External violence is, however, most commonly the cause of the change. In one case, the patient fell down stairs in a state of intoxication, striking the head on the steps. He continued in a state of insensibility for nine days, when he began to show signs of returning consciousness, taking food and drink, but memory, judgment, and all the mental faculties were gone. Death ensued in about two years. The dura mater of the left hemisphere was found greatly thickened. The pia mater infiltrated with a large amount of serous fluid. The convolutions were atrophied, and about four ounces of serous fluid found in the ventricles. The _fornix_ was softened and the _septum lucidum_ entirely destroyed. =Fibrinous Clots, or Thrombi=, will be occasionally found within the sinuses of the dura mater, where they may have given rise to congestion of the brain, with apoplectic effusions, paralysis, convulsions, coma, etc. They may originate from injuries of the head, inflammation of the dura mater, pulmonary disease, etc. =Tubercular Deposits= are also sometimes found in this membrane, appearing, however, mainly upon the arachnoid surface. They present the usual character of tubercle, having a whitish or grayish appearance, with the consistence of cheese, and scattered in small particles upon the surface. They are found in _tubercular meningitis_, (a disease common with children but rare with adults,) and in most of those cases of so-called acute hydrocephalus. =Tumors= of various kinds are occasionally found in the dura mater, including _cystic_, _fibrous_, _fatty_, _osseous_ and _cancerous_ growths. The latter may cause such absorption of the bones of the skull, as to appear on the exterior of the head. In one case which came into the dissecting-room some years ago, thin _bony formations_ of the size of a silver quarter dollar were found in the tentorium, and smaller ones in the falx cerebri. Nothing could be learned of the previous history of the case. 2. Arachnoid and Pia Mater. [=Notice= in examination, contents of cavity of arachnoid; serum or blood; if former, amount, color, odor; if blood, situation, quantity, fluid or coagulated; adhesion of surfaces of arachnoid; tubercles, their position, &c.; color of membrane; vascularity, transparency, or opacity. _Sub-arachnoid_ fluid—quantity, position, color, &c. _Pia mater_—vascularity, in points and entire; serous effusion into substance of; blood, &c.; position, size, &c., of clots; granulations, (tubercles,) number, position, &c.; Tumors—size, position, and character.] As morbid conditions of the arachnoid membrane are more common with its visceral layer, and as these conditions usually involve the pia mater, the two membranes are here noticed together. They will be found presenting various degrees of congestion after death, which will not necessarily be a positive indication of the extent of congestion during life.