. _Whole bone_—weight and size increased, or diminished? bent or fractured? 3. _Appearance on section_—density of different portions; condition of cancellated portion; destroyed, or softened; abscesses; caries; necrosis; tumors, etc. 4. _Medulla_—density, color, vascularity, morbid growths.] =Inflammation and Abscess.= Acute inflammation rarely takes place except in connection with mechanical injury. Inflammatory processes in bone, give rise for the most part, to an increase of medullary tissue, and to softening of the osseous structure. Haversian canals and medullary spaces increase in size, and ultimately become confluent by the gradual absorption of the surrounding osseous lamellæ. The results of progressive inflammation are congestion, exudation, suppuration, caries and necrosis. An enlargement of the affected portion is invariably met with. In case the exudation be absorbed, or the inflammatory process be arrested, the parts may return to their normal condition, or the bone retains a permanently disorganized condition, which may present either an increased condensation and induration, as in gouty bone, or an abnormal rarefaction of the bone, as in the bones of rickety individuals. The same state of rarefaction, or _osteoporosis_, according to Lobstein, is occasionally met with in advanced life, as an effect of mal-nutrition. _Suppuration_, with the formation of _abscess_, may be diffused or circumscribed. In circumscribed abscess, we find a cavity generally in or near the epiphyses, lined with a vascular membrane, and thickening of the adjoining periosteum, and of the surrounding cellular tissue.