372 DURA. MATER. 



bones in the other parts of the body ; but is more firmly con- 

 nected at the sutures and foramina than elsewhere ; and so much 

 more firmly in children than in adults, that in separating it from 

 the cranium, it is apt to bring along with it some of the fibres of 

 the bone to which it is attached. In the adult, the separation 

 of the bone from the membrane is less difficult, in consequence 

 of many of the fibres being obliterated ; although in old age the 

 adhesion is sometimes very strong. 



The inner surface of the dura mater, which is remarkably 

 smooth, is in close contact with the brain, but adheres? only 

 where the veins go into the sinuses ; and is lubricated by a fluid 

 discharged through its vessels, which guards the brain from 

 danger, according as it may be affected by the different states of 

 respiration. 



The dura mater serves as a defence to the brain, and supplies 

 the place of a periosteum to the inside of the cranium ; giving 

 nourishment to it, as is evident from the numerous drops of 

 blood which appear after removing a portion of it from the 

 bone. 



The proper blood-vessels of the dura mater are not very 

 numerous. Its arteries are derived partly from the external 

 carotids, and partly from the internal carotids and the vertebral 

 arteries. Corresponding veins accompany these arteries; but 

 the dura mater by the separation of its two lamina forms also 

 reservoirs, that contain the venous blood, which is brought from 

 the substance of the brain. These are called sinuses, and are 

 very different from common veins. 



Nerves have been traced into the dura mater by the French 

 anatomists, derived from the sympathetic in the neck. There 

 have been disputes respecting its sensibility ; but there is reason 

 to believe that in a sound state it has very little. 

 Nervous fibrils have been likewise traced into the dura mater, 

 from the fourth pair and from several branches of the fifth. 

 The dura mater sends also a cylindrical prolongation through 

 the basilar foramen to the margin of which it is closely adhe- 

 rent, and down the vertebral canal, to enclose the medulla 

 spi.nali. It sends also tubular prolongations over each of the 



