=Sanguineous Effusion—Apoplexy.= Effusions of blood may be found between the bones and dura mater; between the two layers of the arachnoid; within the substance of the pia mater; within the ventricles, or within the brain substance. Blood clots will seldom be found between the bone and dura mater, except as a result of mechanical injury, and in the majority of cases as an attendant upon fracture. If a fragment of the bone at the same time, be driven through the dura mater, then a clot may be found in the arachnoid cavity. But in another class of cases, where death has resulted from blows upon the head without producing fracture of the bones, the whole surface of the brain in the region of the injury, and not unfrequently in distant parts, after the removal of the dura mater, is found covered with a layer of blood, which at first sight appears to be outside of the membranes; but on close examination, it is found that the blood is effused or infiltrated into the sub-arachnoid tissue, and that it has escaped from the lacerated vessels in the pia mater. The thickness of the layer varies. It is generally in greater quantities at the sides and base of the brain, and the inferior lobes and cerebellum may be covered by it. It is usually thickest over the crura, the pons Varolii and medulla oblongata. In the same class of cases the blood may be also effused into the ventricles. These appearances are so uniformly the result of violence, as to form a valuable piece of evidence in medico-legal inquiries, to prove that such hæmorrhage and death could not be the result of internal causes. In the greater number of _still-born_ children, an examination of the head will show a similar condition of things. The surface of the cerebrum generally, with sometimes that of the cerebellum, will be found covered with a layer of coagulated blood effused into the pia mater, while the ventricles will often be filled with clots. Where the history of the case is not known, it might at first be suspected that death was the result of violence inflicted after birth. Violence has, to be sure, been the cause of death, but it is such violence as attends a protracted case of labor, with, perhaps, a large head, and a contracted pelvis of the mother. The wonder is, that from the great pressure to which the head is subjected during labor, that so few children are still-born or do not die soon after birth, from rupture of the cerebral vessels. Effusions into the ventricles, may also be frequently the result of external violence. The pia mater, the vascular membrane of the brain, we find carried into these cavities by means of the velum interpositum, which forms the roof to the third ventricle, while its borders extend into the lateral, forming the choroid plexuses. The effused blood may, therefore, extend along this membrane into the cavity of the ventricles.