(From durus, hard, and mater, mother). It is so called from its hardness, compared with that of the pia mater, and from its being the source of all the other membranes; omenta eilamides, cuticu-laris membrana, and crassa meninx, to distinguish it . from the meninx tenuis or pia mater. See Pia mater.

The dura mater, to which dermatoides is used as an epithet, from its skin or leather-like appearance, lies contiguous to the inside of the skull; its substance is very compact; white, and glistening like a tendon, and divided into two or more lamellae. The external surface of this membrane is analogous to the internal surface of the periosteum in all parts of the body; it adheres more firmly to the cranium at the sutures than elsewhere, because of the vessels which run in these, and in the processes which are thrown out. The inner surface of the dura mater is, in general, a smooth membrane, and lies loose upon the pia mater, except at the sinuses, where they are attached by means 6f the veins which come out from the pia mater; and, sinking into the dura mater, form these cavities. The processes of the dura mater are divided into the external and the internal. The true external are those which line the foramina, which are afterwards lost in the pericranium, or accompany the nerves. These processes are accommodated, in general, to the size and direction of the nerves; but when the processes of the dura mater are mentioned, in general, the internal ones are meant. The longitudinal, or the processus falciformis, or falx (from its shape being like that of a sickle), begins at the crista galli; runs in the direction of the sagittal suture, to the middle of the os ocepitis, dividing, as already explained, the cerebrum into two hemispheres; it there forms two transverse processes, which lie between the two posterior lobes of the cerebrum and cerebellum. The glands of the dura mater, spoken of by some old anatomists, do not exist. The sinuses of the dura mater are venal, though their structure and form differ from veins; every section is triangular, and their shape like a prism. The veins are every where pouring their blood into these sinuses from all parts-of the brain, and there are several cords going across them, which, from their discoverer, are called chordae Willisii; but the veins and sinuses of the brain have already been described (see Cerebrum). The principal sinus runs along the processes. The dura mater appears more red than the tendons, because of the arteries which pass over its surface before they penetrate it. The arteries go from side to side, but do not open into the sinuses, as has been asserted. Wherever an artery runs upon the dura mater, it is accompanied with one or more veins, which contribute to make the sulci on the cranium, as well as the arteries. Its principal uses areas a covering for the brain; and it serves as an inner periosteum. The use of the processes is to connect the bones, and of the sinuses to retain the necessary proportion of blood.

The dura mater, when exposed in a living animal, is seen to have a pulsation corresponding to that of the arteries, owing to the systole and diastole of the arteries of the pia mater. When the dura mater is laid bare, it commonly sloughs like a tendon; in some cases it is ossified. The brain is sometimes protruded through the bregma in children, with its covering, the dura mater. Gooch, in his Medical Observations, gives an instance of a fractured skull, when a fluid being perceived under the dura mater, this membrane was cut through with the scissors, and the patient recovered.

The nerves have been said to arise from the fifth and seventh pair; but the modern anatomists do not acknowledge them.

Durae matris arteriae, and meninges. The dura-matral arteries. The external carotid artery sends a branch through the spinal hole of the os sphenoidale, which is the middle artery of the dura mater, and is called, by way of eminence, the artery of the dura mater. It is divided into many branches, which are dispersed through the substance of the external lamina as high as the falx, where these ramifications communicate with the branches on the other side. The impressions of this artery are seen on the inside of the parietal bones; the anterior and lower angle of which, instead of a simple impression, contain a canal for the passage of a trunk of this artery; on which account, several accidents happen in fractures of the skull.- The external carotid sends off another branch, through the superior orbitary fissure, to the dura mater, called its anterior artery; and it receives branches from the carotid and the vertebrals. Winslow calls the first mentioned of these arteries, spheno-spinalis. Dr. Hunter observes that the dura-matral artery proceeds from the inferior maxillary artery, and passes through a hole in the petrous part of the temporal bone.