108 ANTHROPOLOGY. 



essential point from that of the spine : namely, in that it forms a periosteum 

 to the inner surface of cranial bones. It adheres closely to the whole 

 interior of the cranium, and the free communication between the vessels 

 of the dura mater and those of the bones serves materially to enhance the 

 connexion between this membrane and the osseous surface. On the roofs 

 of the orbits, the wings of the sphenoid bones, the petrous portions of the 

 temporal bones, the margin of the occipital foramen, and opposite the 

 sutures, the adhesion is very intimate. 



The cranial dura mater is not a simple bag. From its internal surface 

 partition-like processes pass inwards, which serve to separate certain subdi- 

 visions of the encephalon or brain. These are the falx cerebri, the tentorium 

 cerebelli, and the falx cerebelli. 



The falx cerebri is a process of fibrous membrane corresponding to the 

 mesial plane, and lying in the great median fissure of the brain, where it 

 separates the lateral hemispheres from each other. Its shape is falciform ; 

 its superior convex border corresponds to the frontal and sagittal sutures, 

 and incloses the great longitudinal sinus ; its inferior border is concave and 

 much shorter than the superior, and corresponds to the superior surface of 

 the corpus callosum, which connects the hemispheres of the brain. In front 

 the falx is narrow, and almost pointed ; it embraces the crista galli of the 

 ethmoid bone, which appears to be inclosed between its layers. The falx 

 cerebri contains within it, along its posterior border, a large vein, known 

 as the inferior longitudinal sinus. 



The tentorium cerehelli is continuous on each side with the posterior 

 border of the falx cerebri. This process is nearly horizontal in direction. 

 It forms a vaulted roof to a cavity, whose floor corresponds to the occipital 

 fossjB, and in which the cerebellum is lodged. The posterior and outer edge 

 adheres to the occipital bone, and to the posterior border of the petrous 

 portion of the temporal. The occipital portion of this edge contains a con- 

 siderable part of the lateral sinus, the portion adhering to the petrous bone 

 containing the petrosal sinus. The anterior or inner margin of the tento- 

 rium is concave, and free in the greater part of its extent. It is attached 

 by its anterior extremities to the anterior clinoid processes, to reach which 

 it crosses the posterior border. 



From the inferior surface of the tentorium cerebelli at its posterior edge, 

 a short and thick fold of very slight depth descends to the posterior edge of 

 the foramen magnum. This is the /ate cerebelli. It corresponds to the me- 

 dian notch between the hemispheres of the cerebellum. Its anterior border 

 is slightly concave. Two veins, called occipital sinuses, are contained in it. 

 J Although the internal surface of the cranial dura mater usually presents 

 the same smooth appearance as has been referred to in that of the spine, yet 

 an exception is found along the great longitudinal sinus, in the occasional 

 presence of small glandular bodies growing from the arachnoid membrane, 

 and causing a peculiar cribriform appearance in the dura mater. These 

 bodies, called glandulte or glands of Pacchioni, are in all probability not 

 normal structures, but are rather morbid products of the arachnoid produced 

 by continued cerebral excitement. 



814 * 



