=Increased Thickness= will also sometimes be found. This condition indicates _diminished pressure_ from within, as in atrophy of the brain. The thickening results from a gradual remodeling of the inner table and diploe, so that while the exterior of the skull may retain its normal size and form, the inner table following the retiring and shrinking brain, the interval between the two becomes filled with the thickened diploe. It has been observed that this hypertrophy is greatest at those parts of the bones where ossification first commences, as at the parietal and frontal eminences. It is not confined to old persons, though perhaps more frequent with them.[4] Section II. THE MEMBRANES OF THE BRAIN. 1. The Dura Mater. [=Notice= color and general character of surface; blood between it and bone; position of; quantity; coagulated or not. Condition of bone—necrosed or fractured; pus between dura mater and bone. Tumors—their position, size, &c. Wounds—their position, extent, &c. Open longitudinal sinus and note contents.] This membrane, serving both as a periosteum to the inner surface of the cranial bones and as a support to a serous membrane—the reflected layer of the arachnoid—is subject to affections of a two-fold character, those peculiar to the fibrous and serous portions. =Inflammation= of this membrane, may involve either the outer fibrous, or the inner serous layer. In the former case, the membrane appears congested, red and more or less softened. The inflammatory process may result in the formation of pus between the bone and dura mater, and even in gangrene. The disease may also extend to the adjacent portions of the pia mater and brain substance. External injuries, fractures of the bones of the skull, inflammation of the periosteum, otitis, resulting in caries of the temporal bone, may all be causes of inflammation of the outer portion of the dura mater. Inflammation of the inner surface of this membrane, is marked by the presence of a net-work of delicate red vessels, while the surface is covered by a soft, grayish or yellow semi-purulent matter, and may attend cases of pyæmic poisoning, puerperal peritonitis, or some of the exanthemata. =Thickening= of the fibrous portion of the dura mater may be found as a result of chronic inflammation, either spontaneous or as the result of external injury. From the identity of structure between this and other fibrous tissues of the body, it is not unlikely that this thickening is often the result of a rheumatic form of inflammation.